TestBed User Manual [PDF/1177KB]
Contents
1. LNaNI asn Bbz eed NNO2 0291 S wa wj Ed gt Di Pa xT az ja bai Scam m m PS pae EZI EXA ee Se c od Sz ni e mn Si ZE CES bed k Si w TE ES ted ee 660 a ezda ez E Zi EE Ur Z m tate Wd 2 Ls TUI Bed DZ Sta D r sou L t u0 Bhd 6T J SE TUD Std vw Td SL Ei tae lo pb Be bd sy RAL a I Td ONO o n T zi SM pm ao Td H non E HE ata Hi an L t Bid or DENEN 6d O lt nin 5 EEUU 1 ics page Schemati Figure 1 11 5 TECHNICAL DRAWINGS TestBed for mbed Z Z neeus 8 19 T LLOC FOBT zeigt 48uiung uejeig anmu3 04914013 YSPeTATUOAASTA AG Brazo Uo2 0421uT 9 dhU pequ 104 pegiso NNOD Laden did338 JIUNSIS TdS 4ed3aq A0 9dr 9SO 2 ardo 4307105 GGG CD AOAWN a bn 01010101 cccc AWNER idO X IOT GdIBbEZS1 SL l3 20S 338X dS dOUdH3dlNI 0449 GS OHOIMW Sv6560341S 10 123NNO2 d ecWd9 183208 Pweg gsoustw 280 980 sga 90 TIGO 1 0 0SIW ZSSN ONY 13 413 aanza QW3 TSOW 1U0 92 219d AlddNS lao 0971 48 5F4F45 848 0H 2 ics page Schemati Figure 2 12 TestBed for mbed 5 TECHNICAL DRAWINGS X2 o o CN X3 o N N2. Imi att EL Zd Td 8a E a E VOI O H Co 2X ARABBE Aa sBHBHE Ca TX Ed x9 SEO DDDDDDDDD Figure 3 Board Layout 13 TestBed for mbed 5 TECHNICAL DRAWINGS 160 06 UU L Figure 4 Mechanical Drawing 14
3. be set in position 1 2 A male Sub D connector with 9 contacts was used This is in accordance with the CAN stan dard which dictates the following pinout pin no signal name description 1 z 2 CAN L neg signal O A O 7 a m ground 5 6 2 z 7 CAN_H pos signal 8 E 9 2 4 RS485 A Texas Instruments SN65HVD3085ED was chosen as RS485 transceiver IC When the RS485 bus is needed the data receive signal has to be enabled by shortening JD For connecting the bus cable to the TestBed a 3 contact screw terminal was used with X6 Specification of the RS485 being a differential bus system dictates to use a twisted wire pair for connecting the bus devices amongst each other The bus ground signal isn t necessarily to be connected in cases where the bus devices are sharing the same ground potential e g are powered from the same mains line The RS485 should be terminated at both ends with a suitable resistor This termination is necessary to avoid two effects e discharge parasitic capacities generated by the two signal wires of the bus and the several devices on the bus e reduce reflections caused by high signal frequencies at the ends of open wires Attention To use the RS485 functionality the miniature speaker has to be disabled by opening JP6 This is because the mbed signal P21 is used by both functions 2 5 Ethernet The TestBed can be connected to a LAN infras
4. maximum current of 1A The power connector X2 is protected agains wrong polarity voltage is applied to the middle pin the outer ring holds the ground Another possibility to power the TestBed is connecting an USB cable to the mini USB connec tor Please find details in chapter 2 6 on page 6 2 2 Arduino Shields As mentioned in the introduction it is possible to use Arduino hardware on the TestBed This hardware comes in the form of so called shields and are widely available at reasonable prices The very most of the existing shields can be used on the TestBed It must however been taken care of the limitation that TestBed doesn t supply the shield with 9V which some shields need for their operation Also the mechanical part has to be checked the shield socket on the TestBed was designed for the Arduino reference shield Some shields are larger than the reference and therefore won t fit in the socket If a shield fits on the TestBed has to be verified in these cases Another speciality is the difference in signal voltages between mbed1768 and Arduino The mbed1768 uses 3 3V for its GPIO signals whereas the Arduino s voltage is based on 5V As long as there is only digital data transported there is no problem with that The mbed s GPIOs are tolerant to 5V and the Arduino s are interpreting input signals of 2V as logical one T TL level But when the Arduino shield produces analogue signals the mbed shall sample it gets a little compl
5. the mbed The USB host must be able to deliver this current otherwise it can take damage We suggest using a self powered USB hub for connecting the TestBed Attention Don t try to power the TestBed simultaneously by an external mains adapter and the USB connection This can cause serial damages to your setup Always check that JP8 is open if the TestBed is externally powered and the USB connection is used To increase the operating safety a PTC fuse F1 was chosen to avoid currents of more than 500mA drawn out of the USB connection This fuse is self resetting The mini USB connector is intended to allow the usage of the TestBed as an USB device To use the mbed as USB Host or in the OTG mode an other type of USB connector should be used This connector can be wired to the appropriate mbed signals USB and USB by soldering to X8 2 7 micro SD card slot The mbed module offers 512 kB internal and 2 MB externel flash memory but when it comes to memory then more is always better So the TestBed allows the use of micro SD cards to drastically increase the amount of useable non volatile memory SD cards are cheap and very common and therefore are the ideal way of adding swappable memory to an embedded system The connection to the mbed is done via SPI to consume as few signals as possible The card is inserted and taken out by a push push mechanism TestBed supports micro SD cards with a voltage requirement of 3 3V Micro SDHC high capaci
6. ELEKTRONIK LADEN TestBed for mbed TestBed for mbed e ico ee ec e 5 LCD_BL XALLI F 200000012 18666611 11909 9090900990000 LEISURE I GND H 1880 88088000 ee L LJ L ee GNI O SE L we 60000000 66666666 http elmicro com m LCD_CONTRAST ITITITITIITIIIT Axteskiuerttir mbed Development System User Manual TestBed for mbed CONTENTS Contents 1 Introduction 2 Function overview 2 1 Energy AA 2 2 Ardino Shields cesa becomes 2 39 CAN BUS i ta Glan aa Ske A RES 22b ROAST A atu bendy gine aid editar E 2 9 Ethernet ON 2 07 AUS Bos tdeo heredes 2 7 microSD card slot 2 8 XBee socket e 2 9 other interfaces e 2 9 1 Prototyping area 2 9 2 Character LCD 2 9 8 UART interface 3 Combination of peripherals 4 Board configuration 5 Technical Drawings TestBed for mbed 1 INTRODUCTION 1 Introduction The mbed1768 impressively demonstrates the performance of current 32 bit microcontrollers This small controllermodule offers huge possibilities for applications like controlling metering communication and so on But it can get a challenge connecting the mbed to a bus infrastruc ture like LAN or CAN Also the use of a memory card is not as easy as it should be For these connection tasks there are many so called Breakout Boards available most of them with a single purpose Here the TestBed Development System comes into play It offer
7. icated A signal of 3 5V is seen as 7096 from the Arduino shield but will be interpreted as 100 by the mbed This is because the mbed uses a reference in means of maximum voltage of 3 3V So a circuit is needed to adapt the two voltage domains On the TestBed this circuit is implemented as a simple voltage divider that can be selectively switched on and off for each of the Arduino s analogue signals A set jumper JP0 JP5 enables the divider circuit for each of these signals Table 1 explains the correspondance between type of signal and position of those jumpers signal source type of signal position of jumper Arduino analogue closed Arduino digital open or closed mbed1768 digital open Table 1 configuration jumpers of the Arduino interface This kind of voltage adaption can be used only if the source of the analogue signal is preferably high impedance The plain readout of a potentiometer for example will inevitably result in failures This is because the potentiometer acts as a according to the position of its variable contact voltage source of low impedance TestBed for mbed 2 FUNCTION OVERVIEW 2 3 CAN Bus The transveicer IC PCA82C250T from NXP is responsible for connecting the TestBed to a CAN bus infrastructure Using JP9 the CAN bus can be terminated with a 1200 resistor if the TestBed is the last resp the first device on the bus To enable the CAN function JP29 and JP30 have to
8. ide there are the mbed signals P15 to P28 ready to be used in the circuit On top and below the solder grid 3 3V 5V as well as the GND domains are to be found To simplify the connection of a self made data cable to the TestBed a 2x6 connector X_ OPT can be soldered at the right side of the prototyping area The corresponding solderpads to the left TO X OPT can be used to lead the desired signals to the connector 2 9 2 Character LCD For visualisation a standard character display can be attached to the TestBed Communica tion takes place using the 4 bit bidirectional parallel interface The attachment holes as well as the position of the 16 pin connector were made according to a fairly common display type GDM2004D The following dimensional drawing is taken out of the GDM2004D datasheet It can be used to check whether the desired LCD will fit onto the TestBed or not TestBed for mbed 2 FUNCTION OVERVIEW MAX 95 98 0405 Ge 10 0 PITCH2 54x15 38 1 62105 Am 7 Lt foo y 111 d E ug MN us t oo I el laf 7040 76 0 V A 87 3502 930401 The following table illustrates the combination of LCD connector and mbed signal function LCD
9. n be taken from the following table uSD LCD Arduino XBee Eth CAN 485 UART Spkr uSD LCD Arduino XBee Ethernet CAN RS485 UART Speaker SS xo AS USAS eL SEKR SKI lt gt lt lt 1 NEN EN EN SS a EN ENC NEE SIE ESSE E US sol SIS v S X lt S An O means that some signals are shared if the combination will work depends on the needed functionality Combinations marked with an X won t work together A v signals that all should be fine If more than two functions are desired in the application the combination has to be manually according to the board s schematic 4 Board configuration The several board functions of the TestBed are configured using jumpers The following table lists all of these jumpers and their meanings Jumper position function JPO 1 2 Arduino analogue signal AO JP1 1 2 Arduino analogue signal A1 JP2 1 2 Arduino analogue signal A2 JP3 1 2 Arduino analogue signal A3 JES 1 2 Arduino analogee signal A4 JPG 1 2 Arduino analogue signal A5 JP6 1 2 enable speaker IPT 1 2 enable RS485 JP8 1 2 enable power supply from TestBed s mini USB connector JPY 1 2 enable CAN bus termination JP10 1 2 enable CAN bus RX signal Ee 2 3 enable Link Active LED on ethernet jack JP11 1 2 enable CAN bus TX signal Ee 2 3 enable Link Speed LED on etherne
10. s a multitude of interfaces and possibilities for enhancements in combination with the mbed module ready to use and documented The arduos composition of necessary hardware particularly the search for suit able mechanical devices can get exhausting and the often rough and ready style assembly is avoided The mbed s scope of operation increases drastically due to the TestBed compatibility with Arduino hardware there ist nearly no application without a dedicated Arduino Shield Thanks to the enormous calculation power of the Cortex M3 microcontroller the possibilities of these shields are boosted to a higher level compared to the original Arduino controllers The following functions or components are realised on the TestBed e Socket for Arduino Shields e RS485 Interface e CAN Bus e 10 100MBit Ethernet Jack e mini USB Connector e micro SD Slot e Miniature Speaker e XBee Socket s Socket for Character LCD e 2 54mm Prototyping Area e Backup Battery for RTC Functionality e Two Buttons and LEDs as well as one Trim Potentiometer e Reset Button e UART Connector Following the detail descriptions of the seperate hardware elements The naming of connectors and devices are according to the design layout from page 13 TestBed for mbed 2 FUNCTION OVERVIEW 2 Function overview 2 1 Energy supply The energy supply has to take place by a external mains adapter It should output a voltage of 7 9 VDC and be able to deliver a
11. signal mbed signal GND 1 5V 2 Z Contrast 3 RS 4 P26 R W 5 P25 EN 6 P24 DBO 7 DB1 8 DB2 9 DB3 10 DB4 11 P23 DB5 12 P22 DB6 13 P20 DB7 14 P19 Backlight 15 Backlight 16 The SMD resistor R41 comes assembled as 4 70 It can absorb a maximum power of 250mW It was chosen to work with a yellow green lit LCD without a built in series resistor or any other LCD with such a resistor If however a backlighted LCD without a series resistance is used please check carefully if the value of R41 suits the needs of the backlight LED If the resulting current gets too high the LCD s backlight will be destroyed With the potentiometer R40 it is possible to regulate the contrast of the LC display TestBed for mbed 2 FUNCTION OVERVIEW 2 9 3 UART interface X12 was implemented to easily access mbed s UART signals The pinout of this connector matches for example the FTDI USB to UART cable or SparkFun s FTDI basic adapters function X12 signal mbed signal GND 1 2 2 2 F 3 RX 4 P27 TX 5 P28 S 6 E TestBed for mbed 4 BOARD CONFIGURATION 3 Combination of peripherals Caused by the limited GPIO signals available on the mbed not all of the TestBed s peripherals can be used simultaneously Furthermore the mechanical dimensions won t allow to use an Arduino shield and a LCD at the same time Information about which peripherals will work together ca
12. t jack 10 5 TECHNICAL DRAWINGS TestBed for mbed 5 Technical Drawings 67 e248 BETSIET LPVOZ vO 8T s180 ETA ngA 4ayiung uejaig yanmiug DOIT YepepyAUoaySTy Aq ar820 uo2 o042tu 3 d11y Dadu 140 pegisa 3S NOILONQ3 O 6cd S8rXUM EJI 32U3H3lNI S8 SH ZAp Sed 035073 df iA INO aan 09 340 3994831N1 N3dO 2dr NO 32U3t31NI T oe GEG evo s eubrs bo eue 1350719 s eubis ertbip Teuon2841p tq N3dO igh dr unnm adhi EUbrs 79169 329009 JOTYUNY_JINYAZANI MOT 329 3831NI 39910305 asn feo Td AGEI GWSONYN of JJYAYILNI_ NYI l10522328UJd 31 eegen wo L Fas e 329 3H31NI 13NH3HL3 uv m UdS5NT Ki TIVAN XN INYO sy QZT Se HNgO OxH 197 6 u mat Bar 200 axi E 8 vader E z at 9273 GX JINN_93141HS 13031 9071UNU 329UJ83lNI ONIQOHU QqT3IHS ONINOAY era zta Ua ata sed 880 290 sea sea 90 ega zed Tod ea Oe Gu EU zu TU gu 900 SONY IU11910 nE zang TONS ng ene aNd Adds TTX 31naoH daa
13. tructure or simply to another ethernet device The mbed supports comfort features such as Auto MDIX no need for so called crossed patch cables and Auto negotiation automatically determines if the connection has to be 10 or 100 MBit sec The ethernet jack on the TestBed includes a set of magnetics transformers and chokes so damages of either the mbed or other LAN devices are avoided Using the TestBed in a LAN with power over ethernet PoE feature won t destroy the TestBed TestBed for mbed 2 FUNCTION OVERVIEW or the mbed although there is no further use of this feature powering the TestBed via PoE is not possible The transformer s center taps are connected to the solderpads P1 and P2 This can be useful to test the behaviour of the ethernet connection when the center taps are connected to certain voltage levels The both signal LEDs built in the ethernet jack can be used if their corresponding jumpers JP10 and JP11 are set in position 2 3 Doing so disables the CAN bus as both functions share the same mbed signals P29 and P30 The ethernet shielding is connected to the TestBed s ground over a 1nF capacitor able to withstand voltages of up to 2kV 2 6 USB Using the mini USB connector the TestBed can be plugged into a PC USB port By shorting JP8 it is possible to supply the board with power from the USB host Please note The current drawn by the TestBed depends on the peripheral configuration and the program running on
14. ty cards are not supported Attention Never attempt to use the TestBed with a plugged micro SD card without external power supply Otherwise the mbed which is connected to a PC via USB acts as an power supply trough its SPI signal pins Then current flows trough the SD card s internal diode to TestBed s board supply and the mbed could take damage due to current overload The connection to the micro SD card slot is as followed TestBed for mbed 2 FUNCTION OVERVIEW function mbed signal CS P14 MOSI Pil CLK P13 MISO P12 2 8 XBee socket In the last years the XBee formfactor has developed to a quasi standard in integrated RF modules Therefore the TestBed comes populated with a XBee socket So all modules com patible to XBee can be used as long as they depend solely on the serial connection RX TX as these two signals are the only connected pins of the XBee formfactor This is the pinout of the XBee interface function XBee signal mbed signal VCC 1 DOUT 2 P10 DIN 3 P9 GND 10 All the other possible XBee signals are unconnected 2 9 other interfaces 2 9 1 Prototyping area The prototyping area allows the soldering of small extra circuitry directly on the board The solder pads are alligned at a 100mil 2 54mm grid suitable for most common footprints of ICs The area shares its place with an optional LCD or Arduino shield On the left s
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