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DECT Shield for Arduino Electrical and Computer

1. essa 6 2 9 Arduino Wireless Shields dn ede dr rade d d e edere ER ders 7 2 4 iBithilum DECT Module oto M de ir ag dia M egg 9 2 5 External Network Interface iese ee ee ee ee ee ee ee ee Re ee de GR nennen nemen nnne nennen nnns 10 23 Implementation seas kale ete t EE EU de oed UR He Ud Ae aS 12 3 1 Iequirementsz s dote A e M ee te DE EIE 12 3 2 DECT Shield iine ee DE od eret ene n repe i d bee EE op denda ra 12 3 3 ei AE IE AE OE NE N OE OE EE OE 15 3 3 1 Bithium DECT Module Integration iese ee se ee ee Re ee Ge Re ee ee Re nnne 15 3 32 SB Interface EES e e od oed e e IR ee ed een ted ood hd 16 33 37 Audio Connectioris eor aa RHOD e P D e 21 3 3 4 Power Regulation and Distribution ee ee ee RA ee Re AR Re enne 23 3 3 5 Afduino shield Interface titi e d DR ee eek es 23 9 3 6 Circuit BOS Meier nehm 24 E MEET IE 28 3 4 1 8 he elt et EE feli Te e e eee ce ele EO e ee e e 28 3 4 2 Message Communication Protocol iese ee ee Re ee Re ee Ge Re ee Ge ener 29 343 Audio Playback 5r EE ER EE EE OE EE ER tes 30 3 4 4 External A sie SE VERRE AE OE OE EO EE OE HE as 31 Vi 3 475 AE N ARE ENE MO ME RE dt ea eet etaed tides 33 30 APpliCallons 5t tt ER N ls t Ske ER DES td tenes fenus 34 3 5 1 ON 34 3 5 2 Text to Speech iii A d ee ev NG De ut eda 36 3 5 3 Telephone aha 37 4 Shield Evaldation eel eden ee REM REMO RE RED ER 39 Fa Goncluslonhs ind o
2. Enabled Loudspeaker sConfigs sAudio sSpeaker bLoudspeakerEnabled true Apply configurations dect SetConfigs amp sConfigs TF was 73 Function Getstatus see Arguments None Return stStatus structure containing the current shield status Description The function returns the current shield status information inside a stStatus structure Please consult the contents inside the stStatus structure Code Example void loop lao Get shield status stStatus sStatus dect GetStatus Verifies if there is a file playing if sStatus sPlayback bPlaying true There is a file currently playing 72 NE 74 D 4 DECT GROUP FUNCTIONS This group includes the following functions e stInfo GetInfo void e stPincode GetPincode void e void SetPincode stPincode pPinCode e void SetPincode uint8 t n1 uint8 t n2 uint8 t n3 uint8 t n4 e void SetPincode uint8 t n1 uint8 t n2 uint8 t n3 uint8 t n4 uint8 t n5 uint8 t n6 uint8 t n7 uint8 t n8 e uint8 t GetList stListElem pList uint8 t nElements e bool Send uint8 t nIdentifier void pData uint8 t nSize e uint8 t Recv uint8 t pIdentifier uint8 t pBuffer uint8 t nSize bool Call uint8 t nIdentifier enum CallAction eAction uint8 t GetCallList stCallElem pList uint8 t nElements bool Register uint8 t nIdentifier bool Scan bool bEnable uint8 t GetScanList stScanElem pList uin
3. Note Function p is a serial printf void loop JUE wars uint8 t i j k stScanElem sList 10 i dect GetScanList sList 10 if dect LastError Print header Serial println Index RSSI RFPI if i 0 Serial println No fixed parts detected else Print detected fixed parts for j 03 j lt i j p d d 8 O2X 02X 02X 402X O2X n r j sList j nRSSI sList j nRFPI 0 sList j nRFPI 1 sList j nRFPI 2 sList j nRFPI 3 sList j nRFPI 4 else Serial println Failed if stats Remarks If the returned value is larger than the maximum number of elements then the shield returned more elements and some didn t fit in the vector 81 Function GetDECTStatus Arguments None Return stDECTStatus structure with the current DECT status Description This function returns the shield s DECT status This information can also be obtained using the GetStatus function Code Example void loop If sas Get shield DECT status stDECTStatus sStatus dect GetDECTStatus Prints the number of available data packets Serial println sStatus sData nDataPackets DEC LI s D 5 PLAYBACK GROUP FUNCTION This group includes the following functions void StartPlaying void void StopPlaying void void SetPlayVolume uint8_t nVolume stPlaybackStatus GetPlaybackStatus void bool OpenFile const char pFil
4. Opens 2 files and plays them in sequence dect SetPlaybackQueue 2 dect QueueFile musici wav dect QueueFile music2 wav dect StartPlaying ff Ass Remarks Current firmware version only supports 8 kHz WAV files with 8 bit u law encoding D 6 AUDIO GROUP FUNCTIONS This group includes the following functions void void void void void void void void EnableSpeaker void DisableSpeaker void EnableLoudspeaker void DisableLoudspeaker void SetSpeakerVolume uint8 t nVolume EnableMicrophone void DisableMicrophone void SetMicrophoneGain uint8 t nGain stAudioConfigs GetAudioConfigs void The description of each structure and function present in this group follows Function EnableSpeaker Arguments None Return Nothing Description This function enables the shield speaker output 84 Function DisableSpeaker Arguments None Return Nothing Description This function disables the shield speaker output Function EnableLoudspeaker Arguments None Return Nothing Description This function enables the shield loudspeaker output Function DisableLoudspeaker Arguments None Return Nothing Description This function disables the shield loudspeaker output Function SetSpeakerVolume Arguments nVolume Speaker attenuation from O to 7 Return Nothing Descri
5. Remarks If the returned value is larger than the maximum number of elements then the shield returned more elements and some didn t fit in the vector Function Register Arguments nIdentifier Identifier for the target shield to register Return If the function fails then it return false otherwise true Description This function has a dual functionality Fixed Part nIdentifier is true or false and the function enables or disables registration Portable Part The shield will attempt to register to a target shield referenced by the nIdentifier value 80 Function Scan Arguments bEnable Enable or disable scan Return If the function fails then it return false otherwise true Description This function only works when the shield is working as a Portable Part and it enables or disables the registration mode Remarks The Portable Part has to be in scan mode in order to be able to register Function GetScanList Arguments pList Pointer to a pre allocated vector of stScanElen structures nElements Number of elements in the pList vector Return Returns the number of elements written in the vector Description This function fills the pList vector with the list of detected Fixed Parts in range with their respective identifier and RSSI This function only works when the shield is working as a Portable Part Code Example
6. Sheet 2 2 53 B 2 BiLL OF MATERIALS Table B 1 Bill of Materials ltem Qty Value Device Parts Manufacturer Manufacturer Reference R EU R0603 R6 R7 PANASONIC ERJ3GEYJ1ROV A R EU R0603 R14 R15 PANASONIC ERJ3GEYJ100V Ea R EU_R0603 R4 R5 PANASONIC ERJ3GEYJ102V R1 R2 R3 R8 R9 R10 aa ae R EU R0603 R11 R12 R13 PANASONIC ERJ3GEYJ472V FEE ARE N CPOL EUUD 6 3X8 8 C1 C2 MULTICOMP MCESL35V226M6 3X5 2 6 1 tor CEUCOB05 MULTICOMP MCCA000268 C EUC0603 C6 C7 C14 MULTICOMP MCCA000530 ETES 100nF C EUCO603 C3 C4 C5 C10 C11 MULTICOMP MCCA000256 09 2 F C EUC0603 C12 C13 MULTICOMP MCCA000224 C EUC0603 C9 C15 C16 C17 MULTICOMP MCCA000192 LEDSML0805 LED1 KINGBRIGHT KPT 2012SURCK 74ABT125DB 74ABT125DB IC3 IC4 TEXAS INSTRUMENTS SN74LVTH125DBR 74AVC4T245PW 74AVC4T245PW TEXAS INSTRUMENTS SN74AVC4T245PW 74LVC1G125DBV 74LVC1G125DBV DIODES INC 74LVC1G125W5 7 REG1117 REG1117 NATIONAL SEMICONDUCTOR LM1117IMP 3 3 NOPB BDMR2 BDMR2 BDM1 BITHIUM BITHIUM DECT MODULE STEREO JACK STEREO JACK X2 X3 SWITCHCRAFT 35RAPC4BHN2 SDCARDM SDCARDM HRS HIROSE DM3D SF RESET SWITCH TE CONNECTIVITY FSM2JH 20 1 TERMBLOCK W237 102 CAMDEN CTB1202 2 21 2 F 1X06 SIP 100 40 J1 J3 SAMTEC ESQ 106 14 T S 22 2 F 1X08 SIP 100 40 J2 J4 SAMTEC ESQ 108 14 T S Pas AO MAO MULTICOMP MC34749 54 Table B 2 Component prices from Farnell Digikey and Mouser Farnell Farnell Farnell Min Refe
7. logic levels it is necessary to use a hardware interface circuitry Figure 3 1 DECT Shield architecture DECT Shield L Arduino Uno SPI Interface Bithium DECT zt E R1 R2 R3 Logic Module 3 microSD SPI is selected because of high transference rates 8 Mbps 50 Mbps 22 and 20 Mbps respectively and native support by all three devices The internal UART peripheral in the Arduino cannot be used because it is already reserved for the serial port and I2C 23 24 does not have enough bandwidth to transfer audio data Furthermore I2C has a maximum clock frequency of only 400 kHz and the communication protocol imposes an overhead The downside of SPI is requiring a 13 higher pin count and lacking error checking mechanisms when compared to other communication methods Arduino sketches have access to a library in order to interact with the shield the DECT API library This library provides a set of functions which are used to write Arduino applications using the shield The DECT API encapsulates the EIL to control the shield using commands and supports two programming models polling and events The BDM uses a proprietary DECT stack which is accessed using the External Network Interface The EIL in also included in the BDM firmware and uses the ENI to control the DECT stack and act accordingly to the commands received from the Arduino The conceptualized mechanism for transmission of generic data betwe
8. dectList Returns the list of known registered fixed portable parts 19 dectSend Send a chunk of data up to 54 bytes to a target shield 20 dectRecv Read one data chunk from the receiver FIFO structure 21 dectCall Make accept refuse or terminate a call to from another shield 22 dectCalllist Returns the list of all call channels indicating the state of each call 23 dectRegister Fixed Part Enable or disable shield registration mode in the shield Portable Part Register module to a target Fixed Part 24 dectUnregister Fixed Part Unregister a Portable Part from the module Portable Part Unregister the module from the current Fixed Part 25 dectScan Portable Part Enable or disable scanning mode for Fixed Parts 26 dectScanlist Portable Part Returns the list of Fixed Parts that were detected in range 27 dectStatus Returns the current DECT status information from the module Registration between shields requires at least one working as fixed part and another as portable part The fixed part enables registration using the dectRegister command and the portable part can scan for base stations using the dectScan and dectScanlist commands The portable part registers to the fixed part using the dectRegister command Both shields need to have the same pincode which can be set using the dectPincode command Figure C 1 illustrates the registration procedure 60 Figure C 1 Shield registration procedure Shield 1 Sh
9. frequencies to be used by the Arduino BDM and microSD card The analysis showed that the Arduino 20 can use its maximum frequency of 8 MHz when communicating with the BDM and the microSD card The BDM can use up to 14 7 MHz when accessing the microSD card due to delays imposed by the buffers and transceivers 3 3 3 AUDIO CONNECTIONS The shield is designed to include two mono audio jacks one to connect a speaker and another a microphone A headset with separated plugs can be connected to the shield using these jacks Figure 3 9 presents the schematic diagram of the audio filter and the speaker connection The audio is outputted from the BDM differential audio source connections LSRP and LSRN and allows to connect a speaker with an impedance of at least 28 O The two 10 pF capacitors are used to filter high frequency noise mainly from the DAC conversion The two 10 O resistors prevent damage to the BDM in case of short circuit The differential output has an impedance of 20 O that avoids any permanent damage Figure 3 9 BDM to speaker connections 10 LSRP Speaker LSRN 10 Bithium DECT Module 10p 10p Figure 3 10 presents the schematic diagram of the microphone circuitry and connection The BDM uses a variable voltage source to provide power on pins VREFp and VREFn and a comparator to detect the microphone vibrations on pins MICp and MICn The 10 pF capacitors filter high frequency vibrations the 1 KO resis
10. Bithium DECT Module Bill of Materials Dynamic Channel Selection DECT Standard Cipher Digital Enhanced Cordless Telecommunications Do It Yourself Data Link Control Layer Design Rule Check Digital Signal Processor External Interface Layer External Network Interface Frequency Division Multiple Access Fixed Part GNU Compiler Collection Gaussian Minimum Shift Keying Inter Integrated Circuit Integrated Circuit In System Programmer Interworking Unit Light Emitting Diode Lower Layer Management Entity Link Management Protocol Media Access Control Multiple Carriers Network Layer Printed Circuit Board Pulse Code Modulation Physical Layer Public Switched Telephone Network Portable Part Radio Frequency Subscriber Identity Module Serial Peripheral Interface Small Office House Office Radio Fixed Part Identifier xi RSSI TDD TDMA UART WAP WEP Radio Signal Strength Indicator Time Division Duplex Time Division Multiple Access Universal Asynchronous Receiver Transmitter Wireless Application Protocol Wired Equivalent Privacy xii 1 INTRODUCTION Today s world thrives on wireless communications ranging from practical Bluetooth headsets to the popular mobile phones During the past years the number of wireless capable devices has been growing rapidly and the range of applications has increased Nowadays they are used in areas which were mainly dominated by wired solutions for example in sensor netw
11. CA 94089 2003 36 Microsoft Microsoft Extensible Firmware Initiative FAT32 File System Specification 2000 37 J Capriotti FAT32 vs NTFS 2000 38 Microsoft Multimedia Programming Interface and Data Specifications 1991 39 AT amp T AT amp T Natural Voices Text to Speech Demo Online Available http www2 research att com ttsweb tts demo php Accessed July 2012 47 Appendix A SPI TIMING ANALYSIS In order to obtain high data transfer rates from the SPI bus it is necessary to determine the maximum SPI clock frequency fa supported by the SPI circuit that the Arduino BDM and microSD card can use The clock frequency depends on bo Maximum propagation delay of a buffer ty Maximum propagation delay of a transceiver e tado Maximum SPI clock active edge to data out delay tsetup Minimum SPI data in setup time The minimum period possible of the SPI clock is equivalent to the minimum time the master has to wait for an updated bit on the MISO line after a rising edge on the clock until a falling edge occurs The calculation of this value starts by taking into consideration the time required for the clock signal to go from the master to the slave ty In this project this value is given by 1 and consists of the propagation delay of each buffer and transceiver the signal needs to go through tpcik Neuf fers x i5 t Nrransceivers x fs 1 After the slave detects the clock signal the t
12. Consumption Range Stackable Bluetooth Shield 15 Limited Low Short XBee Shield 35 Limited Depends Depends WiFi Shield 70 Complete High Medium GSM GPRS Shield 60 Complete High Long 2 4 BiTHIUM DECT MODULE The Bithium DECT Module is illustrated in Figure 2 6 and was designed by Bithium It is a 63 pin board with a size of 39 3 mm by 30 6 mm and is based on the SC14CVMDECT 19 module with several modifications The module is capable of working as a DECT fixed part or as a portable part by changing the firmware Typical operation between devices is illustrated in Figure 2 7 The module requires a 3 3V power supply a few external bypass capacitors two filters for voice communication and an external antenna Figure 2 6 BDM layout and dimensions Bithium DECT Module revB 2 Depends on XBee model Additional costs for SIM card and carrier contract Figure 2 7 BDM typical communication Bithium DECT H Module Portable Part aq Voice 1 0 CI H Bithium DECT Bithium DECT E LA ue eis Voice Voice DI Fixed Part Portable Part HT 1 0 Bithium DECT HI Module Portable Part E Voice The core of the module is the SC14441A 20 operating at 1 8V This integrated circuit IC contains an integrated 1 7 to 1 9 GHz CMOS radio transceiver for DECT communications a programmable DSP for audio
13. DECTError Error code from the last API call Description This function returns the last error when communication with the shield Its value is changed every time an API function is called and if there is no error the returned value is O NoError Code Example void setup ET dect SetConfigs amp sConfigs if dect LastError NoError Communication error Lit ox Function Version Arguments None Return stVersion Version structure with the current firmware type and version Description This function is used to obtain the current shield version and to determine if it is working as a Portable or Fixed Part Code Example void setup V sss stVersion sVersion dect Version if sVersion nFirmType FP Shield is working as Fixed Part else Shield is working as Portable Part fL sas Function Reset Arguments None Return Nothing Description Resets the shield firmware to the default configurations Remarks All previously applied configurations are discarded Function Defaults Arguments None Return Nothing Description Resets the shield firmware to the default configurations and also resets the DECT module This means that the registration list the list of known parts and the pincode are erased and replaced with the original values Remarks All previously
14. For example in a standard 8 bit u law 8 kHz audio file being read at 10 Mbps it is necessary to read a new audio block of 512 bytes every 64 ms which takes approximately 4 1 ms The Arduino can use the remaining 59 9 ms to send a command as soon as the block finishes transferring FAT32 overhead is not taken into account in the example 3 4 5 DECT API LIBRARY The DECT API Figure 3 16 is a high level library that allows the Arduino to use the DECT Shield in sketches The library encapsulates the EIL and uses the command set with the Protocol layer to communicate with the shield More detailed information about the API functions is in Appendix D The library contains the functions necessary to retrieve status information execute operations and control the behavior of the shield There are functions to use the DECT components including registration and data voice communication to play files from the microSD card and to configure the external connections The components bellowing to the API e g variables functions interrupts are defined in a class included in the DECT h header file The class needs to be instantiated globally and is used to reference the DECT Shield Configurations to the Arduino are applied when the class constructor is executed and events can be enabled during the declaration Figure 3 19 exemplifies how the header and the class are declared in a sketch Figure 3 19 DECT API class declaration DECT Libra
15. data packet available in the shield See example below for more information Code Example void recvCallback uint8 t nIdentifier uint8 t pBuffer uint8 t nSize New data packet received nIdentifier Sender identification pBuffer Buffer with the received data nSize Number of bytes present in the buffer TODO Add processing code here void setup ae Set callback for incoming data packets dect attachRecvCallback recvCallback AE Remarks Event needs to be enabled using the SetConfigs function See the stEventsConfigs structure 88 Function attachCallCallback Arguments call Pointer to a callback function Return Nothing Description This function attaches a callback to the event triggered when there is a status change on one call See example below for more information Code Example void callCallback uint8 t nIdentifier enum CallState eNewState enum CallState eOldState 1 Call changed state nIdentifier Call Identifier eNewState New state of the call eOldState Old state of the call TODO Add processing code here void setup Ih s Set callback for when a call status changes dect attachCallCallback callCallback LT sak Remarks Event needs to be enabled using the SetConfigs function See the stEventsConfigs structure Function attachPlayb
16. file creation and file removal as well as opening files from a given path Files are read write in 512 byte blocks A file system facilitates copying files from a computer to a card without requiring special software and allows having multiple files organized by folders The most used file systems for flash drivers and memory cards are FAT32 and NTFS Both have advantages and disadvantages 37 but the FAT32 is selected because it is simpler has lower overhead and is already supported by the Arduino API WAV format 38 was chosen for audio files because it can contain uncompressed data in PCM or u law which can be sent directly to the BDM audio processor without software conversions A WAV interpreter that analyses the files and determines the play time the sample rate and the bytes per sample is implemented Current firmware supports only WAV files in 8 bit u law format at 8 kHz 3 4 4 EXTERNAL INTERFACE LAYER The External Interface Layer is responsible for verifying execute and respond to commands sent by the Arduino The EIL contains and manages the components that control the DECT Shield including the ENI section 2 5 the Protocol layer audio playback and events Detailed information about the commands defined in the EIL is present in Appendix C Figure 3 18 illustrates how the EIL is integrated with the remaining software components Messages received from the Arduino are separated in the Protocol layer and extracted comm
17. send data Each command has a specific operation associated and the protocol allows sending a payload related to the command The BDM is able to send similar messages to the Arduino in order to respond to previews commands or to transfer received data payloads from a DECT link for example The message protocol is fast and is implemented in the External Interface Layer EIL library which has mechanisms to avoid and mitigate communication errors To enhance the shield functionalities support for a microSD card was decided to be added This allows to store files and increases the number of possible application in which the shield can be used The BDM can open an audio file stream from one of the files inside the card and play it Additional functionalities such as audio streaming between shields or support for recording can also be implemented To improve playback performance it was decided to allow the BDM to access the microSD card directly without using the Arduino as an intermediary but also to allow the Arduino to access the microSD card if required A system to control the access to the card is implemented since more than one device will be able to use it Figure 3 1 presents an illustration of the DECT Shield architecture including the connections between the Arduino the BDM and the microSD which are made using SPI 21 The three devices are connected to the same bus as illustrated in the figure but since they do not have same voltage
18. Circuit Board 1 00 0 70 1 00 Total average price 22 06 9 66 22 43 The results present in the table show that the DECT Shield has a similar price to the XBee Shield but higher than the Bluetooth Shield which costs approximately half Although the prices are similar the DECT Shield contains a microSD slot and audio connections which are not present in the other 42 two shields The average price of 22 for the DECT Shield is within expectations considering the functionalities provided by the shield The microSD card slot and some of the logic associated with the interface does not require to be populated which can reduce the cost of the shield by approximately 1 50 resulting in a price of 20 56 43 5 CONCLUSIONS The main objective of this thesis was to specify design manufacture and assemble a DECT Shield using a Bithium DECT Module and to develop an easy to use library for Arduino Sketches are written using the library commanding the shield to register handle calls and transfer data to other compatible DECT devices The shields are double layered printed circuit boards and their components are common being easily acquirable Therefore the shield can be considered an undemanding Do It Yourself project that can be manufactured and assembled by hobbyists and independent developers The shield hardware including the schematic the layout the BOM and the Arduino DECT API are open
19. OVERVIEW Two major software components are developed in this project a DECT API library to be used by the Arduino sketches and a BDM firmware Both components consist of several abstraction layers in form of libraries that hide the implementation details and provide a set of functions for interfacing An overview of all the layers and the interface between them is presented in Figure 3 16 for two DECT Shields Layers in blue were developed by Bithium and green ones in this project Arduino sketches are represented in red Application 28 Figure 3 16 Software abstraction layers overview i f Bithium DECT Module Bithium DECT Module i Arduino i External Interface Layer External Interface Layer Arduino i da ES Application FAT32 ENI ENI FAT32 Application h Protocol y HAN Protocol DECT API EIL Micro SD Micro SD DECT API EIL i Protocol SPI Flow Control DECT Stack DECT Stack SPI Flow Control Protocol I N ae SPI SPI DECT Link SPI Low level communication between the Arduino and the BDM has similar abstraction layers including the SPI layer to send and receive messages containing the commands using buffers and the Protocol layer to generate decode communication messages The SPI Flow Control layer controls the SPI circuitry in the shield and is responsible to deliver payloads to the correct destination Arduino or microSD The DECT API library p
20. applied configurations are discarded 72 Function GetConfigs Arguments sConfigs Pointer to a stConfigs structure to hold configurations Return If the function fails then it return false otherwise true Description This function returns the current module configurations and blocks until the shield sends a response back which means that this function should always be the first to be called during setup Code Example void setup HI wes stConfigs sConfigs Wait until the module is ready dect GetConfigs amp sConfigs Verify if speaker is enabled if sConfigs sAudio sSpeaker bEnabled true Speaker is enable Eli Remarks This is the only function in the API that blocks until an answer from the shield is received Function SetConfigs Arguments sConfigs Pointer to a stConfigs structure with the configurations to apply Return If the function fails then it return false otherwise true Description This function applies shield configurations from a previously modified stConfigs structure It is highly recommended to obtain the current shield configurations with the GetConfigs function before modifying the structure Code Example void setup J ws stConfigs sConfigs Obtain current shield configurations dect GetConfigs amp sConfigs Disable Microphone sConfigs sAudio sMic bEnabled false
21. are used A description of the shield printed circuit board design is also provided The Production Dossier including the circuit schematics Bill of Materials BOM and layout Gerber files is in Appendix B 3 3 1 BITHIUM DECT MODULE INTEGRATION The BDM provides several types of interfaces and internal peripherals as already stated section 2 4 The DECT Shield uses the following e SPI for microSD card and Arduino communication explained in section 3 3 2 e UART for in system programming ISP and debugging e General purpose I O ports for shield control e Speaker and loudspeaker outputs for audio e Microphone input for audio capture The UART ISP connection allows to update the BDM firmware and provides a debugging interface without requiring a special programming device Any UART interface cable operating at 1 8 V can be used for this purpose such as a USB to UART converter A total of seven l O ports are used Four l O ports control the SPI interface One is used as a handshaking mechanism between the Arduino and the BDM mitigating synchronization problems and another is used to generate asynchronous events for the Arduino Finally an additional I O port is used as a current source to power a status LED Speaker loudspeaker and microphone interfaces are used to provide external connections for a headset and a low impedance loudspeaker Each connection has an on board audio filter to improve quality BDM output ports
22. connected to Arduino SPI signals SCK MOSI MISO and to CSS The four remaining buffers define the active SPI channel Control is performed by the BDM reducing the number of necessary Arduino pins By default the shield operates in Mode A In order for the Arduino to communicate with the BDM it has to assert the DSS pin The BDM changes the shield operation to Mode B and asserts the READY signal informing the Arduino to start transmitting The READY signal is used as a synchronization mechanism to prevent the Arduino from sending commands before the BDM is ready Figure 3 6 Figure 3 7 and Figure 3 8 illustrate all three possible SPI channels in green In Mode A there is always a channel defined connecting the BDM to the microSD card In Mode B a channel is created based on the selection pins CSS or DSS Asserting CSS creates a channel connecting the Arduino to the microSD card and asserting DSS connects the Arduino to the BDM 18 Figure 3 6 SPI buffers in Mode A BDM connected to microSD Arduino 1 READY BM D Master Micro SD Slave Arduino 0 READY BM D Slave CTRL2 1 Micro SD Slave 19 Figure 3 8 SPI buffers in Mode A Arduino connected to microSD 0 em zo N LX e AA Ad CTRLZ m7 Y po VEE ane as csk d SE Q v F BE I
23. documentation The main goal of this work is to conceptualize implement and test an Arduino shield containing a Bithium DECT Module BDM This includes the development of the BDM firmware code the API for the Arduino the printed circuit board PCB a set of application examples and the documentation The specific objectives to be achieved are e Toanalyze commercially available wireless shields for Arduino e To analyze the Arduino and the BDM specifications e To specify design manufacture and assemble the DECT shield e To specify and implement the necessary software components e To test the shields using a set of application examples e To write the thesis This thesis is organized in five major chapters Chapter 2 describes the technologies and devices used in the project It also includes a description of existing wireless shields for the Arduino The hardware and software implementation including the decisions and the applications developed are described and explained in detail in Chapter 3 Tests performed to verify the shield performance and the results obtained are discussed in Chapter 4 Finally Chapter 5 contains the project conclusions and presents some suggestions for future work and improvements 2 TECHNOLOGIES AND APPLICATIONS 2 1 DECT DECT 5 is a standard specified by the ETSI for wireless communications developed in Europe in 1992 Some of DECT standard characteristics are present in Table 2 1 Table 2
24. dr ID Data Receive one data packet Call dc ID Data Ok Fail Make accept refuse or terminate DECT a call Call List dcl Call List Get call information list On Off Enable registration for FP or Register dreg ID Action ran register PP Unregister dureg Ok Fail Unregister from current module Scan dscan On Off Ok Fail Enable or disable scan on PP Scan List dsl Ok Fail Get the list of scanned modules Status dst DEG Get the DECT status Status Play pbp Plays the opened file or queued sequence Stop pbs Stops playing Volume pbv 0 15 Changes the volume 0 15 Playback Playback Playback Status pbst Status Gets the playback status Open File pbo File path OK Fail Opens a wav file from SD Card Queue Size pbqs Size OK Fail Changes the playback queue size Queue File pbqf File path OK Fail Queue a file to be played Speaker as On Off Enable or disable the speaker Loudspeaker als On Off Enable or disable the loudspeaker Speaker gt 0 7 Change the speaker volume 2dB Audio Volume to 12dB in steps of 2dB Microphone am On Off Enable or disable the microphone Microphone pS 0 15 Change the microphone gain Gain 9 OdB to 30dB in steps of 2dB 1 Audio Gets the audio current Configurations acfg E E Configs configurations Allows the Arduino to access the Access sdacc Memory microSD card Card Releases the microSD card from Release sdres the Arduino 3 5 2 TEXT TO SPEECH This appli
25. encoding and decoding analog and audio interfaces with internal DACs and ADCs a Class D amplifier for 0 5W loudspeakers a power management circuit and several standard connections such as I O ports UART SPI I2C and PCM This IC also contains a 16 bit CR16Cplus general processor operating at 82 944 MHz that is used to control the components inside the chip The processor runs a custom firmware that can be easily changed using an internal boot loader through the serial port The firmware is stored in a 2 MB Flash Memory IC present in the module that is connected to the SC14441A thought a Quad SPI interface 2 5 EXTERNAL NETWORK INTERFACE The External Network Interface layer is an API developed by Bithium which interacts directly with the DECT stack allowing to perform several operations regarding DECT in a standardized way This includes handling calls data packets and the registration process for example The programming method employed by the API consists in an event base system which has an idle loop where non critical and non DECT related code is executed and several user defined callback functions related to DECT mechanics The callbacks are executed asynchronously when a DECT operation is executed or when there is a new status update for example 10 The event based programming model used in the ENI has many advantages when working with user interfaces such as buttons or LCDs because certain elements only need to be updated
26. or changed when a DECT event occurs It is also very good because it encapsulates all DECT related components and makes them easy to access and process However it is difficult to create time critical applications for example This API works for fixed parts as well for portable parts but both cases cannot coexist in the same firmware due to the way it is implemented In order for the BDM to work as fixed part and portable part a dual boot system can be created using two separated compiled binaries 11 3 IMPLEMENTATION 3 1 REQUIREMENTS The main goal of this project is to develop a shield that allows the Arduino to use the functionalities supported by the Bithium DECT Module The shield needs to be competitive enough to compete in a market already lead by shields for other wireless technologies It must be cheap easy to use and support attractive functionalities for wireless applications The DECT Shield is conceptualized after analyzing the DECT specifications the BDM the Arduino and the commercially available wireless shields in Chapter 2 A list of requirements is presented e Use of Bithium DECT Modules for DECT operations e Ability to use the shield as a DECT fixed or portable part e Ability to perform DECT calls and data transfers between shields e Ability to reproduce and transmit an audio stream e Support for a headset and a loudspeaker e Ability to regulate speaker volume and microphone gain e Support for bidire
27. source The source code of the BDM firmware uses proprietary libraries and could not be distributed However the BDM can be updated using the shield ISP port and a binary file containing the firmware All resources were made available online in the Arduino forums and positive responses were received For audio communications the shields support a headset microphone and speaker through two standard 3 5mm jacks and a low impedance loudspeaker There is also an on board microSD card slot which the Arduino and the BDM can access to store files The shield can play audio files stored in the card using the speaker or and the loudspeaker There were some difficulties when attempting to integrate the ENI with the Protocol and the microSD layers where no user interfaces are used nor callbacks required Both layers are time critical and hard to adapt to an event based system which resulted in a mild impact in performance All functionalities supported by the software were tested in crowded and non crowded DECT environments using the three test applications developed for this purpose All features present in the shields are covered by these applications and work as expected allowing to play files register DECT devices and to transfer data and audio wirelessly The shield cost and supported functionalities are within expectations being able to compete with existing short range range shields using Bluetooth and ZigBee During the course of this
28. the library in an Arduino sketch Firstly the library is initialized by creating a global instance of the DECT class where the communication ports used by the 63 shield are initialized Secondly the shield is configured in the setup function e g speaker volume DECT pincode Finally control code e g make call analyze data payload can be executed in the sketch loop function to manage the shield components Figure D 2 DECT API library sketch flow setup loop Class Initialization Shield Configuration Shield Operations Initializes variables y E g Volume E g Send Receive SPI bus and I O Microphone gain data make calls ports DECT pincode etc etc Figure D 3 shows an empty sketch with the necessary code to use the DECT Shield The first instruction creates an instance of the DECT class The argument with the false value indicates that events are not used in the sketch To configure the shield it is necessary to call the GetConfigs function in order to retrieve the configuration structure from the shield The structure contains the current configurations and can be changed to obtain the intended shield behavior New configurations are applied after sending the structure back to the shield using the SetConfigs function Figure D 3 DECT Shield empty sketch for Arduino DECT Shield Empty Sketch include lt DECT h gt DECT class WITHOUT events true fo
29. to a target DECT device To read an incoming data packet it is necessary to use the Recv function The total number of incoming packages present in the shield can be retrieved using the GetStatus or GetDECTStatus functions The library can be configured to generated and event when a new packet arrives automatically transferring the packet to the Arduino Figure D 4 contains a code snippet exemplifying data transference Figure D 4 Arduino exemplification code for data transference void Loop Ju acs Send a string to all registered DECT devices char pString 54 Hello dect Send 0 pString strlen szString 1 LI avs Read an incoming packet uint8 t nIdentifier Sender identifier uint8 t nPacketSize dect Recv amp nIdentifier pString sizeof pString Th sca Calls are handled using the Call and GetCallList functions GetCallList returns a list of the voice communication status or calls of each registered part using the identifiers obtained from GetList The calls can have three different states e No Call no call established When a call is refused or terminated it goes to this state e Pending waiting for an answer If the call is outgoing then it is waiting for the destination to answer otherwise it is waiting for the user answer A call in this state can be refused or accepted e Ongoing communication established The audio channel between the two devices is formed voice communication is pos
30. to filter interferences Bypass capacitors are located near each IC and the pull up resistors are placed close to the BDM output pads All ICs resistors and capacitors used are SMD in order to conserve circuit area Free circuit areas left with cooper are connected to Ground in order to improve power distribution between the shield components The layout passed the DRC verification without errors and some PCBs were ordered from Eurocircuits Figure 3 14 presents the DECT Shield fully assembled 26 Figure 3 14 DECT Shield assembled y ZA TE TIER ING pend gt a After some tests there was a few problems detected these are corrected in revision B e Changed the shield power pin from the Arduino Vin to the 5 V pin The Vin can only be used if the Arduino is powered by an external source and the 5 V provides power regardless of the source e g USB e Added a missing connection from the BDM VBAT pin to the 3 3 V power regulator e The size of some traces was reduced For example the connections to the loudspeaker Figure 3 15 shows the final layout More information is in the Production Dossier presented in Appendix B 27 Figure 3 15 DECT Shield layout rev B 3 4 SOFTWARE The next sections describe the software components and explain the implementation details Detailed documentation of the libraries developed including functions structures and usage is present in Appendix C and Appendix D 3 4 1
31. to where to send the data pData Pointer to a byte array containing the data to send nSize The size of the data array Return If the function fails then it return false otherwise true Description This function sends a data packet with up to 54 bytes to another shield using DECT The nIdentifier argument identifies the target shield Remarks nIdentifier can be obtained from the GetList function Function Recv Arguments pIdentifier Pointer to a pre allocated byte to write the sender identifier pData Pointer to a byte array to write the received data packet nSize The maximum size of the data array Return The total size of bytes received is returned Description This function can be called when there is a received data packet in the shield in order to transfer it to the Arduino 78 Function Call Arguments nIdentifier Shield identifier Call channel to where to send call action eAction Call action to be executed Return If the function fails then it return false otherwise true Description This function executes a call action on a target shield It can used to make refuse or terminate a call for example Code Example void loop J ss Call all known Portable Parts dect Call 0 MakeCall E Remarks The identifier O corresponds to all registered parts Call channels can be obtained using the GetCallList function 79 Fun
32. 1 DECT characteristics from 5 Frequency band 1880 1900MHz Number of carriers 10 Carrier spacing 1 728 MHz Access technique TDMA TDD FDMA Traffic duplex channels 12 Data rate per channel 32 kbps Range 30 mor 300m Modulation GMSK BT 0 5 Sensitivity 86 dBm at 0 01 BER Average RF power slot 10 mW Peak RF power 250 mW DECT typically works in star topology as a micro cell system formed by base stations FPs Fixed Parts and portable terminals PPs Portable Parts In order for a cell to exist it requires a base station and at least one portable part which the station will serve These cells are generally connected to each other through Public Switched Telephone Networks PSTN DECT defines the radio interface between the portable parts and the fixed part as represented in Figure 2 1 Figure 2 1 DECT star topology PP DECT relies on a method called Dynamic Channel Selection DCS for the channel allocation procedure 6 Instead of using a fixed channel for communication the portable parts are continuously sensing the available channels and trying to use the best one This method relies on the portable parts to select the channel instead of the fixed part The portable terminal chooses the least interfered channel from a periodically updated list of all 120 existing channels DECT is also capable to handover time slots in order to improve communication qu
33. 1Byte Message Header Message Payload Message Termination Each message has the following elements e Message Header Information about the command inside the message and the total size o Start of Message SOM Indicates a start of a new message o Command ID Identifier of the command present in the message o Body Size Size of the payload associated with the command 0 to 255 e Message Body Contents of the command inside the message up to 255 bytes e Message Termination Information to detect errors in the messages o Checksum Sum of all bytes in the header and in the payload o End of Message Indicates the termination of the message The messages have a minimum length of 5 bytes and a maximum of 260 bytes depending on the command payload An overhead of 4 bytes is present in each message SOM Body Size Checksum and EOM The SOM and the EOM are used by the protocol to detect when the SPI library returns a start or an end of a message instead of dummy or invalid data The Protocol library records a message when a SOM is received and stops when an EOM is detected when Body Size 5 bytes are read or when a timeout is triggered The checksum is used to verify if a received message contains errors A message is considered valid if the correct message length is read starting from the SOM to the EOM and if the checksum calculated locally is equal to the received Valid messages are sent to the EIL in order to execute t
34. CPU cycles to emulate the interface A test showed the data rate is not enough to play an 8 bit 8 kHz uncompressed audio file from the microSD card producing gaps in the audio stream The emulated SPI cannot be connected to the Arduino and operate as slave because it does not have enough reaction time to latch incoming bits synchronously with the clock The selected solution consists in sharing a single SPI bus between the Arduino BDM and microSD card This method provides high data rates but requires external tri state buffers and transceivers to route the necessary SPI signals to the Arduino or to the microSD card forming a channel Additional control signals are also required to operate the buffers 16 Figure 3 3 illustrates the possible SPI channels between the Arduino BDM and microSD card The Arduino always operates as master the microSD card as slave and the BDM changes from slave when receiving data from the Arduino to master when accessing the microSD card Additionally the channels connecting the Arduino to the shield have to be in tri state when the BDM is accessing the microSD card allowing the Arduino to communicate with other shields using SPI Figure 3 3 SPI communication channels between the Arduino BDM and microSD card Arduino 5V 3 3V Bithium DECT Module microSD 3 3V 1 8V Two distinct modes of operation can be identified named Mode A and Mode B because the BDM cannot op
35. Dialog Semiconductor SC14441 SC14442A 1 8V Single Chips for DECT with RFPA and OSPI 2011 21 Microchip SPI Overview and Use of the PICmicro Serial Peripheral Interface 2002 22 Transcend microSDHC Card series 2009 23 Freescale M68HC11 Reference Manual 2007 24 NXP Semiconductors I2C bus specification and user manual 2012 25 Fairchild Semiconductor I2C Translator Pull up Resisters Internal vs External 2010 26 Texas Instruments SN7ALVTH 125 3 3 V ABT Quadruple Bus Buffers with 3 State Outputs 2003 27 Texas Instruments SN74AVC4T245 4 Bit Dual Supply Bus Transceiver with Configurable Voltage Translation and 3 State Outputs 2005 28 Philips Semiconductors Bi directional level shifter for I2C bus and other systems 1997 29 National Semiconductor LM1117 LM11171 800mA Low Dropout Linear Regulator 2006 30 Silicon Labs C8051FXXX Printed Circuit Board Design Notes 2006 31 Diodes Incorporated 74LVC1G125 Single Buffer Gate with 3 State Output 2012 32 CadSoft Online Available http www cadsoftusa com Accessed April 2012 33 Eurocircuits PCB Proto Online Available http www eurocircuits com images stories ec09 ec pcb proto overview english 1 2010 v3 paf Accessed April 2012 34 Cypress Top 10 EMC Design Considerations 2011 35 SanDisk SanDisk Secure Digital Card Corporate Headquarters 140 Caspian Court Sunnyvale
36. Figure 3 21 Telephone sketch state diagram PES X Menu dle Incoming d f Target pen Ee S K y e Ringing Calling A Jf End q 1S Acccept Call Talking LY Waiting j Acccepted p bc The sketch uses exclusively events and the states change when a new event is triggered e g keyboard input call accepted The applicant can be on one of the following states e Menu Arduino is idle and the user can receive or make calls e Calling Waiting for the user to select a target Arduino from the contact list e Waiting Waiting for the target Arduino to accept or refuse the call e Talking Call is undergoing waiting for the user or the target to hang up 37 e Ringing Incoming call detected user needs to accept or refuse the call Data transferences are used when one telephone wants to know the name of another Names are used to identify other shields running Telephone when the application switches to Calling state showing the number and names of known parts 38 4 SHIELD EVALUATION To verify the shield correct operation some tests were executed using the three applications developed section 3 5 and additional operation specific sketches targeted for debugging It is possible to test the shield performance regarding range transmission rates responsiveness and consumption Some comparisons with existing shields are also performed
37. File is valid sews Function OpenFile Arguments pFilePath String with the file path and name in the memory card to open Return If the function fails then it return false otherwise true Description This function opens an existing audio file from the memory card This function always resets the playback queue size to 1 Code Example void loop Li eas Open file and play it dect OpenFile music wav dect StartPlaying I wes Remarks Current firmware version only supports 8 kHz WAV files with 8 bit u law encoding 83 Function SetPlaybackQueue Arguments nSize New size of the playback queue Return If the function fails then it return false otherwise true Description This function changes the size of the playback queue Its size represents the maximum number of files that can be loaded and played in sequence Remarks The shield will only set the intended size if it was enough memory to do so Function QueueFile Arguments pFilePath String with the file path and name in the memory card to open Return If the function fails then it return false otherwise true Description This function opens an existing audio file from the memory card and places it on the bottom of the playback queue If the queue is full or the file is invalid the function will return false Code Example void loop II wes
38. International Standard 1994 8 A Gl ria ZBeeMeR Instituto Superior T cnico INESC ID 2010 9 Arduino Arduino Official Site Online Available http arduino cc Accessed May 2012 10 Atmel megaAVR Online Available http www atmel com products microcontrollers avr megaavr aspx Accessed May 2012 11 H Barrag n Wiring Online Available http wiring org co Accessed May 2012 12 J Oxer Arduino Shield List Online Available http shieldlist org Accessed June 2012 13 Arduino Arduino Uno Online Available http arduino cc en Main ArduinoBoardUno Accessed May 2012 14 ITead Studio Stackable Bluetooth Shield Online Available http iteadstudio com store index php main page product info amp products id 307 Accessed June 2012 15 Digi Digi XBee Wireless RF Modules Online Available http www digi com xbee Accessed June 2012 16 Arduino Arduino WiFi Shield Online Available http arduino cc en Main ArduinoWiFiShield Accessed August 2012 17 B Landoni GSM GPS shield for Arduino Online Available http www open electronics org gsm gps shield for arduino Accessed September 2012 18 Micron Electronics Sim900 GSM GPRS EGSM Module Online Available 46 http www simcom us product_detail php cid 18pid 37 Accessed September 2012 19 Dialog Semiconductor SC14CVMDECT Cordless Voice Module 2011 20
39. P and the DECT circuitry inside the BDM are not fully activated until the creation of an audio channel or until a DECT transmission is executed Measurements show the on board regulator dissipates approximately between 15 mW and 96 mW that is within expected values When comparing the transmission consumption with the Bluetooth Shield which consumes approximately 20 mA and with the XBee which consumes 35 mA it is possible to conclude that the DECT Shield consumes similar amounts of current when working as a portable or as a base Manufacturing Costs Table 4 2 presents the price estimation from the BOM of the DECT Shield Bluetooth Shield and XBee Shield for comparison The average prices were obtained from Mouser website at high quantities price of 5000 units for passive components 1000 units for semiconductors and 1000 units for connectors The prices for the printed circuit boards were obtained at quantities of 300 from Iteadstudio Calculating the approximate shield costs from the BOMs allows to do a fair comparison without using market value prices Table 4 2 Shield cost estimation from BOM Component family DECT Shield Bluetooth xBee Shield Shield Passive components e g resistors capacitors 0 28 0 10 0 31 Integrated circuits 1 32 0 00 1 21 Module DECT Bluetooth XBee 15 00 6 91 17 00 Connectors e g audio jacks header 4 46 1 95 2 91 Printed
40. SPI communications in the shield are a major concern of this project The Arduino BDM and microSD work at different voltages and their SPI interfaces operate differently as presented in Table 3 1 In the Arduino SPI data pins change direction based on the mode of operation for example the MOSI pin operates as output when the Arduino is master and as input when slave The BDM and the microSD card pins do not change direction These differences imply the SPI bus cannot be connected to all three devices directly Table 3 1 SPI pins for Arduino BDM and microSD card SPI pin Arduino Master Arduino Slave BDM Master BDM Slave microSD SPI Clock SCK output SCK input SCK output SCK input SCK input SPI Data Out MOSI output MISO output DO output DO output DO output SPI Data In MISO input MOSI input DI input DI input DI input SPI Select N A CSS input N A DSS input CSS input SPI Voltage 5V 3V inputs 5V 3V inputs 1 8V 3 3V 1 8V 3 3V 3 3V The BDM has only one SPI interface Therefore it is not possible to connect the BDM to the Arduino and to the microSD card using separated busses Two different approaches are developed and tested to solve this problem Firstly generic VO ports are used to emulate a SPI interface connecting the BDM to the microSD card This solution proved to be inefficient The maximum data rate is 350 kbps and requires several
41. SPI signals in Mode 2 SS tmin X tak v Y M y wo Yi XY RES gt ct H ET ZW IRIS ER ae te X The first maximum SPI clock calculated is for when the Arduino is communicating with the BDM In this case the Arduino is in master operation and the module is in slave The clock signal needs to go through one buffer and one transceiver and the data out line DO from the BDM goes through two buffers and one transceiver Using the timings present in Table A 1 and the three equation system formed by 3 4 and 5 the maximum clock speed is calculated 1 AM M LLLA 116MH 3 lek 3x 84ns 12 5ns 123ns 10n5 Ek tj tt 39ns 4 5ns 8 4ns 4 bio 2 Xt t 2x3 9ns 45ns 123ns 5 Since the SPI communication channel between the Arduino and the module allows speeds up to 11 6 MHz and the Arduino SPI interface can work at a maximum frequency of 8 MHz it means that there should be no issues if the maximum frequency is used The second clock calculated is for when the Arduino is accessing the memory card Both the clock signal and the microSD DO only need to go through one buffer No transceivers are used in this communication channel Equations 6 7 and 8 form the system to calculate ja 49 1 A SD 8 EE m 15 7MH 6 fai 2 x 3 9ns 14ns 3 9ns 10ns 7 6 tsak th 3 9ns 7 DER t 3 9ns 8 The full bandwidth of the Arduino SPI interface can be used because the ch
42. SS 1 TAABT1250B 3 A MISO D IC3A 74ABT125DB T4ABT125DB E 3 74ABT125DB IC4A m IC4D 12 74ABT125DB 11 74ABT125DB Rev B In cooporation with Bithium IST 8 INESC ID Marcelo Vicente DECT Shield 28 08 2012 14 45 21 Sheet 1 2 IST 5 6 52 Figure B 2 DECT Shield schematic 2 of 2 REG1117 VIN OUT z 74LVC1G125DBV RST VBAT soc DC_SENSE DC CHARGE CTRL DC CTRL DC CTLN LSRP LINEOUT AGND Place near IC3 STEREO JACK C16 1 LSRN LINEOUT AGND ULP VBAT MICP CIDIN ULP MAIN MICN CIDOUT ULP XTAL MICHILINEIN ULP PORT VREFP VREFM CP_VOUT1 CP VOUT2 POO UTX WLED_CURO Te x 10p GND GND STEREO JACK POT URX PWMO WLED CUR1 PO4 SPI EN POS SPI_CLK P20 LED3 PWMO ECZ1 POS SPI DO P21 LEDA PWM1 ECZ2 P07 SPI D PWM1P22 PCM CLK CLK100 P23 PCM_DI SDA1 DP2 P10 ADC1 INTO P24 PCM_DO SCL1 PI INTI LE P25 PCM_FSC SF P12 INT2 SK P26 WTF_IN P13 INT3 SIO P27 BXTAL P16 PON P1ZICHARGE P3O PAOUTN DPO P31 PAOUTP DP1 P32 CIDINP MICHP P33 ADCO P35 RINGING RINGOUT RFO RF1 11 BDM1 3 3V vec Q eo Place near BDM1 1 8V 1C4 U1 VCC I o a near near near n Place Place Place o z o o z o VCCIO vec Place near BDM1 VCCPA Headphone Speaker Headphone Mic Bev B In cooporation with Bithium IST amp INESC ID Marcelo Uicente DECT Shield 28 08 2012 14 45 21
43. T CNICO LISBOA DECT Shield DECT Module Arduino Reset P N Micro SD NL Loudspeaker DECT Shield for Arduino Marcelo de Jesus Pardal Vicente Thesis to obtain the Master of Science Degree in Electrical and Computer Engineering Examination Committee Chairperson Prof Marcelino Bicho dos Santos Supervisor Prof Maria Helena da Costa Matos Sarmento Co supervisor Eng Ant nio Manuel Pedroso Muchaxo Member of the Committee Prof M rio Serafim dos Santos Nunes October 2012 ACKNOWLEDGEMENTS No work of this magnitude could have been done by a single individual in a short time without support That is why this work is not just mine but also of every person who helped me to achieve it and therefore they must be commended would like to thank Prof Helena Sarmento supervisor of the project for her constant availability to answer questions exchange ideas and for the scientific resources that greatly aided the development and writing of this thesis To Bithium want to show my deepest gratitude for their unquestionable support for letting me use their equipment and for having funded the necessary materials Without their support this thesis would never have been completed on time A special thanks to Eng Ant nio Muchaxo co supervisor for his suggestions criticism and guidance To Eng Alexandre Sousa a big thanks for the knowledge he shared and patience shown when helping me Finally thanks to Eng S rgi
44. T Shield layout rev A Jerri ie iania eiee Ena nemen rr nnns 26 Figure 3 14 DECT Shield assembled ee ee ee Re AA GR ee AR ee eene nnne nennen 27 Figure 3 15 DECT Shield layout rev B enm een ee ee ee rr 28 Figure 3 16 Software abstraction layers overview ee ee ee ee ee ee AR ee em emm eene 29 Figure 3 17 Protocol message ss ede ENE Ee vee eddie cr eie hagas De Re Ee dd dde Ge Se ee 30 Figure 3 18 Interface between abstraction layers ee ee RA GR ee AR ee Re emen 32 Figure 3 19 DECT API class declaratiON ees ees ee ee ee ee GR ee AR ee ee ee ee ee ee ee ee de ee ee ee ee ee 33 Figure 3 20 Terminal running on Arduino using PUTTY as interface iese ee ee ee ee ee ee ee ee 35 Figure 3 21 Telephone sketch state diagram sese emen 37 Figure 4 1 Bithium office Blueprint ie ee ee ee ee nemen ee de ee ee ee ee nnne nnns 39 Figure A 1 SPlsignalsin Mode 2 ierit a GE ee ke knee eene qo eis gee ee Ke dea 49 Figure B 1 DECT Shield schematic 1 of 2 ees ee ee ed RR ee E ee ee ee de ee ee emnes 52 Figure B 2 DECT Shield schematic 2 of 2 ees ieiet RR ee AR ee AAR ee de ee ennemis 53 Figure B 3 Bottom copper layer gd teens bie bee oe ee hee oe adiu ge 56 Figure B 4 Bottom solder mask iine tiara devs odia bir editus 56 Figure B 5 Top copper layer ecuacion uti eiu uidet latii diets 57 Figure B 6 Top solderimask ER EE dtc da pec addat 57 Figure B 7 Top silkscreemla
45. This shield has half the size of an Arduino Uno works at 3 3V and uses two VO pins The shield is equipped with a low cost generic Bluetooth module that can only work as a slave device with limited functionalities This module can communicate at 460 kbps up to 10 meters with Bluetooth master devices such as a computer USB dongle and does not support audio communication Wireless communication between shields is not possible but the software API compensates by being simple to use and understand Figure 2 5 Arduino wireless shields on the market a ITead Stackable Bluetooth Shield b Arduino XBee Shield All Zigbee shields available in the market use standalone XBee wireless modules from Digi 15 as seen in Figure 2 5 b The functionalities added to the Arduino depend on the XBee model attached to the shield Generally the shields are sold with a normal XBee which allows data communication up to 120 meters at 250 kbps More expensive versions come with an XBee Pro allowing the same data rates but up to 1 5km of distance Xbee modules support all standard Zigbee features but the communication API only allows to send data packets from point to point or from point to multipoint For additional features it is necessary to use AT commands The Zigbee network is automatically generated by the modules The official Arduino Wi Fi Shield 16 shown in Figure 2 5 c is one of the most complete wireless solution for Arduino This shield conta
46. Transmission Range The range tests were executed in doors and out doors In door tests were performed in the Bithium office depicted in Figure 4 1 and the out door tests in the countryside The transmission range depends on the BDM performance antenna and test conditions The BDMs used in the shields were an early revision and contain a problem related to the antenna diversity Therefore the tests might be influenced and show lower transmission ranges than the final version Figure 4 1 Bithium office Blueprint Kitchen Storage 1 The tests realized consisted in establishing several voice calls using the Telephone sketch and detect when the audio communication begins to show signs of interference or when one shield is unable to detect the other Tests in the Bithium office consisted in moving one shield to several locations inside the office and have the other shield stationary in TP1 The tests showed the shields are able to perform voice calls without interference at least 30 meters TP3 with no obstacles and up to 25 meters TP2 with obstacles The office dimensions limited the line of sight tests up to 30 meters in crowded DECT environments Therefore longer distances might be possible The only location in the office where the audio communication began showing signs of interference was in TP2 This room is covered with tiles and other construction materials that attenuate RF considerably so it was expected to have in
47. Y BDM Ready Signal 9 DSS BDM SPI Slave Selection 10 CSS microSD SPI Slave Selection 11 MOSI SPI Master Out Slave In 12 MISO SPI Master In Slave Out 13 CLK SPI Clock The SPI pins MOSI MISO and CLK can be shared with other shields for SPI communications Pins READY DSS and CSS cannot be shared because they are used to control the shield The shield can generate asynchronous events on the Arduino using the external interrupt pin INTO A buffer 31 is used in the shield to detach the signal from the Arduino when not in use allowing other shields to use this pin when the DECT Shield is not configured to generate events 3 3 6 CiRCUIT BOARDS The shield was first developed in a prototype board Figure 3 12 using a perforated board The prototype permitted to test all functionalities before investing in the final printed circuit board Figure 3 12 Prototype board The first revision of the PCB is designed after executing the tests in the prototype board that allowed the verification of all functionalities For the PCB design a freeware version of Eagle CAD 24 PCB 32 is used The design software includes a schematic editor a layout editor and a Design Rule Check DRC specification file from Eurocircuits 33 Some considerations 34 and recommendations are taken into account when designing the shield Use of 2 layers DECT antenna needs to avoid pin headers and cooper a
48. ackStoppedCallback Arguments pbstop Pointer to a callback function Return Nothing Description This function attaches a callback to the event triggered when the shield stops playing a file or sequence See example below for more information Code Example void pbstopCallback void Playback stopped TODO Add processing code here void setup lisis Set callback for when the playback stops dect attachPlaybackStoppedCallback pbstopCallback Remarks Event needs to be enabled using the SetConfigs function See the stEventsConfigs structure 89 Function attachPlaybackNextCallback Arguments pbstop Pointer to a callback function Return Nothing Description the next file in the sequence See example below for more information This function attaches a callback to the event triggered when the shield starts playing void void Code Example pbnextCallback uint8_t nNext Playback started playing the next file nNext Number of the current file playing TODO Add processing code here setup Set callback for when the playback goes to the next file dect attachPlaybackNextCallback pbnextCallback J ask Remarks structure Event needs to be enabled using the SetConfigs function See the stEventsConfigs 90
49. ality in a seamless way This channel allocation method permits DECT to adapt automatically to the environment conditions The DECT spectrum can be dynamically shared with other DECT applications and base stations without requiring prior channel allocation DECT uses the licensed 1 88 1 90 GHz spectrum therefore only DECT applications are allowed to use it DECT protocol architecture follows the lower layers of the OSI reference model 7 as illustrated in Figure 2 2 It has a physical layer OSI layer 1 a data link layer OSI layer 2 and a network layer OSI layer 3 The data link layer is formed by a medium access control layer MAC and a data link control layer DLC The DLC layer is separated in two planes the control plane is used for DECT signaling and interworking and the user plane for transferring user information e g voice and data The lower layer management entity LLME is used for all control activities Figure 2 2 DECT OSI Layers from 1 Control Plane User Plane Signaling Applicati Interworking ppications gt E fod E Network z OSI layer 3 7 layer ES DLC layer DLC layer E OSI layer 2 L MAC layer 5 z iS OSI layer 1 Physical layer The Physical layer PHY is responsible for specifying the radio parameters such as frequency timing transmission power bit and slot synchronization and for the transmitter and rec
50. ands are send to the EIL The EIL executes the commands and acknowledges to the Arduino by sending responses 31 Figure 3 18 Interface between abstraction layers HW SPI i Protocol External Interface Layer Data Command ENI RX i B stream Detection and amp Contents Verification and DECT Receiver buffer 9 verification of 9 execution of messages commands M j Audio ports Shield control TX Data Command functions stream i f amp Contents buic uc Generation o structures and P Events messages variables The EIL contains several structures to hold shield information which the Arduino can access and in some cases alter using commands The EIL has the following structures A configuration structure that contains the shield current settings regarding speaker volume microphone gain events etc Default configurations are applied when the shield is powered or after a reset A status structure that holds status information regarding the number of data packets available the number of pending events audio reproduction etc A FIFO structure to temporarily save received data packets from other shields The oldest data packet is sent to the Arduino when requested and is removed from the structure Incoming data packets are discarded when the FIFO is full A FIFO structure to hold pending even
51. annel supports frequencies up to 15 7 MHZ Finally the last maximum SPI clock frequency is calculated using 9 10 and 11 and is for when the DECT module is communicating with the microSD card In this case the clock signal coming from the BDM goes through one transceiver and the DO pin from the microSD through a single buffer 1 M SD e 14 7MH 9 cik 2 x 4 5ns 14ns 3 9ns 12 4ns d 9 trar tp 45ns 10 pmiso th 3 9ns 11 Although the module can output a clock frequency up to 20 MHz the channel only support a maximum of 14 7MHz which is better than using SPI emulation This clock frequency proved to be enough to read and write an audio file quickly with average bitrates 50 Appendix B PRODUCTION DOSSIER This appendix contains the Production Dossier which includes the information to produce and assemble the DECT Shield Rev B Firstly the circuit schematic is presented in section B 1 The drawings were made using the Light version of Eagle CAD 6 1 0 software from CadSoft 32 Secondly the Bill of Materials BOM is shown on Table B 1 of section B 2 Prices for the necessary components were gathered from Farnell Digikey and Mouser Finally on section B 3 the PCB layout artwork extracted from the Gerber files RS274X is presented 51 B 1 SCHEMATIC Figure B 1 DECT Shield schematic 1 of 2 J2 Place near SD Card 12A CSS Ko J 74ABT125DB 74ABT125DB DC
52. atible 53 playbackSize Changes the playback queue size 54 playbackQueue Queue a file from the memory card to the playlist if compatible Audio files can be opened using the playbackOpen or queued using the playbackQueue command The playbackPlay command begins reproducing the previously opened file or assembled queue The queue size needs to be set using playbackSize before issuing playbackQueue commands Table C 5 presents the commands to control audio components such as speaker volume and microphone gain 61 Table C 5 Commands of the Audio family ID Command Description 64 audioSpeaker Enable or disable the shield s speaker connection 65 audioLoudspeaker Enable or disable the shield s loudspeaker connection 66 audioVolume Hill the speaker loudspeaker volume from 2dB 0 to 12dB 7 in steps 67 audioMic Enable or disable the shield s microphone connection 68 audioGain Change the microphone gain from OdB 0 to 30dB 15 in steps of 2dB 69 audioConfig Returns the current audio configurations from the module Finally the last two commands present in Table C 6 permit the Arduino to control the microSD card The shield is not able to reproduce audio files when the Arduino has access to the card therefore a sdcardRelease command must be issued before executing any playback operation The shield is booted with the card relea
53. ble 3 5 List of commands supported by the Terminal sketCh se ee ee RR AR Re ee ee ee ee ee ee ee 35 Table 4 1 Measured average shield current consumption with a microSD card 42 Table 4 2 Shield cost estimation from BOM ee ee ee AR AR AE ee GR ee ee eene 42 Table A 1 Time constraints for each device in nanosecondsS ii se ee ee GR AR Ge ee ee ee ee ee ee 49 Table B 1 Bill of Materials GR RA Re ee ee ee Ge RA Re ee ee ee ee ee ee Ge ee ee ee ee Re Re ee ee ee ee ee ee nnns 54 Table B 2 Component prices from Farnell Digikey and Mouser seem 55 Table C 1 List of commands grouped in families ee ee ee ee Re ee RR ee Ge Re een 59 Table C 2 Commands of the Module family ese ee ee ee Re ee cano Re ee Ge Re eene 59 Table C 3 Commands of the DECT family ee se ee ee Ge Re Re ee ee Re ee RR ee ee Re ee ee Re ee ee ee 60 Table C 4 Commands of the Playback family ees ee se ee RR ee Re ee ee Re ee Ge ee ee Re ee ee ran 61 Table C 5 Commands of the Audio family ee se seems 62 Table C 6 Commands of the microSD family ee ee Re RR nennen eene 62 LIST OF ACRONYMS ADPCM AES API BDM BOM DCS DSC DECT DIY DLC DRC DSP EIL ENI FDMA FP GCC GMSK 12C ISP IWU LED LLME LMP MAC MC NWK PCB PCM PHY PSTN PP RF SIM SPI SOHO RFPI Adaptive Differential Pulse Code Modulation Advanced Encryption Standard Application programming interface
54. ble Parts can be scanned Function GetInfo Arguments None Return stInfo structure with the current DECT Identifier Description This function returns the DECT RFPI if working as fixed part or IPUI if as portable part Code Example void loop J ass Get shield IPUI and print it stInfo sInfo dect GetInfo Serial println sInfo nIPUI DEC Js spes Function GetPincode Arguments None Return stPincode structure with the current pincode discriminated Description This function returns a structure with the shield current pincode Remarks If the values of fields n5 through n8 in stPincode are OxOF then the pincode has only 4 digits Function SetPincode Arguments pPinCode stPincode structure with the new pincode to be applied to the shield 1 Arguments n1 First digit of the pincode from 0 to 9 2 n2 Second digit of the pincode from 0 to 9 n3 Third digit of the pincode from 0 to 9 n4 Fourth digit of the pincode from 0 to 9 Arguments n1 First digit of the pincode from 0 to 9 3 n2 Second digit of the pincode from 0 to 9 n3 Third digit of the pincode from O to 9 n4 Fourth digit of the pincode from 0 to 9 n5 Fifth digit of the pincode from 0 to 9 n6 Sixth digit of the pincode from 0 to 9 n7 Seventh digit of the pincode from 0 to 9 n8 Eighth digit of the pincode from O to 9 Return Nothing Descrip
55. by the ENI and support for more audio codecs can be increased Reducing the programming space in the Arduino API is a point to be improved since it is occupying more than anticipated Different programming models can be implemented and tested to obtain better results Finally additional tests using more than two devices need to be performed 45 REFERENCES 1 ETS 300 175 Radio Equipment and Systems RES Digital Enhanced Cordless Telecommunications DECT Parts 1 5 ETSI 1992 2 University of Manchester DECT 2005 Online Available http www cs manchester ac uk ugt COMP38512 cs3091_docs TELE DECT html Accessed September 2012 3 A Schuler E Tews and R P Weinmann deDECTed org in 25th Chaos Communication Congress 25C3 Berlin Germany 2008 4 Hack n Mod Top 40 Arduino Projects of the Web Online Available http nacknmod com hack top 40 arduino projects of the web Accessed September 2012 5 A Muchaxo A Sousa N Pereira and H Sarmento Wireless Data Communications Using DECT Air Interface ACM SIGCOMM Computer Communication Review vol 29 April 1999 6 H Eriksson Performance of dynamic channel allocation in the DECT system Vehicular Technology Conference 1991 Gateway to the Future Technology in Motion 41st IEEE pp 693 698 May 1991 7 Standard ISO IEC 7498 1 Information technology Open Systems Interconnection Basic Reference Model The Basic Model
56. can be configured as push pull or open collector Push pull allows for faster transition rates but operate at 1 8V which is not supported by the microSD and the Arduino as both require input signals of at least 2 0 V and 3 0 V respectively An external logic level translator can be used to boost the output voltage Ports configured as open collector can operate up to 3 5 V and require a pull up resistor Signal transition speed and port current consumption is affected by the resistance of the pull up 25 Ports in open collector can be connected to the Arduino and the microSD since the output voltage is inside the detection range The maximum voltage of BDM input pins is 3 5 V Therefore the inputs can be connected directly to the microSD card outputs which operate at 3 3V Arduino outputs operate at 5V and are reduced using logic translators and resistor dividers 15 Transition times of signals required to control the SPI circuitry are not critical Therefore it was decided to use open collector configuration SPI interface ports are configured as push pull because data rates can become affected by the slower transition times The SPI signals are converted using logic translators instead The pull ups have a resistance of 4 7 kO The average current consumption per pull up when the output is at low level is 0 7 mA at 3 3V Higher resistor values would reduce current consumption but increase transition times 3 3 2 SPI INTERFACE
57. cation example mimics Text to speech in the Arduino by using the DECT Shield to play audio files from the memory card exemplifying file reproduction and shield configuration The Text to speech sketch receives a sentence from the serial port and identifies the different words For each word an audio file is played by the shield if it exists Audio files associated to words 36 are stored in a microSD card and are organized in two level folders to reduce search time For example the audio file for the hello word has the following path n e llo wav The Arduino converts each word into a file path and commands the shield to open and play the target file The audio files used for testing purposes were obtained from the AT amp T Natural Voices 39 website which allows inputting text and downloading the corresponding audio file Each file downloaded is in PCM 16 bit 16 kHz WAV format and was converted to p Law 8 bit 8 kHz WAV format which is compatible with the shield 3 5 3 TELEPHONE Telephone is a test sketch that emulates a rudimentary telephone between two DECT Shields one working as portable part and another as a fixed part The sketch permits to test events voice communication data transfer and shield configuration The application implements a contact list ringing conversation and hang up Interaction with the sketch is performed through the serial port Figure 3 21 illustrates the sketch state diagram
58. croSD card are the slowest and can take up to 3 seconds of execution Commands that control audio are executed in less than 1 ms since they do not require access to the ENI DECT commands can take up to 125 ms for data and voice communication and up to 5 seconds for registration operations Finally configuration commands generally take up to 50 ms The times presented are after the BDM starts executing the command Programming Space The DECT API library for the Arduino requires approximately 4 kB of programming space and 12 bytes of RAM The API occupies approximately 12 of the programming space available in an Arduino Uno leaving 28 kB free for user code or other libraries The combined firmware for the BDM PP and FP occupies approximately 220 kB and consumes half the RAM available to hold data structures 41 Shield Consumption Table 4 1 presents the average measured current consumption of the shield using an ampere meter The measurements are within expected values Table 3 2 and no irregularities were detected Table 4 1 Measured average shield current consumption with a microSD card Mode of operation Portable part mA Fixed part mA Idle 9 5 21 0 Voice communication w o loudspeaker 24 0 33 5 Voice communication w loudspeaker 55 5 64 0 Data transmission 19 5 31 0 File reproduction w o loudspeaker N A 24 5 The shield consumes less when working as a portable part because the DS
59. ction GetCallList Arguments pList Pointer to a pre allocated vector of stCallElem structures nElements Number of elements in the pList vector Return Returns the number of elements written in the vector Description This function fills the pList vector with the list of all call channels and their correspondent state The call identifiers can also be used In the Call function to handle ongoing calls Code Example Note Function void loop L aa uint8 t i j stCallElem sList 8 p is a serial printf i dect GetCallList sList 8 if dect LastError Print header p P PSTR Index Link Out State n r if i 0 p P PSTR No calls to inform n r else Print call state ter j j lt i j 1 p d d s j sList j nLink sList j bOutgoing Yes No if sList j eState NoCall Serial print No Call else if sList j eState PendingCall Serial print Pending else if sList j eState OngoingCall Serial print Ongoing else if sList j eState RefusedCall Serial print Refused else if sList j eState TerminatedCall Serial print Terminated by user else if sList j eState destination else if sList j eState else if sList j eState else Serial println Failed IT wes DestinationEndedCall Serial print Terminated by DisconnectedCall Serial print Disconnected InvalidCall Serial print Invalid
60. ctional communication between the Arduino and the shield e Easy to use Arduino API for shield interface e Support for asynchronous events e Shield dimensions similar to an Arduino Uno The final solution has to consist of an Arduino library which can be used in sketches a custom firmware for the BDM which supports all features and at least two fully assembled shields for testing 3 2 DECT SHIELD Some decisions and considerations are taken into account using the requirements defined previously in order to design the DECT Shield hardware and software This section provides an overview of the components that constitute the shield including some of the decisions involved in the design and planning procedure A detailed description is provided in the next sections It was decided to place the BDM responsible for the shield control and the DECT communication handling allowing the Arduino to execute other tasks in parallel The BDM is significantly more powerful than the Arduino due to a superior CPU architecture clock frequency and memory available 12 For that reason this approach is efficient reducing significantly the code size of the Arduino sketches and the number of VO pins necessary to connect the shield to the Arduino To control the shield a command based message protocol is specified and implemented The Arduino is able to send commands to the BDM containing instructions and the BDM can interpret them e g make call
61. cultadores colunas e microfone Os testes realizados mostram que os shields permitem usar correctamente a maioria das funcionalidades suportadas pelo DECT A comunicac o com o Arduino usando SPI mostrou ser bastante toler vel a erros e fi vel uma vez que raro perder mensagens quando o canal SPI est congestionado O alcance e velocidade das comunicag es de som e dados ficaram dentro dos par metros normais do DECT A API desenvolvida resultou num conjunto de fun es muito f ceis de usar e perceber em comparac o com outras APIs de shields existentes A principal aplicac o desenvolvida consiste num sistema de telefone sem fios com comunicac o de udio e dados abrangendo a maioria das funcionalidades disponibilizados pelo shield PALAVRAS CHAVE DECT Comunicac o sem fios Arduino Transmiss o de som SPI Cart o microSD Circuito Impresso CONTENTS Acknowledgements EE trend et bigis e uro OE EE N ii ADStIacti cena ete REGI OE A eel EE OE AE iv BERE EE EE EE OE EE EE EE N V Contents inen dub Eodem uu eA vi Listof EIg res i 5 ose ER ies Tt am boni te dus hse ATOAN viii Ee ME le e X EiSt Of ACTODVITIS AE Rc nete dre ta EE EP diit KERE decet et eee xi A A epit ad dep de dee eue Atl eel ld e ee eine 1 2 Technologies and Applications iis ee ee ER AR AE EE GR RA Re ee ee eese ener erret ee ee ee ee ee 3 2 DECIA ie to DER o el ales aec bo etae foa 3 PSP AMEN eb ER
62. d Ee td nde ott edt detti A 44 Masse ERE 46 Appendix A SPETiming Analysis x dime Ein aida 48 Appendix B Prod ction Dossler 2 rrt i A de eed ada dg e da e 51 Bil Schematic RE EE EE EE RE OE OE IE 52 B 2 Bill ot Materlals Es ue ee cli tebe nied dea ED EG N Ee RE tact 54 B 3 Layout A t rd ese EE te iuste T 56 Appendix C External Interface layer ei rear e d deg deb edt 59 Appendix D BEGT API 35 irte a ebbe N cr 63 BE ae RE RE OE NE a ME aul ce d OO de ed ee e e etd 63 D 2 Library Usage ten teer tton ded etia n Eid enn Eas 63 D 3 Module Group FUNCtIONS ocococononocicnnncccinnonconccnnnnnnnnnnononncnnnnnnnnn nono reete en ee nene Re ee sn ee nennen nnns 68 D4 DECT Group E hctloris ecrire tata 75 DS Playback Group FUNGUOM sets EED a ultra oa 82 D 6 Audio Group Functions iS ri e eere deities el nee ER Ee euge e deg egens Eg Ue ee De Ee Ee id 84 D 7 MicroSD Group FunctiOnS iese ee ee ek RA ee a ee ee eene emere enn nennen nnne nnne nnns 86 D 8 EventGtoup FUNCION EE EE ES SE Ge Se e HER RR ERR RR AD IRURE 87 vii LisT OF FIGURES Figure 2 1 DECT star topology one tin rd Hem Ee Ee aet re YER EC ed De E ER 3 Figure 2 2 DECT OSI Layers from h urnana e ee ee Re ee ee Re ee ek Re ee eke ene AAE 4 Figure 2 3 DEC T frame from Devi rt e e e EO Fe ee REDE P Ee lecti b anaes 5 Figure 2 4 Arduino Uno mined R aped mda tes 7 Figure 2 5 Arduino wireless shields on the market ees ee ee ee e
63. d to the Bluetooth Shield which supports rates up to 460 8 kbps and the XBee Shield supporting rates up to 250 kbps the DECT Shield comes as an inferior solution but with native voice support The data rates can be improved by adding support for dedicated data channels in a future firmware DECT Communication Handling Several tests were performed to verify if the shields were handling DECT voice communication calls correctly The tests consisted in establishing a voice call and then terminate or refuse by ending the call normally turning off one of the shields or get out of range The results showed some inconsistencies which were corrected when a call was lost Data communications did not show any errors since the shield only recognizes an incoming package when it is received without errors SPI Communications Tests were executed to detect errors in the SPI channel Communication between the Arduino and the BDM is performed at 1 MHz and at 10 MHz between the microSD card and the BDM respectively Tests showed that the shield firmware controls the SPI circuitry correctly and no software lockouts were detected during stress tests 40 A stress test was performed by sending several commands in sequence to the shield when reproducing a file This test showed that the Arduino received all commands correctly and no audio gaps were detected at these frequencies Additionally a test was created to generate invalid protocol message
64. e shield DECT Handle registration data and voice communication between shields Playback Control and configure audio file reproduction from the microSD card Audio Configure the speaker loudspeaker and the microphone connections Memory Card Control the microSD card access privileges There are some commands such as dpc for the pin code and dreg for the registration procedure which can be used to different purposes based on the arguments For instance if dreg is called without arguments then the current pin is returned otherwise it will be change Table 3 5 List of commands supported by the Terminal sketch Command T Group ame Semina Arguments Returns Description Version mv Version Gets the current version Firmware mf PP FP Changes the firmware type Reset mr Resets the module Module Defaults md Reset with the default settings Status ms Status Requests all status information Configure mc Configs OK Fail Configure the module Event me Event Request last pending event 35 Table 4 2 continuation List of commands supported by the Terminal sketch Info di RFPI IPUI Return RFPI FP or IPUI PP Pin Code dpc Pin e Set or get the pincode List Modules dl us Get the list of registered modules Send Data ds Pin Ok Fail Send data to another module Receive Data
65. ePath bool SetPlaybackQueue uint8 t nSize bool QueueFile const char pFilePath The description of each structure and function present in this group follows Function StartPlaying Arguments None Return Nothing Description This function plays a previously opened file or a sequence of files in the module speaker and loudspeaker if enabled Remarks An audio file must be opened with OpenFile first Function StopPlaying Arguments None Return Nothing Description If there is a file playing this function will sever the audio stream and stop the playback 82 Function SetPlayVolume Arguments nVolume Playback volume Return Nothing Description This function changes the file playback volume not the speaker from O muted to 15 maximum Code Example void loop J sss Set the playback volume to the maximum value dect SetPlayVolume 15 LH ues Function GetPlaybackStatus Arguments None Return stPlaybackStatus structure with the current playback status Description This function returns the shield s playback status This information can also be obtained using the GetStatus function Code Example void loop Td iss Get shield playback status stPlaybackStatus sStatus dect GetPlaybackStatus Verifies if the previously opened file is valid if sStatus bValid true
66. eiver performance It uses TDMA Time Division Multiple Access TDD Time Division Duplex and FDMA Frequency Division Multiple Access The DECT spectrum is split into 10 frequencies of operation allowing multiple carriers MC Due to the use of FDMA each channel will use one of ten frequencies available DECT employs 10ms frames each with 24 slots TDMA as shown in Figure 2 3 The slots are separated into two groups of 12 slots one group for the uplink PP to FP and the other for downlink FP to PP A duplex DECT channel is a combination of one uplink and one downlink slot through the use of TDD DECT supports up to 120 duplex channels as result of 10 different frequencies and 12 duplex channels per frequency Figure 2 3 DECT frame from 2 1 DECT Frame 24 Time Slots 12 each way 10ms 3 320 bits B field 4 parity bits Time slots are formed by a 32 bit preamble marking the beginning of a slot a 388 bit payload which contains DECT control and user information and a 60 guarding bits to prevent slot collisions The MAC layer specifies how logical channels are mapped and multiplexed to the physical channels It provides channels for signaling information to the control plane These channels are mapped to the A field in the payload which has 64 bits The B field consists of 320 bits where user information is placed resulting in a normal bit rate of 32 kbps because the slots are transmitted every 10ms This fi
67. eld is mainly used to send voice over the air in ADPCM format and is not suitable for data because there are only four parity bits for error checking For data transmission the 320bits in B field are organized into four 80bits blocks with 16bits for error correction protected B field Using protected B field reduces data rate to 25 6 kbps In order to obtain higher transfer speeds it is possible to group multiple sequential slots The DLC layer delivers services for the control and user plane The control plane provides a point to point service and a broadcast service taking care of addressing frame delimiting error control flow control segmentation and fragmentation of frames and connection handover The user plane provides frame relaying frame switching and rate adaptation services The DLC layer requires two bytes for data transfer when using protected B field reducing the data rate to 24 kbps DECT control frames can also be used to transmit data up to 1 2 kbps Table 2 2 presents some characteristics of DECT ZigBee Bluetooth Wi Fi and GSM GPRS DECT advantages over other commercially available wireless technologies are low power consumption short medium communication distance reliable voice communication but provides smaller data rates DECT is the only standard which provides short range voice communication natively Table 2 2 Characteristics of different wireless technologi
68. em eState Pending if sListElem eState Ongoing Serial println Call was accepted else Serial println Call was refused LE sis 67 D 3 MODULE GROUP FUNCTIONS This group includes the following functions e enum DECTError LastError void e stVersion Version void e void Reset void e void Defaults void e bool GetConfigs stConfigs pConfigs e bool SetConfigs stConfigs pConfigs e stStatus GetStatus void The description of each structure and function present in this group follows Structure enum DECTError Description Represent an error with the shield communication enum DECTError NoError 0 No error occurred InvalidCommand Invalid command ID InvalidChecksum Checksum mismatch InvalidTermination Message termination problem Timeout Timeout BufferTooSmall Given buffer doesn t have enough space ReadyNotDeasserted SPI CS not deasserted ReadyNotAsserted SPI CS not asserted Structure struct stVersion Description Shield version structure typedef struct uint8_t nMinor 5 Minor Version uint8_t nMajor 2 Major Version uint8 t nFirmType 1 Firmware Type stVersion Remarks nFirmType filed is O for Fixed Part firmware or 1 for Portable Part Structure struct stConfigs Description Configuration structure for every component in the shield typedef struct stEventC
69. en shields is represented in Figure 3 2 The figure also illustrates how the software libraries described interact with each other providing an overview of the software components present in the Arduino and the BDM Figure 3 2 Data communication between two DECT shields Arduino A DECT Shield A 2 DECT Shield B Arduino B a 1 Y z User 5 zalzlz DECT DECT slalz D lz lt User Code 2 aw Stack Stack sd els al Code E 3 1 A sequence of operations consists of the following 1 Arduino A sends a message containing a command and a payload requesting DECT data transmission 2 The BDM on the transmitter shield A sends the payload through the air to the receiver shield B 3 If the payload was successfully sent the transmitter shield A responds by acknowledging the Arduino otherwise it responds indicating a failure 4 An event is sent by the receiver shield B to inform its Arduino B that a new payload has arrived and is available for reading 5 Arduino B at the receiver part acknowledges the event by sending a message to the shield B requesting the payload which was received 6 The receiver shield B acknowledges the received command and transfers the payload to the Arduino B 14 3 3 HARDWARE This section provides a detailed description of the hardware components and how they
70. erate as master and slave at the same time using a single SPI interface Figure 3 4 illustrates the distinctions between the two modes Figure 3 4 SPI communications channels in Mode A and Mode B Arduino Arduino Master Slave Master Bithium DECT Bithium DECT microSD microSD Slave Module Slave Module Master Slave EE EN DECT Shield SPI Mode A Shield isolated SPI Mode B Shield connected to the Arduino Mode A allows the BDM to read files from the microSD card and the Arduino to communicate with other shields In this mode the SPI bus connecting the shield to the Arduino is in tri state which allows communication with other shields without interference from the DECT Shield The BDM operates as master in order to access the microSD card 17 Mode B allows the Arduino to access the BDM and the microSD card The Arduino operates as master and other shields cannot use the SPI bus The BDM is in slave operation in order to receive data from the Arduino and cannot access the microSD card Figure 3 5 illustrates the schematics diagram of the circuit that shares the SPI bus between the Arduino BDM and the microSD card DSS and CSS are the SPI selection pins for the BDM and the microSD card respectively Figure 3 5 SPI tri state buffer schematics diagram Shield tri state isolation in Mode A is achieved using four buffers
71. es extracted from 1 8 Feature DECT ZigBee Bluetooth Wi Fi GSM GPRS Topology Star Mesh Tree Star Star Star Tree 868 915MHz 2 4GHz 800MHz Spectrum 1 9GHz 2 4GHz 2 4GHz 5 8GHz 4 9GHz Pin code Pin code Security DSC AES 128bit LMP WEP WPA SIM 64bit e 32 kbps 250 kbps 723 kbps 105 Mbps 114 Kbps Range max 300 m 1 5 km 100 m 100 m N A Power Very LOW Very Low Low High High 2 2 ARDUINO Arduino 9 is an open source electronics prototyping platform base on flexible easy to use hardware and software It is intended for artists designers hobbyists and anyone interested in creating interactive objects or environments There are twenty different official prototype boards fully supported and documented by the Arduino development team The open source hardware consists of an 8 bit Atmel megaAVR processor 10 with on board input and output interfaces The software consists of a simple IDE with C C support to write sketches and a custom GCC compiler The Arduino processor has a boot loader which is used to transfer new sketches an Arduino program through an USB or RS 232 interface The Arduino IDE is a multiplatform program developed in Java which is used to write compile and deploy sketches to the Arduino The IDE comes with several C C libraries imported from the Wiring 11 project providing a set of base functions targeted for hardware sensing and controlling Arduino boards follow the same layout and specificat
72. et information about the BDM such as the firmware version and the configurations Table C 2 Commands of the Module family ID Command Description Ol moduleVersi n Returns the current firmware running in the module as well its current version in the following format FP FP Major Revision Minor Revision 1 moduleFirmware Changes the module firmware to Fixed Part or Portable Part 2 moduleReset Performs a software reset of the module 3 moduleDefaults Same as moduleReset but default settings are also applied during reset 4 moduleStatus Returns the module current status information this also includes status for the DECT Playback and Audio 5 moduleConfig Returns or sets the module configurations based on the arguments These also include the DECT and Audio configurations 6 moduleEvent Returns the oldest pending event if available from the module 59 DECT commands are presented in Table C 3 Some commands have dual functionality depending on the BDM firmware The dectScan and dectScanlist commands which are used to scan for Fixed Parts are only accepted by Portable Parts Table C 3 Commands of the DECT family ID Command Description Fixed Part Returns the module s DECT RFPI 16 dectinfo Portable Part Returns the module s DECT IPUI 17 dectPincode Change or returns the module s DECT current pin code 18
73. he associated command and invalid messages are discarded 3 4 3 AUDIO PLAYBACK The microSD layer and the FAT32 layer Figure 3 16 are used to allow audio reproduction from files stored in the memory card The microSD layer defines the interface between the microSD card using SPI and the FAT32 layer implements a FAT32 file system to open the contents stored in the card 30 The microSD interface layer based on the SanDisk Secure Digital Card specifications 35 includes the functions to initialize read write data block and to address the card through SPI The card initialization procedure contains a problem related to the BDM SPI interface which the minimum clock frequency is of 741 kHz Initialization must be executed at a maximum of 400 kHz which is almost double of the minimum clock frequency supported by the BDM A workaround is implemented to solve this problem by adding delays and repetitive attempts until the card is successfully initialized After initialization which can take up to 3 seconds the clock frequency is changed to 10 MHz increasing the data rate considerably The FAT32 layer is a generic FAT32 file system emulator which in this case is interfaced with microSD cards The implementation is based on the Microsoft FAT32 specification 36 and supports all FAT32 features including long names and long directory entries The developed function set for the FAT32 layer allows navigation through directories file inspection
74. he following functions e void AccessmicroSD void e void ReleasemicroSD void The description of each structure and function present in this group follows Function AccessmicroSD Arguments None Return Nothing Description This function enables to Arduino to access the shield s microSD slot Remarks Other shields can t use the SPI while the shield is granting access to the Arduino 86 Function ReleasemicroSD Arguments None Return Nothing Description This function releases the microSD card from Arduino control This function should always be called when the Arduino doesn t need to access the card anymore Remarks Other shields can use the SPI bus after calling this function D 8 EVENT GROUP FUNCTION This group includes the following functions e bool GetEvent stEvent pEvent e void attachRecvCallback void recv uint8 t uint8 t uint8 t e void attachCallCallback void call uint8 t enum CallState enum CallState e void attachPlaybackStoppedCallback void pbstop void e void attachPlaybackCallback void pbnext uint8 t In order to enable events it is necessary to configure the shield using the SetConfigs function as exemplified in Figure D 7 Figure D 7 Event configuration code void setup SEC stConfigs sConfigs dect GetConfigs amp sConfigs Enable Data Events sConfigs sEvents bDataEvent
75. ield 2 as Portable Part as Fixed Part dectScan dectRegister A Registration Scanning Enabled Enabled OK OK dectScanlist Get detected Fixed Parts Becon 34 List XX xx xx xx xx Beacon is being broadcast Time dectRegister I Pincode Request detected Request registration A accept it OK Accepted dectList dectList Get part Identifier Get part Identifier List bo N 7 bo List After registration there is an identifier associated to the target shield which can be obtained using the dectList command dectRecv dectSend and dectCall can use the identifiers to reference a shield Identifier O represents all registered parts and can be used to send a data packet to every registered module for example The commands to control audio file reproduction in the shield are listed in Table C 4 Audio playback is restricted to shields working as fixed parts and playback commands sent to portable parts are rejected Table C 4 Commands of the Playback family ID Command Description 48 playbackPlay Plays a previously opened WAV file or a sequence of files 49 playbackStop Stops playing the current file if any 50 playbackVolume Changes the playback volume directly in the DSP from 0 to 15 51 playbackStatus Returns the current playback status information from the module 52 playbackOpen Open a file from the memory card if comp
76. ime it takes for the slave to update the data out bit needs to be taken into consideration t 4 This new bit needs to reach the master and also takes additional time tomiso The bit path might be formed by some buffers and possibly a transceiver so the formula for tycu is the same for tomiso There is also a setup time associated to the data in line the new bit needs to be detected by the master at least tsetup before a falling edge The final formula to calculate the maximum SPI clock is given by 2 f 1 1 1 k EE E teik 2 tmin 2x tye t do tomiso oup The time necessary for the MOSI signal to go from the master to the slave is not taken into account because it normally takes more time than tpax but less than tmin tsetup In all three possible SPI communication channels this condition is true and it does not affect the clock speed Table A 1 shows the timings for each IC present in the shield and Figure A 1 illustrates the SPI protocol in Mode 2 In this mode the input bits are sampled on the clock falling edges and are updated on the rising edges The Arduino BDM and microSD use Mode 2 for communication 48 Table A 1 Time constraints for each device in nanoseconds Time A auno Bithium DECT Module microSD 22 SN74LVTH125 SN74AVC4T245 Master Slave 26 27 tado 10ns 5ns 12 5ns 14ns tsetup 10ns 12 4ns 5ns 6ns ty 3 9ns 4 5ns Figure A 1
77. ins an integrated Wi Fi module and a 32 bit Atmega 32UC3 working as a co processor for controlling The 32UC3 firmware runs a TCP IP stack and allows TCP and UDP connections over Wi Fi by using the module This shield is open source and the API covers every aspect related to Wi Fi allowing encryption and supports client server applications for example An Arduino shield for GSM GPRS communications also exists 17 and is present in Figure 2 5 d A SIM900 18 module from Micron Electronics is used for GSM and GPRS related operations 8 The shield allows to establish TCP connections and to make and accept calls using GSM For audio interface the shield has on board connectors for a headset The API used is very complete covering all functionalities supported by the module The shield contains some of the features included in the Wi Fi shield API such as a TCP IP stack Table 2 3 presents a summary of the characteristics and features of the shields described It is possible to see that the cost of each shield depends greatly on technology functionalities and range The DECT shield has to be a low cost solution similar to the XBee Shield has to have low power consumption medium transmission range and an API which is able to provide an interface with most DECT functionalities when compared to the other shields Table 2 3 Wireless shields characteristics and features Shield Cost average Functionalities API
78. ions regarding pin placement to allow the connection of daughter boards or shields without incompatibility issues The Arduino shields are stackable hardware boards that connect to the Arduino using the pin headers and extend its functionalities Nowadays there are more than 250 available shields in the market 12 The boards used in this thesis are Arduino Uno prototype boards 13 Figure 2 4 with a USB connection a DC power jack and twenty I O ports for connectivity Some of these I O ports have multiple functionalities such as UART SPI I2C or PWM The processor is an 8 bit Atmel Atmega328 working at 16 MHz It has 32 kB of flash programming space in which 512 bytes are reserved for the boot loader 2 kB of RAM and 1 kB of EEPROM The boards have an on board 5 V regulator for the 1 Depends on the infrastructure e g cell towers repeaters DECT Ultra Low Power ULP processor and l O ports and a 3 3 V regulator for the USB interface Both regulators can be accessed using pin headers Figure 2 4 Arduino Uno EN ANALOG IN a enanme nl 2 3 ARDUINO WIRELESS SHIELDS There are shields in the market that already add wireless functionalities to the Arduino from Bluetooth to GSM This section presents an overview of some of these shields in order to compare their advantages and disadvantages The most popular Bluetooth shield for the Arduino is the ITead Stackable Bluetooth Shield 14 as depicted in Figure 2 5 a
79. k ke ee ek Re ee ek ke ek ke eee 8 Figure 2 6 BDM layout and dimensions ee ee ee ee ek ke ee ek Re ee ee Re ee erties ee ee be ee ee ek ke ee ee be ee ee ke ee 9 Figure 2 7 BDM typical communication ee ee ee ee Re AA GR ee AR ee eem nennen mme 10 Figure 3 1 DECT Shield architecture ees ee ee ee ek ee GR ee ee ee ee eem ee ee ee ee ee ee ee ee ee ee ee 13 Figure 3 2 Data communication between two DECT shields eie ees ee ee ee ee AR ee AR ee ee nc 14 Figure 3 3 SPI communication channels between the Arduino BDM and microSD card 17 Figure 3 4 SPI communications channels in Mode A and Mode B ee ee ee ee AR ee AR ee ee 17 Figure 3 5 SPI tri state buffer schematics diagram sse 18 Figure 3 6 SPI buffers in Mode A BDM connected to microSD iese se ee ee ee ee AA Ge ee ee ee ee 19 Figure 3 7 SPI buffers in Mode B Arduino connected to BDM iese see ee ee ee AA Ge ee ee ee ee 19 Figure 3 8 SPI buffers in Mode A Arduino connected to microSD i ie se ee ee ee ER RR Ge ee ee ee 20 Figure 3 9 BDM to speaker connectionS ee ee ee ee ee ee GR ee eene ee ee ee Re ee ee ee ee ee ee 21 Figure 3 10 Microphone to BDM connectionS ee ee ee ee Re ee ER Re AR ee em emere 22 Figure 3 11 BDM to loudspeaker connections ie ee ee Re AA ER Re AA AR AA GR ee ee ee nemen 22 Eigure 3 12 Prototype board si erede mdb eie er dee ted dm 24 Figure 3 13 DEC
80. ker configurations stAudioMic sMic Microphone configurations stAudioConfigs Remarks The structures forming stAudioConfigs are described below 69 Structure struct stAudioSpeaker Description Speaker and loudspeaker configuration structure typedef struct uint8 t nVolume uint8 t res uint8 t bLoudspeakerEnabled uint8 t bEnabled Loud Speaker volume Reserved Loudspeaker Enabled Speaker Enabled e HU Uu stAudioSpeaker Remarks Present in stAudioConfigs Speaker volume goes from 0 2dB to 7 12dB in steps of 2dB Structure struct stAudioMic Description Microphone configuration structure typedef struct uint8 t nGain 4 Microphone Gain uint8 t res 3 Reserved uint8 t bEnabled 1 Microphone Enabled stAudioMic Remarks Present in stAudioConfigs Microphone gain goes from 0 0dB to 15 30dB in steps of 2dB Structure struct stStatus Description Shield status structure typedef struct stEventStatus sEvents Event Status stCallStatus sCalls Call Status stDataStatus sData Data Status stPlaybackStatus sPlayback Playback Status stStatus Remarks The structures forming stStatus are described below Structure struct stEventStatus Description Event status structure typedef struct uint8 t nCo
81. mission SPI Micro SD card PCB RESUMO A plataforma de desenvolvimento de hardware open source Arduino tem vindo a crescer nos ltimos anos Devido a este crescimento tem surgido uma vasta variedade de placas de expans o shields com as mais diversas finalidades desde simples expans es l gicas at inclus o de suporte Ethernet Desde 2011 existem shields para comunicac o sem fios usando ZigBee WiFi e GSM mas ainda n o existe nenhum com DECT Digital Enhanced Cordless Telecommunications A principal vantagem da tecnologia DECT face s outras j mencionadas permitir transferir som com elevada fiabilidade at 100 metros sem necessidade de infra estruturas ou elevado processamento adicional e g GSM Esta tese descreve a conceptualizac o o desenvolvimento e o teste de um shield para o Arduino equipado com tecnologia DECT que permite transmitir som e dados para outros shields semelhantes ou para dispositivos equipados com DECT tamb m desenvolvida uma API Application Programming Interface em C para ser usada com o IDE Integrated Development Environment do Arduino a fim de fazer a interface com o shield usando SPI Serial Peripheral Interface Esta API permite usar dois modelos de programa o distintos por polling de eventos ou por interrupc es O shield tamb m contem um cart o de mem ria microSD que pode ser usado para armazenar ficheiros de som a fim de serem reproduzidos e sa das de udio para ligar aus
82. n enum CallAction MakeCall 0 Make a new call AcceptCall Accept an incoming call RefuseCall 2 Refuse call TerminateCall 2 Same as RefuseCall Remarks Used exclusively with the Ca11 function Structure struct stCallElem Description Element from a list of calls typedef struct enum CallState eState 3 State of the call uint8 t bOutgoing uint8 t nLink stCallElem 1 Call is outgoing 4 Link number associated with the call Remarks The CallState enumerator is described below Structure enum CallState Description Enumerator used to indicate a state of a call enum CallState NoCall 0 No call as yet been made PendingCall Current call is pending OngoingCall Call undergoing RefusedCall Call was refused TerminatedCall Call was terminated by user DestinationEndedCall Call was terminated by destination DisconnectedCall Call was disconnect for some reason InvalidCall Call wasn t allowed to go through 3 Remarks Used in the list of calls to indicate the state of each call 76 Structure struct stScanElem Description Element from a list of scanned parts typedef struct uint8 t nRSSI Radio Signal Strength Indicator uint8 t nRFPI 5 Radio Fixed Part Identifier stScanElem Remarks There is no IPUI since no Porta
83. n order to implement the SPI circuitry the buffers need to be e Activate low Buffers are disconnected when the shield is powered on e 5V tolerant inputs Arduino outputs can be directly connected to the buffers e Low propagation delay lt 5 ns Preserves SPI data rates The propagation delay is recommended to be lower than 1096 of the minimum SPI period of the BDM which is 50 ns 5 ns does not affect the signal propagation significantly The buffers used in the shield 26 comply with the requirements and have a propagation delay of 3 9 ns when operating at 3 3 V The pull ups in the control lines force the activation signals to be high when the shield is powered The logic transceiver to boost the voltage level of the BDM SPI outputs has the following requirements e Bidirectional For the SCK and CSS signal which operate as input and output e Low propagation delay lt 5 ns Preserves SPI data rates e 1 8Vto 3 3 V conversions The transceiver used in the shield 27 meets the requirements and has a maximum input output propagation delay of 4 5 ns when operating from 1 8 V to 3 3 V Some tests were executed to boost the signals using a single MOSFET and two pull ups 28 per signal instead of a transceiver Although the results were acceptable the necessary MOSFETSs to work at 1 8 V were much expensive than using a single transceiver IC Appendix A contains the SPI timing analyses performed to determine the best SPI clock
84. nologies require e g GSM This thesis describes the conceptualization development and testing of a DECT shield for Arduino that allows audio and data transmission to other DECT shields or to other DECT capable devices An API Application Programming Interface in C compatible with the Arduino IDE is developed in order to interface the shield using SPI Serial Peripheral Interface This API allows for two different programming methods polling and events The shield contains a microSD memory card which is used to store audio files that can be played The DECT shield includes three audio outputs to connect headphones speakers and a microphone Tests show the shield allows using common functionalities supported by DECT e g registration audio and data transmission without requiring a background study of DECT Communication with the Arduino using SPI proved to be tolerable to errors because the shield recovers in case of faults and reliable since it is rare to lose messages during heavy SPI usage Speed and range of data and audio communications are within standard DECT values The developed API resulted in a set of simple and easy to understand functions that cover all components in the shield e g speaker volume file playback DECT registration etc A simple cordless telephone system with audio and data communication is implemented in order demonstrate the shield KEYWORDS DECT Wireless Communications Arduino Audio Trans
85. o Martins for the soldering tips My thanks to the INESC ID research institution for allowing me to use their laboratories and equipment during the past months and to Instituto Superior T cnico for its excellent education system want to show my gratitude to my friends and fellow colleagues for their company and friendship To Jo o Marques and Jo o Silva my thanks for the companionship and support during the past 5 years and a special thanks to Hugo Portela for being there when needed during the good and bad moments Finally want to dedicate this thesis to my parents and sister for their unconditional support dedication aid and understanding throughout my degree You were always there for me and will never forget it To you all a huge thanks Without you this would never have been possible ABSTRACT The open source hardware development platform Arduino has been growing in recent years Due to this growth a wide variety of expansion boards shields have emerged with many different purposes in mind from simple logic expansions to Ethernet support Since 2011 there are shields for wireless communication using ZigBee WiFi and GSM but there is not a single one using DECT Digital Enhanced Cordless Telecommunications technology The main advantage of using DECT technology is the possibility to transfer audio data with high reliability up to 100 meters without additional infrastructures or heavy processing like other tech
86. on board regulator However this regulator can only provide 50 mA of current which is not enough for certain situations e g shield transmitting Therefore a 3 3 V regulator 29 is included in the shield to generate 3 3 V from the Arduino 5 V output pin The regulator can output up to 800 mA The Arduino obtains 5 V from the USB connection or from a 5 V linear regulator when being powered by an external source The 5 V pin can output up to 500 mA of current that is enough to power the shield To improve power transmission and mitigate some noise 30 several bypass capacitors are used in the circuit near each component 100 nF ceramic capacitors are adjacent to the power pins of each IC microSD and BDM and a 1 UF is near the BDM antenna circuitry power pin Additionally two electrolytic bypass capacitors are used with the voltage regulator to improve stability and allow peak current surges during DECT transmission bursts or loudspeaker usage One is connected to the regulator 5 V input pin and the other to the 3 3 V output Both have a capacitance of 22 yF 3 3 5 ARDUINO SHIELD INTERFACE The DECT Shield uses six I O ports and power connections from the Arduino An additional optional pin is used to generate events Table 3 3 presents each pin and its functionality 23 Table 3 3 Arduino pins for shield interface Pin Name Description 5V 5 V Power GND Ground 2 INTO Optional Shield Events Signal 8 READ
87. onalities to the Arduino e g Ethernet Wi Fi The main motivation behind this thesis is the lack of low cost DECT development resources and materials as already stated Although there are a variety of DECT capable devices there is not an economic and easy way to interact with them The system implemented in this thesis tries to solve this problem by bringing DECT to the general public Several wireless audio applications created by independent developers and hobbyists are often limited by the technology used Bluetooth has low range Zigbee does not support audio natively Wi Fi VOIP consumes a lot of resources and GSM requires a paid carrier subscription DECT solves some of these issues by providing better distances than Bluetooth supporting audio natively not consuming a vast amount of resources and not requiring a subscription with a cellular operator By combining the Arduino with a shield containing DECT technology it is intended to create a cheap solution which is capable of proving DECT functionalities such as data and audio transmission to the public in a familiar way Hopefully this system will aid developers in applications which were previously limited The final system should be able to serve as a fast prototyping method for application which requires audio support Applications such as intercommunication devices and audio data transmitters need to be easy to implement without spending much time programming or reading
88. onfigs sEvents Event configurations stDECTConfigs sDECT DECT configurations stPlaybackConfigs sPlayback Playback configurations stAudioConfigs sAudio Audio configurations stConfigs Remarks The structures forming stConfigs are described below 68 Structure struct stDECTConfigs Description DECT configuration structure typedef struct uint8 t bAutoAcceptCalls 1 Auto accept incoming calls uint8 t res 7 Reserved stDECTConfigs Remarks Present in stConfigs Structure struct stEventConfigs Description Event configuration structure typedef struct uint8 t bInterrupts uint8 t res union uint8 t nEventMask struct Enable interrupt pin Reserved 1 7 Event mask uint8_t bCallEvents 1 Call events Enabled uint8_t bDataEvents 1 Enable Data Events uint8_t bPlaybackEvents 1 Enable Playback Events uint8 t _res2 6 Reserved E stEventConfigs Remarks Used in stConfigs Structure struct stPlaybackConfigs Description Playback configuration structure typedef struct uint8 t nPrioMode uint8 t res 25 Priority Access 6 Reserved stPlaybackConfigs Remarks Present in stConfigs Structure struct stAudioConfigs Description Audio configuration structure typedef struct stAudioSpeaker sSpeaker Loud Spea
89. orks for home automation such as alarm systems remote doors and wireless sound systems Digital Enhanced Cordless Telecommunications 1 DECT is the second most successfully ETSI European Telecommunications Standard Institute standard after GSM dominating the wireless voice application market with a share of 73 2 It was created primarily for cordless phone systems in Small Office Home Office SOHO applications but currently it is also used in a wide variety of voice and data applications such as baby monitors and traffic lights 3 DECT standard ensures high quality voice transmission without interference up to 100 meters of distance no obstacles not using the highly congested 2 4 GHz spectrum but the licensed 1 8 GHz band Although DECT products are widely commercialized there are not many resources available for independent developers who wish to use it when compared with other wireless technologies e g GSM Wi Fi Zigbee Bluetooth DECT development boards or kits are relatively expensive and hard to acquire requiring direct contact with manufacturers Arduino is a low cost open source hardware development platform being widely used among hackers hobbyists and scientists for small and medium size projects 4 The key aspects of the Arduino are its simplicity ease of use fast prototyping and expansion capabilities High popularity in recent years resulted in a vast number of daughter boards shield that add new functi
90. ption This function changes the speaker and loudspeaker attenuation from O 2dB to 7 12dB Code Example void loop Lf ss Set the speaker attenuation to 2dB maximum volume dect SetSpeakerVolume 0 Lf eds Function EnableMicrophone Arguments None Return Nothing Description This function enables the shield microphone input Function DisableMicrophone Arguments None Return Nothing Description This function disables the shield microphone input 85 Function SetMicrophoneGain Arguments nGain Microphone gain from 0 to 15 Return Nothing Description This function changes the microphone gain from 0 0dB to 15 30dB Code Example void loop J eus Set the microphone gain to its maximum sensitivity of 30dB dect SetMicrophoneGain 15 s Function GetAudioConfigs Arguments None Return stAudioConfigs structure with the current audio configurations Description This function returns the shield audio configurations This information can also be obtained using the GetConfigs function Code Example void loop i s Get shield audio configurations stAudioConfigs sConfigs dect GetAudioConfigs Prints the current speaker volume Serial println sConfigs sSpeaker nVolume DEC AE D 7 MICROSD GROUP FUNCTIONS This group includes t
91. r events DECT dect false void setup stConfigs sConfigs dect GetConfigs amp sConfigs TODO Change shield configurations dect SetConfigs amp sConfigs TODO Apply other configurations void loop TODO Add control code here For a simple DECT link between two shields one needs to be configured as a fixed part and the other as a portable part Firmware configurations are persistent and can be applied using the SetFirmware function 64 Before any audio or data transference the shield working as portable part needs be registered to a fixed part The fixed part can enable registration using the Register function and the portable part can use the Scan function to start scanning for fixed parts The GetScanList function is used afterwards to retrieve the list of fixed parts which were found Registration is established when the portable part executes the Register function with the target fixed part identifier retrieved from GetScanList Both devices need to have the same pin code which can be set using the SetPincode function At any time the fixed and portable parts can use the GetList function to retrieve the identifiers of all registered parts These identifiers are used with the DECT functions to reference other DECT devices Identifier O represents all registered parts The library provides functions to send and receive data packets with up 54 bytes The Send function is used to transmit a data packet
92. reas Distance between the antenna and the BDM needs to be as short as possible Power traces from the BDM RF circuitry needs to be connected to the regulator without ramifications Analog signals need to be separated from digital signals Shield regulator needs to have additional cooper area to improve heat dissipation SPI circuitry should be between the BDM the microSD and the Arduino SPI pins External connectors speaker and microphone should be placed close to each other Power traces should have a width between 16 mil and 40 mil Signal traces should have a width between 10 mil and 16 mil Free circuit area needs to be left with cooper connected to Ground Figure 3 13 presents the final layout The shield measures approximately 77 5 mm by 53 5 mm being slightly larger than an Arduino Uno 25 Figure 3 13 DECT Shield layout rev A Speaker Microphone Arduino Connections Module Loudspeaker Bithium TEST e TL Lr fj medb lt DECT J P Module Micro SD Status LED Power Regulation Arduino Connections The BDM and the antenna are positioned on the right side of the shield in order to avoid the Arduino pins and jacks allowing better reception and transmission The antennas measure 5 cm and are soldered perpendicular to each other forming a 90 angle The speaker filter is near the audio out jack and the microphone filter is near the BDM being as close as possible to the destination in order
93. rence Price Quantity Digikey Reference Digikey Digikey Min Quantity Mouser Reference Mouser Price Mouser Min Quantity 2059528 0 01 50 P1 0GCT ND 1 667 ERJ 3GEYJ1ROV 0 08 1 s 9265724 oroe 10 s 17591 ooe 100 7 175908 ooe 1909 10 11 12 13 14 15 16 17 18 19 21 1759128 oore 100 1759008 oore 10 1759059 oore 100 209941 ooe 1 N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A 604 APHCM2012SURCK 0 18 1236439 0 23 296 8658 1 ND 0 57 595 SN74LVTH125DBR 0 42 1053499 0 80 296 18056 1 ND 0 98 595 SN74AVC4T245PW 0 83 74LVC1G125W5 1469051 0 76 LM1117IMP 3 3CT ND 1 00 926 LM1117IMP3 3NOPB 1 01 N A N A N A 1608405 0 706 1 SC1459 ND 1 23 502 35RAPCABHN2 0 89 1764377 159 1 HR1941CT ND 1 83 798 DM3D SF 1 67 1555981 0122 14 450 1649 ND 0 18 506 FSM2JH 0 18 1716993 027 1 Farnell Digikey and Mouser information regarding references prices and minimum quantity were obtained in July of 2012 Can be bought directly from Bithium and cost approximately 15 N A N A N A N A N A N A N A N A N A N A N A N A N A N A N A 55 B 3 LAYOUT Figure B 3 Bottom copper layer Figure B 4 Bottom
94. rovides a set of functions to be used in Arduino sketches encapsulating the details of the EIL section 2 5 which defines the commands to communicate with the shield These functions use the Protocol layer to communicate with the shield The messages received in the BDM are analyzed by the EIL after been checked by the Protocol layer which verifies their authenticity and executes the desired operation This is the top most layer because it interfaces all the lower level components that are used to communicate with the Arduino and to handle audio reproduction with the ENI DECT communication between shields uses the DECT stack composed by PHY MAC DLC NWK and IWU OSI layers The DECT stack is accessible through the ENI a high level API Other DECT devices can communicate with the DECT Shield because the standard is the same 3 4 2 MESSAGE COMMUNICATION PROTOCOL The Protocol layer Figure 3 16 in the Arduino and the BDM generates and verifies messages used for communication between the DECT Shield and the Arduino Each message contains a command identifier and content associated with a command The layer is capable of detecting errors in received messages and is optimized for SPI usage Figure 3 17 presents the format of the messages supported by the protocol 29 Figure 3 17 Protocol message SOM Command EOM 0xBB ID Body Size Message Body Checksum anny 1 Byte 1 Byte 1 Byte Body Size Bytes 1 Byte
95. ry include lt DECT h gt DECT Class instantiation DECT dect false No events Each function uses the Protocol layer to send a command to the shield and to wait for an answer Error detecting mechanisms with timeouts are implemented preventing the library from locking All functions are executed atomically when events are enabled by disabling the interrupts temporarily The API provides two methods to control the shield polling and events The first method polling uses DECT functions to constantly get the module status and to act based upon the information retrieved The second method generates asynchronous events reporting a status change in the shield Callbacks defined in sketches can be associated to one event and are executed when triggered 33 3 5 APPLICATIONS Table 3 4 presents the sketches developed to test the DECT Shield functionalities The goal was to create a set of examples that cover all developed features present in the shield For instance the Terminal sketch permits to execute and analyze the shield functionalities using a bash terminal through the serial port The Text to speech sketch exemplifies audio playback from the microSD card and the Telephone demonstrates how to create a rudimentary voice telephone between shields Table 3 4 Developed sketches Functionalities tested Sketch Name Events Voice Data Playback Audio Terminal Partial Yes Ye
96. s true Enable Call Events sConfigs sEvents bCallEvents true Enable Playback Events sConfigs sEvents bPlaybackEvents true dect SetConfigs amp sConfigs Lf 25 The description of each structure and function present in this group follows Structure struct stEvent Description Event structure typedef struct enum EventType eEventType 8 Event Type uint8_t nData 2 Date related to the event stEvent Remarks The enum EventType enumerator is described below 87 Structure enum EventType Description Event type enum EventType NoEvent 0 No event DataEvent Data packed available CallEvent Call changed status StoppedPlayingEvent Playback stopped NextFileEvent Next file started playing Function GetEvent Arguments pEvent Pointer to a pre allocated stEvent structure to hold an event Return If the function fails then it return false otherwise true Description This function saves the oldest pending event from the shield inside the pEvent argument Remarks Some events e g receive event aren t removed until their associated information is processed e g read the incoming packet Function attachRecvCallback Arguments recv Pointer to a callback function Return Nothing Description This function attaches a callback to the event triggered when there is a new incoming
97. s Yes Yes Text to speech No No No Yes Yes Telephone Yes Yes Yes Yes Yes A computer is used in all applications to power the Arduino and the shield Additionally the computer is used as a serial terminal printing received data to the monitor and relaying keyboard inputs to the Arduino The Arduino communicates with the computer using the serial port UART emulated by USB Standalone applications without requiring a computer can also be create For example wireless speakers that are powered by an outlet and receive music wirelessly from another shield 3 5 1 TERMINAL The Terminal sketch is a simple Linux bash like terminal that permits to control and analyze the status of the DECT Shield It allows to test and understand how the functionalities supported by the shield work before creating an application to accomplish a certain task Figure 3 20 presents a screenshot of PuTTY a multiplatform terminal running on a PC that is connected to an Arduino running the Terminal sketch The sketch receives and executes the commands through the serial port 34 Figure 3 20 Terminal running on Arduino using PuTTY as interface gp COM6 PuTTY Table 3 5 lists of all commands supported by the application The commands are separated in five groups and each corresponds to one specific set of functionalities supported by the shield These are the following Module Control configure and retrieve status information from th
98. s in order to analyze the shield and Arduino behavior The test showed the EIL detects the invalid messages and discards them as it was programmed to do The Text to speech sketch was executed using a microSD card of 1 GB containing 109 577 different audio files spread across 702 folders occupying a total of 951 MB to analyze the SPI performance between the BDM and the microSD The FAT32 library handled the card correctly but searching a file in a folder with more than 3000 files proved to be slow taking approximately 1 to 2 seconds Shield Responsiveness Communication between the Arduino and the shield is not immediate A test using the oscilloscope was executed to determine the shield maximum delay time to start executing a command after the Arduino sends a message The test showed the BDM can take up to 50 ms to start analyzing a command The measured response times were expected since there is a limitation imposed the ENI The delays consist of the time it takes for the Arduino to transfer a message the time necessary for the BDM to detect a new message and to check for errors The firmware in the BDM requires received messages in the idle loop to wait a maximum of 40 ms for a callback in the ENI to be triggered reducing the responsiveness significantly The time it takes for the shield to respond to the Arduino after executing a command varies greatly from command execution time Measurements show that commands that access the mi
99. sed Table C 6 Commands of the microSD family Command Description 80 sdcardAccess Allows the Arduino to access the memory card 81 sdcardRelease Releases the memory card from the Arduino 62 Appendix D DECT API This appendix contains the documentation for the DECT API library Rev A used to interface the Arduino with the DECT Shield Firstly it presents an overview to explain the basic concepts and operation Afterwards the full function set is listed and a detailed description of each function is provided D 1 LIBRARY OVERVIEW The DECT API is a library developed in C targeted for the Arduino This library implements the interface between the Arduino and the DECT Shield The library functions are separated in six groups as illustrated in Figure D 1 Each group deals with different functionalities supported by the shield Figure D 1 DECT API library groups Module DECT API Library Playback microSD DECT Audio Events Module Configuration and status DECT Control of calls data transmission and registration Playback Reproduction of files stored in the microSD card Audio Configuration of the speaker loudspeaker and microphone microSD Control of the memory card access Events Configuration handling and triggering of events D 2 LIBRARY USAGE Figure D 2 presents the main points to use
100. sible Figure D 5 illustrates the normal state sequence of a call 65 Figure D 5 DECT call states sequence EE AT N Call TN NoCall Pending N AER w d Terminated Accepted reae ME Ongoing A The No Call state can have multiple variants which transmit how the call was terminated e Refused call was refused e Terminated by User call was terminated by the used e Terminated by Destination call was terminated by destination e Disconnected call was lost e g out of range e Invalid Unhandled error should never happen The Call function is used to make accept and refuse calls which in turn change the call states The function is capable of performing one of four actions e Make call attempt to make a call with the target registered part e Accept call accept an incoming call e Refuse call refuse an incoming call e Terminate call terminate an ongoing call A call to all registered parts can be executed using the identifier O The first part to answer the call becomes the endpoint Figure D 6 contains a code snippet exemplifying on how to make a call and wait for the answer of the target device 66 Figure D 6 Arduino exemplification code for making calls void Loop asa Call a registered part and wait for an answer stCallElem sListElem dect Call 1 MakeCall do Only retrieve call slot dect GetCallList amp sListElem 1 while sListEl
101. solder mask 56 Figure B 7 Top silkscreen layer Figure B 8 Drill plan 58 Appendix C EXTERNAL INTERFACE LAYER This appendix contains the description of the commands supported by the External Interface Layer EIL The commands are sent by the Arduino using messages from the Protocol layer to interact with the DECT Shield The EIL processes and executes the commands in the Bithium DECT Module Usage of the EIL is demonstrated in the source code of the DECT API for Arduino Table C 1 lists all commands supported by the EIL The current software version defines 34 different commands and can be extended up to 255 The commands are grouped in families and each family is targeted to a specific set of functionalities supported by the shield Table C 1 List of commands grouped in families Command Families Module DECT Playback Audio microSD moduleVersion dectlnfo playbackPlay audioSpeaker sdcardAccess moduleFirmware dectPincode playbackStop audioLoudspeaker sdcardRelease moduleReset dectList playbackVolume audioVolume moduleDefaults dectSend playbackStatus audioMic moduleStatus dectRecv playbackOpen audioGain moduleConfig dectCall playbackSize audioConfig moduleEvent dectCalllist playbackQueue dectRegister dectUnregister dectScan dectScanlist dectStatus Table C 2 presents the description of commands in the Module family These commands are used to control or g
102. t8 t nElements stDECTStatus GetDECTStatus void The description of each structure and function present in this group follows Structure struct stInfo Description DECT Identifier structure typedef struct union uint8_t nRFPI 5 Radio Fixed Part Identifier uint8_t nIPUI 5 International Portable User Identity stInfo Remarks The Fixed Part firmware uses the RFPI and the Portable Part uses the IPUI Structure struct stPincode Description DECT Pincode structure typedef struct uint8_t n1 4 1st digit uint8_t n2 4 2nd digit uint8_t n3 4 3rd digit uint8_t n4 4 4th digit Optional uint8_t n5 4 5th digit uint8_t n6 4 6th digit uint8_t n7 4 7th digit uint8_t n8 4 8th digit stPincode Remarks Fields n5 through n8 are not used if their values are OxF which means the pincode will have 4 digits 75 Structure struct stListElem Description Element from a list of registered parts typedef struct uint8 t nIdentifier The Identifier used to reference the part union uint8 t nRFPI 5 uint8 t nIPUI 5 Radio Fixed Part Identifier International Portable User Identity h stListElem Remarks The Fixed Part firmware uses the RFPI and the Portable Part uses the IPUI Structure enum CallAction Description Enumerator used to execute a call actio
103. terference in this location 39 An out door test in the countryside a non crowded DECT environment was also executed in order to measure the maximum possible range the shields can achieve without obstacles The test was executed by having one shield stationary and the other moving in a straight line with no obstacles in between The test showed that the communication channel starts showing signs of interference at approximately 60 meters which can be considered the maximum distance without interference in a best case scenario When comparing the communication range with similar shields such as the Bluetooth Shield and the XBee Shield which guaranty communications up to 10 meters and 120 meters respectively the measured values are within expectations even when the BDM contains an antenna problem and the DECT standard ensures reliable communication up to 100 meters Data Transmission Rates Transmission rates were tested using sequences of data packets between two shields The theoretical maximum data rates is of 1 2 kbps since data communication is achieved using DECT control messages instead of dedicated data channels Using control messages to transfer data between shields allows to have an audio channel established and at the same time transmit data in parallel The maximum transmission rates measured during testing were approximately 1 kbps This value is close to the maximum supported rate and is better than expected When compare
104. tion All three variants of the SetPincode function change the pincode in the shield The pin can have 4 or 8 digits that is why there are two similar functions 71 Function GetList Arguments pList Pointer to a pre allocated vector of stListElem structures nElements Number of elements in the pList vector Return Returns the number of elements written in the vector Description This function fills the pList vector with the list of known associated parts These can be Portable Parts if the shield is working as a Fixed Part or Fixed Parts if the shield is working as a Portable Part Code Example Note Function p is a serial printf void loop LL ws uint8 t i j stListElem sList 10 i dect GetList sList 10 if dect LastError Print header Serial println Index IPUI RFPI if i 0 Serial println No parts registered else Print obtained parts information for j pC 2 0 j lt i j d 02X 02X 02X 02X 02X n r sList j nIndex sList j nIPUI sList j nIPUI 1 sList j nIPUI 2 sList j nIPUI 3 sList j nIPUI 4 else Serial println Failed dle us Remarks If the returned value is larger than the maximum number of elements then the shield returned more elements and some didn t fit in the vector Function Send Arguments nIdentifier Shield identifier
105. tors bias the microphone and the two 100 nF capacitors are used to couple the signals before going to the comparator 21 Figure 3 10 Microphone to BDM connections vare Lk 8 MICP T T 100n 2 E MICN 100n S a gt IVREFN 1k 10p 10p The shield also includes a loudspeaker output through a 2 way terminal block Figure 3 11 presents the loudspeaker circuitry and connection The Class D amplifier from the BDM is used and allows to connect a low impedance speaker with at least 4 O The 1 O resistors and the 1 UF capacitors are used to filter high frequency noise from the amplifier Figure 3 11 BDM to loudspeaker connections PAOUTp PAOUTn Bithium DECT Module Loudspeaker lu lu 22 3 3 4 POWER REGULATION AND DISTRIBUTION The current necessary to power the components in the shield is estimated based on the datasheets to define the characteristics of the regulator to be used Table 3 2 contains the average and peak currents of each component present in the shield Table 3 2 Shield average and peak current consumption Component Average current mA Peak current mA BDM 4 5 70 Loudspeaker 500 Logic ICs 4 7 7 2 microSD 0 1 60 Pull ups 1 2 3 5 Total 10 5 140 7 500 In a worst case scenario Table 3 2 the shield consumes 140 7 mA and has 640 7 mA peaks Since the BDM works at 3 3 V it can be powered directly from the Arduino 3 3 V
106. ts Triggered events are saved in this structure and the Arduino can request the oldest pending event from the top of the FIFO Events are removed when requested and discarded if the structure is full A variable array to hold a sequence of WAV files that will be played The array size can be changed and files can be queue into this structure using the Arduino Issuing a play command plays the sequence present in the structure The idle loop in the ENI section 2 5 is used by the EIL to wait for commands and to read audio data from the microSD card during playback Asynchronous callbacks from the ENI are triggered during DECT events and can add new elements to the structures for example when a new data packet is received Non DECT commands which do not use structures changed by the callbacks are executed in the idle loop e g playback commands speaker volume The remaining commands are queued and executed in a callback that is triggered every 40 ms ensuring code atomicity The EIL also contains mechanisms to avoid audio stalls or gaps during playback During a file reproduction the Arduino can continue to communicate with the shield using commands but the response time might be slower The EIL only allows the Arduino to use the SPI bus to transmit a 32 command when an audio block is read from the microSD ensuring that the Arduino has enough time to send and receive a message before a new audio block is required
107. unter Number of pending events stEventStatus Remarks Present in stStatus 70 Structure struct stDECTStatus Description DECT status structure typedef struct stDataStatus sData DECT Data Status stCallStatus sCalls DECT Call Status stDECTStatus Remarks Present in stStatus The structures forming stStatus are described below Structure struct stDataStatus Description DECT data status structure typedef struct uint8 t nDataPackets uint8 t res 3 Number of available data packets 5 Reserved stDataStatus Remarks Present in stDECTStatus Structure struct stCallStatus Description DECT call status structure typedef struct uint8 t nOngoingCalls uint8 t nPendingCalls uint8 t res uint8 t bRegistrationMode 3 Number of ongoing calls 3 Number of pending calls 1 Reserved 1 Registration mode is Enabled stCallStatus Remarks Present in stDECTStatus Structure struct stPlaybackStatus Description Playback status structure typedef struct uint8 t bPlaying uint8 t res uint8 t bUpdated uint8 t bValid 1 File is being played 5 Reserved 1 Data block updated 1 Opened file is valid stPlaybackStatus Remarks Present in stStatus 71 Function LastError Arguments None Return
108. work it was used C in the Arduino C in the BDM firmware and Python in the Text to speech sketch The IAR IDE and Arduino IDE were used for the software development CadSoft Eagle Cad was used for the PCB design and techniques were applied to the shield layout Future work Some improvements and features can easily be added to the shield due to the modular programming model used in the BDM firmware and in the Arduino DECT API The shield schematic is stable but the layout can be improved Some components can be rearranged to make the shield easier to attach to the Arduino For example the loudspeaker 44 connector is on top of the Arduino USB jack resulting in a slight inclination when the shield is mounted on the Arduino Although the BDM supports all DECT functionalities the current firmware version only contains the most common features including registration and wireless voice and data transmission Functionalities such as call handovers walky talky mode and dedicated data channels are not yet implemented These features are application specific and rarely required in small medium projects Nonetheless their implementation and support would be a valuable addition to the shield For now audio reproduction from a file is only supported by a shield working as a fixed part due to limitations in the ENI A new version of the ENI is required to support portable parts Streaming and capturing of an audio file is also limited
109. yet ii ceci beo AR 58 viii Foure B o eo UR EE AE EE vena tr ue e ea OE OR 58 Figure C 1 Shield registration procedure esse ee ee ee AA GR ee ER ee ee ee em eene 61 Figure D 1 DECT API library groups ees ees ee ee ee Re ee mm emm enm AA ee ee AAA nennen ee ee nnns 63 Figure D 2 DECT API library sketch flow seem emm emen 64 Figure D 3 DECT Shield empty sketch for Arduino essem eem 64 Figure D 4 Arduino exemplification code for data transference ee ee ee AR ee AR ee ee ee ee 65 Figure D 5 DECT call states seguenCe ee ese ee ee ee Re AA GR ee een eene nennen be ee ee ee nennen 66 Figure D 6 Arduino exemplification code for making calls ee ee de ee AR AR ee AR ee AR ee ee 67 Figure D 7 Event configuration code ees sse ee ee ee ee ee ee ee ee ee ee ee ee ee ee 87 LisT OF TABLES Table 2 1 DECT characteristics from 5 ese ee ee AA ee ee ee ee ee nennen eene 3 Table 2 2 Characteristics of different wireless technologies extracted from 1 8 6 Table 2 3 Wireless shields characteristics and features sss 9 Table 3 1 SPI pins for Arduino BDM and microSD card ees ee ee ee ee ee ee ee ee ee ee ee ee 16 Table 3 2 Shield average and peak current consumption essen 23 Table 3 3 Arduino pins for shield interface 24 Table 3 4 Developed sketches enne eren enint ee ee nnne 34 Ta

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