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1. which allows you to control debug monitor sniff serial devices RS 232 RS 485 RS 422 TTL right from your PC 232Analyzer is a shareware the FREE version has some limitation but is more than enough to test and control your serial devices Click here to download a FREE copy Checksum calculation 232Analyzer comes with a Checksum calculator which allows you to calculate the complicated checksum byte in seconds here is an example Suppose that you are controlling a projector and the projector protocol uses xOR to get the additional checksum byte the command string to turn ON the projector is 1A 2B 3C plus the Checksum byte Use the following procedures to calculate the Checksum byte 1 Select Hex as an operands format 2 Select xOr as an operator 3 Key in the command string and append a comma after each byte of command code e g 1A 2B 3C 4 Click on the Calculate button and you will get the result of OD 0 is omitted Checksum Calculator Operands format f Hex C Dec C Oct C Bin C Asell Operator C And C Or xOr Not Rev bit order l Mod CREC 16 Modbus Input operands fe g 10 11 Result D Calculate Select COM port and Setup communication formats ey Port 5 Baud 19200 Data g Parity Even Stop 1 From the toolbar as shown above you can choose the COM port that is connected to the projector i e Port 5 the Baud rate i e 19200 bps the Data bit i e 8 the2. Parity i e Even and the Stop bit i e 1 Note After you have set up the correct communication formats they must match with the projector s COM port settings click on the Connect button on the left to activate the COM port Setup Flow control Advanced Settings KBX Line State Detection Flow Control Handshaking None DTR ATS can be controlled manually C Software Xon Xoff C Hardware RTS CTS C Both Sotware Hardware Warming Make sure the controlled device use the same Handshaking method program might hang handshaking mismatched Note Advanced settings apply for Debuagging S imulating mode ONLY OK Cancel You can set up the flow control from the window above It could be either Software XON XOFF Hardware RTS CTS Both Software Hardware or None Control your RS 232 devices 1 Control Monitor Line States Rx TX DSR CTS DCD Al DTIR ATS BRKS 232Analyzer allows you to control monitor line states of your COM ports 1 Line states of RTS and DTR will be toggled when the respective LED is clicked you can use a voltage meter to verify the changes you should get 6V to 15V when the line state is ON and 6V to 15V when the line state is OFF 2 Other line states can be monitored through the Virtual LEDs such as RX TX DSR CTS DCD and RI 2 Send Receive commands Communication mode Debugging Simulating Send commands Data icemat TX Appe
3. Pin 3 and Pin 5 of a DB 9 Connector with a Volt Meter if you get a voltage of 3V to 15V then it is a DTE device If the voltage is on Pin 2 then it is a DCE device Note The result for a DB 25 Connector is reversed Please refer to DB 9 to DB 25 conversion table below RS 232 Pinouts DB 9 45 7 A male DB 9 connector viewed from the e front Reverse or back view of male e es connector for Female Connector 6 DSR Data Set Ready 6 DTR Data Terminal Ready 8 CTS leartoSend 8 RTS RequesttoSend ____ 9 RI RingIndicator 9 RI Ring ndicator DB 9 to DB 25 Conversion 1 8 f DCD ata Carrer Detect TxD Transmit Data Ground Signal DSR Data Set Ready Request to Send Clear to Send RS 232 Connections A straight through cable is used to connect a DTE e g computer to a DCE e g modem all signals in one side connected to the corresponding signals in the other side in a one to one basis A crossover null modem cable is used to connect two DTE directly without a modem in between They cross transmit and receive data signals between the two sides and there are many variations on how the other control signals are wired below is one of them Straight through DB 9 Crossover Null Modem DB 9 DTE DCE DTE DTE 1 DCD DCD 1 1 DCD DCD 1 2 RxD TxD 2 2 RxD TxD 3 3 TxD 9 RxD 3 3 TxD RxD 2 4 DTR DS
4. data This is quite important when you are transmitting Binary data as you might need to use these two codes in your data Hardware handshaking makes use of actual hardware lines such as RTS CTS DTR DSR and DCD RI for modem In DTE DCE communication RTS Request to Send is an output on the DTE and input on the DCE CTS Clear to Send is the answering signal coming from the DCE Before sending a data the DTE asks permission by setting its RTS output to high No data will be sent until the DCE grants permission by using the CTS line The DTE uses the DTR Data Terminal Ready signal to indicate it is ready to accept information whereas the DCE uses the DSR signal for the same purpose DTR DSR are normally ON or OFF for the whole connection session e g Off hook while RTS CTS are ON or OFF for each data transmission DCD Data Carrier Ready is used by the modem when a connection has been established with remote equipment while RI Ring Indicator is used by the modem to indicate a ring Signal from telephone line Data formats Binary Hex Dec Oct and ASCII Serial devices use Binary for communication which consists of just two unique numbers 0 and 1 Binary is the Base 2 numbering system One byte of data consists of 8 binary digits from 0000 0000 to 1111 1111 Hexadecimal is the base 16 system which consists of 16 numbers O to 9 and the letters A to F decimal number 15 The Hexadecimal numbering system is useful because
5. it can represent every byte as two consecutive hexadecimal digits and it is easier for humans to read Hexadecimal numbers than Binary numbers Most of the manufacturers use Hexadecimal in their protocol documentation It is simple to convert a value from Hexadecimal to Binary Just translate each Hexadecimal digit into its 4 bit binary equivalent E g Hexadecimal number F3 equals Binary number 1111 0011 Octal refers to the base 8 numbering system which uses just eight unique symbols 0 to 7 Programmers often use Octal format because it is relatively easy for people to read and can easily be translated into binary format each Octal digit represents 3 binary digits E g Octal number 73 equals to Binary number 111 011 Decimal refers to numbers in base 10 which is the numbering system we use most in everyday life It s not as easy as Hexadecimal and Octal to converter Decimal to Binary number but it is easier for us to understand Decimal ASCII American Standard Code for Information Interchange is a character encoding based on the English alphabet ASCII codes both readable and unreadable are widely used in communications such as Modem communications Letters A to Z and numbers O to 9 are readable ASCII codes Some ASCII codes are unreadable such as the control codes XON and XOFF which are used in Software flow control Checksum Many serial protocols use checksum additional bytes added at the end of the data string to check the
6. R 4 4 DTR DSR 6 5 GND GND 5 5 GND GND 5 6 DSR DTR 6 6 DSR DTR 4 7 RTS CTS 7 7 RTS CTS 8 8 CTS RTS 8 8 CTS RTS 7 9 RI RI 9 9 RI RI 9 aa a Null Modem Model CVT Null 1 RS 232 Signals RS 232 Logic Waveform 8N1 The graphic above illustrates a typical RS 232 logic waveform Data format 1 Start bit 8 Data bits No Parity 1 Stop bit The data transmission starts with a Start bit followed by the data bits LSB sent first and MSB sent last and ends with a Stop bit The voltage of Logic 1 Mark is between 3VDC to 15VDC while the Logic 0 Space is between 3VDC to 15VDC RS 232 connects the Ground of 2 different devices together which is the so called Unbalanced connection An unbalanced connection is more susceptible to noise and has a distance limitation of 50 ft which is around 15 meters Step 2 Learn about the Protocol A protocol is one or a few sets of hardware and software rules agreed to by all communication parties for exchanging data correctly and efficiently Synchronous and Asynchronous Communications Synchronous Communication requires the sender and receiver to share the same clock The sender provides a timing signal to the receiver so that the receiver knows when to read the data Synchronous Communication generally has higher data rates and greater error checking capability A printer is
7. SAT 200 INTEGRATION It s as easy as A B C fabsmwireless GSM GPRS Modem l l I i I I l I I l I or Sensor Device The GSM GPRS modem is a highly flexible plug and play modem for direct and easy RS232 integration The Microprocessor can either be a stand alone product or part of the integrated GSM GPRS or other Sensor solution How does it work A Programme the Microprocessor to interface with the device using RS232 protocols B Programme the SAT 202 using the scripting SDK C Connect the SAT 202 using the RS232 cable What do need A SAT 202 User manual to determine the pin connections B Global Tracking GDN 0559 Scripting amp API Command Interface e MM Command to build an 84 bit message to send to the Global Tracking Message Handling System e MR Command to see if the terminal has a channel amp the channel quality i e can it see the satellite e MT Command to check if the message has been sent C Global Tracking SDK application and up loader software to programme the terminal with your bespoke functions What is the Message Content A The Message Payloads 84 bits are as follows Periodic report e Message type 8 bits 0x20 for periodic report Message count Latitude Longitude Speed Heading GPS status Scratchpad 7 Control bits amp Checksum Sensor report Message type Message count Scratchpad 7 Scratchpad 8 Scratchpad 9 Scr
8. a form of Synchronous Communication Asynchronous Communication has no timing signal or clock Instead it inserts Start Stop bits into each byte of data to synchronize the communication As it uses less wires for communication no clock signals Asynchronous Communication is simpler and more cost effective RS 232 RS 485 RS 422 TTL are the forms of Asynchronous Communications Drilling Down Bits and Bytes Internal computer communications consists of digital electronics represented by only two conditions ON or OFF We represent these with two numbers O and 1 which in the binary system is termed a Bit A Byte consists of 8 bits which represents decimal number O to 255 or Hexadecimal number 0 to FF As described above a byte is the basic unit of Asynchronous communications Baud rate Data bits Parity and Stop bit RS 232 Logic Waveform 8N1 The baud rate is the communication speed that measures the number of bit transfers per second For example 19200 baud is 19200 bits per second Data bits are a measurement of the actual data bits in a communication packet For example the above graphic shows eight 8 data bits in a communication packet A communication packet refers to a single byte transfer including Start Stop bits Data bits and Parity If you are transferring a standard ASCII code 0 to 127 7 data bits are enough If it is an extended ASCII code 128 to 255 then 8 data bits are required Parity is a simpl
9. atchpad 10 Control bits amp Checksum 4 bits rolling number incremented at each transmission 21 bits 22 bits 8 bits 4 bits 1 bit 12 bits least significant 12 bits of scratchpad 7 register 4 bit 8 bits 0x21 for sensor report 4 bits rolling number incremented at each transmission 12 bits least significant 12 bits 32 bits 16 bits least significant 16 bits 8 bits least significant 8 bits 4 bit B The scratchpad registers are written to by the microprocessor and the integrator should determine what the most appropriate data should be C To assist in this process the SAT Manager and or Uploader are available on the support site ort satamatics com doc portal technical action technical amp cat program amp srt date amp nam So ftware 20Releases What are the basic Data Transfer Protocols A To send data to our SAT 202 terminal Information parameters from the microprocessor are to be written via serial interface commands to scratchpad registers within the satellite terminal SAT 202 B Data transfer handshake The SAT 202 will set a bit RDY in scratchpad register 6 to a 1 to indicate it is ready to receive data The microprocessor will read RDY and send updated information when RDY is 1 Scratchpad registers 7 to 14 are available for writing information to All scratchpad registers are 32 bits At the end of the transfer the microprocessor needs to write zero to scratchpad regis
10. data integrity as errors might occur during data transmission There are many types of checksum from the simplest uses of it in Modula or BCC to sophisticated CRC calculation Using Modula as an example we learn that before data transmission the sender adds all command bytes together then mod it by 255 decimal to get an additional byte This is to be added at the end of the command string When the receiver receives the command string it will first check the added byte to see whether data remain unchanged or not If that is the case it will accept the data and if not it will ask the sender to resend the data Examples of protocol commands A protocol command is a data string sent from one serial device e g a Computer to another i e a Modem Here are some examples ASCII command example ATI1 lt CR gt lt LF gt to query Modem manufacturer s information Note lt CR gt lt LF gt are the control codes Carriage Return and Line Feed Convert the command string above to Hexadecimal and it becomes 41 54 49 31 0D OA Convert the command string above to Decimal and it becomes 065 084 073 049 013 010 Convert the command string above to Octal and it becomes 101 124 111 061 015 012 Convert the command string above to Binary and it becomes 01000001 01010100 01001001 00110001 00001101 00001010 Step 3 Start controlling your RS 232 devices by using 232Analyzer 232Analyzer is an Advanced Serial Port protocol Analyzer software
11. e way to error check There are Even Odd Mark and Space indicators You can also use no parity For Even and Odd parity the serial port sets the parity bit the last bit after the data bit to a value to ensure that the data packet has an Even or Odd number of logic high bits For example if the data is 10010010 for Even parity the serial port sets the parity bit as 1 to keep the number of logic high bits Even For Odd parity the parity bit is O so that the number of logic high bits is Odd Mark parity simply sets the parity bit to logic high and Space sets the parity bit to logic low so that the receiving party can determine if the data is corrupted Stop bits are used to signal the end of a communication packet This also helps to synchronize different clocks on the serial devices Handshaking Flow Control Handshaking is also called Flow Control The main purpose of Handshaking is to prevent receiver overloading By using Handshaking signals receivers will be able to tell the sending device to pause data transmission if the receiver is overloaded There are three types of handshaking Software handshaking Hardware handshaking and Both Software handshaking uses two control characters XON and XOFF The receiver sends these control characters to pause transmitter during communication XON is decimal 17 and XOFF is decimal 19 in the ASCII chart The drawback of Software handshaking is that these two control characters can not be used in
12. nd L after each byte of command code e g 65 65 Send tae E T AE i Or L Deisy 0 mz Repeat 0 Frequently used commands O00h O0Fh 10h 1Fh Programmable button hex format 1 16 17 32 NUL SOH STX ETX EOT eng ack BEL ATI AT2 AT3 ata ATS ATE AT7 ATE es HT LF Wr FF CRI soj SI s2 s3 s s5 s s7 se Use the above example to control a projector turn ON the projector key in the complete command string 1A 2B 3C 0D into the Send_Command_Pane as shown above note You need to add a sign after each command code and then click on the Send button
13. ter 6 resetting RDY to 0 With RDY 0 the SAT 202 will process the data from the microprocessor and transmit via satellite The SAT 202 will set RDY to 1 when it is ready to receive more data C Serial Commands The Serial Interface is 9600 n 8 1 Commands to the SAT 202 are ASCII characters The SAT 202 echoes all commands replacing the initial upper case command characters with lower case Echoed responses always end in lt LF gt lt CR gt Commands to the terminal should wait for a response to be echoed before another command is sent To write to a scratchpad register use RW 06 nn hhhhhhhh lt CR gt Where nn 2character ASCII hex representation of the register number hhhhhhhh 8 character ASCII hex representation of the 32 bit value to be stored in the register Example RW 06 1F 1234ABCD lt CR gt The terminal will respond with rw 06 1F 12345ABCD lt LF gt lt CR gt To read a scratchpad register use RR 06 nn lt CR gt The terminal will respond with rr 06 nn hHhhhhhhh lt LF gt lt CR gt Tech Note 3 easy steps to understand and control your RS232 devices Step 1 Understand RS 232 Connections amp Signals DTE and DCE DTE stands for Data Terminal Equipment A computer is a DTE DCE stands for Data Communication Equipment A modem is a DCE DTE normally comes with a Male Connector while DCE comes with a Female Connector However that is not always true Use the simple way below to confirm Measure
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