Introduction. Arduino. October 7, 2014

Transcription

1 1 CB-055 Bluetooth Module October 7, 2014 Introduction This application note will show two minimal code set ups to operate the Bluetooth CB-055, one with an Arduino board and the other with Cardinal s CB-026 Microchip microcontroller module. Arduino The Arduino example will show how to transmit and receive data in SPP mode between the Bluetooth module and a Bluetooth capable PC. We will use a terminal emulator program on the PC to show the characters transmitted from the Bluetooth module and also to send characters. The Arduino code will look for the characters 0 through 8 from the PC and illuminate 0 through 8 LEDs on the IO expander respectively. If it receives an n or N then it will transmit the string Hi, call me Blue back to the PC. Before proceeding any further, please have the Arduino software installed on to your computer. Visit Arduino s user setup guide at for step-by-step instructions. 1 Hardware Parts List: Arduino Uno USB type B connector CB-I-022 Cardinal Interface Board CB-031 IO module CB-055 Bluetooth module Bluetooth enabled PC

2 2 Connect the components as shown in the picture below 2 Plug the CB-I-022 interface into the Arduino Uno board, the CB-055 Bluetooth module into the interface s Electro-Set 6 pin connector and plug the CB-031 IO expander module into the Bluetooth module. Connect the USB cable between the computer and the Arduino Uno. The computer will supply 5 volts through the USB cable which will be regulated on the Arduino interface board to 3.3 volts to run the CB-031 IO expander module and CB-055 Bluetooth module The jumper on the CB-031 can be used to change the slave address of the IO expander module. For this code example we are using 0x20 as the 7-bit slave address so the jumper should be populated as shown in the picture above.

3 3 When the Bluetooth module is powered up it should have been discovered by the Bluetooth enabled PC. It will show with the name XM-16. The first time it is discovered the device needs to be paired, the pair code is On pairing, a virtual COMM port will be created, in practice two COMM ports may be created the lower numbered port is usually the SPP data stream we need. You can use the Windows device manager to show the COMM ports that have been created. We will observe the data arriving at the PC over the Bluetooth SPP protocol by connecting to the COMM port with a terminal emulator such as hyperterm, a program that came with Windows XP or an equivalent terminal emulation program. The Software #include <Wire.h> #define BT_ADDRESS 0x71 #define IO_ADDRESS 0x20 // Wire I2C library // 7 bit I2C Bluetooth address // 7 bit I2C IO_ADDRESS of I/O expander byte numreadbtbytes; byte readbtbyte; unsigned int pout=0; int count=450; int promptlastsent=0; // number of bytes in BT read FIFO / byte read from BT FIFO // value to write to IO expander // used to control timing of when prompt message sent // flag to indicat 3 void writebtstring(char * s); byte readbtbytefmaddr(byte addr); // write string to Bluetooth FIFO // read one byte from Bluetooth register address addr void writeioregister(byte addr, byte dta); // write one data byte to IO expander register address addr void setup() { Serial.begin(9600); Serial.println("Electro-Set"); // initialize serial monitor to 9600 baud // welcome message over Arduino serial monitor poer Serial.println("CB-055 Test"); // welcome message

4 4 Wire.begin(); // initialize I2C port writeioregister(0x00,0x00); writebtstring("\n\n\relectro-set\n\rcb-055 Test\n\r"); // set all 8 IO expander lines as output // BT welcome message, seen on PC terminal void loop() { numreadbtbytes = readbtbytefmaddr(0x01); the receive FIFO // read reg 0x01, the number of bytes present in if (numreadbtbytes>0){ readbtbyte = readbtbytefmaddr(0x03); if ((readbtbyte >= '0') && (readbtbyte <= '8')){ pout=1<<(readbtbyte-'0'); // Get one byte from the receive FIFO // check to see if either 'p' or 'P' // if a 'p' set the pdet flag pout-=1; writeioregister(0x0a,pout); count=0; promptlastsent=0; // reset loop counter 4 if ((readbtbyte =='n') (readbtbyte == 'N')){ writebtstring("\n\rhi, call me Blue"); count=0; // check to see if either 'p' or 'P' // prompt message bytes to send over Bluetooth // reset loop counter promptlastsent=0; if(++count>500){ count=0; if(promptlastsent==0){ // after 500 loops // reset loop counter // prevents consecutive outputs of the prompt writebtstring("\n\rtry typing 0 thro 8 or an 'n'\n\r"); // prompt message bytes to send over Bluetooth promptlastsent=1; // set flag that prompt was last (just) sent

5 5 delay(10); // end of loop() void writeioregister(byte addr, byte dta){ Wire.beginTransmission(IO_ADDRESS); Wire.write(addr); Wire.write(dta); Wire.endTransmission(); // function to write IO expander module // start of I2C transmission to IO // internal register address // data byte to write to register // Complete the I2C transmission void writebtstring(char * s){ Wire.beginTransmission(BT_ADDRESS); Wire.write(0x03); Wire.write(s); Wire.endTransmission(); // function to write string to BT Tx FIFO // start of I2C transmission to Bluetooth // internal register address of FIFO // string to send over Bluetooth // Complete the I2C transmission 5 byte readbtbytefmaddr(byte addr){ Wire.beginTransmission(BT_ADDRESS); Wire.write(addr); Wire.endTransmission(); Wire.requestFrom(BT_ADDRESS, 1); while(wire.available()!= 1); return(wire.read()); Code Operation // function to read byte from BT Rx FIFO // start of I2C transmission to Bluetooth // internal address // Complete the I2C write transmission // Read 1 byte into Wire input buffer // wait for byte // Get byte from wire buffer

6 6 The IO expander module has a 7-bit I2C slave address as 0x20 and the Bluetooth module has a slave address of 0x71 which we also make a #define. The setup() function is called when sketch starts. The setup code, initializes the Arduino serial monitor baud rate at 9600, outputs a welcome message and then initializes the I2C port as a master. Next we initialize the IO expander to have all 8 lines as output by writing 0x00 to the IODIR register 0x00. Finally in Setup we output a welcome message to the PC via the Bluetooth module with the code line: writebtstring("\n\n\relectro-set\n\rcb-055 Test\n\r"); // BT welcome message, seen on PC terminal This function uses the Bluetooth module s internal register address 0x03 which is the transmit/receive FIFO. To transmit data we write to 0x03 as shown in the function definition below. void writebtstring(char * s){ Wire.beginTransmission(BT_ADDRESS); Wire.write(0x03); Wire.write(s); // function to write string to BT Tx FIFO // start of I2C transmission to Bluetooth // internal register address of FIFO // string to send over Bluetooth Wire.endTransmission(); // Complete the I2C transmission 6 After setup has completed, sketch causes the function loop() to be repeatedly called. First we check to see if a byte has been received from the PC. We read the Bluetooth internal register 0x01 which is the count of the bytes in the receive FIFO. The following function reads the number of bytes waiting in the Rx FIFO and puts the value in numreadbtbytes. numreadbtbytes = readbtbytefmaddr(0x01); // read reg 0x01, the number of bytes present If numreadbtbytes is greater than zero we have received data from the PC and we use the same function but with internal register 0x03 to retrieve one byte from the FIFO. readbtbyte = readbtbytefmaddr(0x03); // Get one byte from the receive FIFO We check this to see if the byte is between ASCII 0 and 8, if it is we turn on that number of the LEDs on the IO expander module using the following code: if ((readbtbyte >= '0') && (readbtbyte <= '8')){ pout=1<<(readbtbyte-'0'); // check to see if either 'p' or 'P' // if a 'p' set the pdet flag pout-=1;

7 7 writeioregister(0x0a,pout); Next we check if the received byte is an ASCII n or N, if it is we send a reply message if ((readbtbyte =='n') (readbtbyte == 'N')){ writebtstring("\n\rhi, call me Blue"); // check to see if either 'p' or 'P' // prompt message bytes to send over Bluetooth The bi-directional byte transport has now been shown. Microchip Module CB-026 The CB-026 example in PICBASIC PRO will read the digital acceleration values from each of the 3 axes and display the data through the serial port. The CB-026 example in PICBASIC PRO will show how to transmit and receive data in SPP mode between the Bluetooth module and a Bluetooth capable PC. We will use a terminal emulator program on the PC to show the characters transmitted from the Bluetooth module and also to send characters. The CB-026 code will look for the characters 0 through 8 from the PC and illuminate 0 through 8 LEDs on the IO expander respectively. If it receives an n or N then it will transmit the string Hi, Call me Blue back to the PC. 7 Before proceeding any further, please have the MicroCode Studio PICBASIC PRO suite installed on your computer. Hardware Parts List: Electro-Set module CB-026 microcontroller USB type mini connector CB-055 Bluetooth module CB-031 IO expander module Bluetooth enabled PC with terminal emulator

8 8 Connect the components as shown in the picture below 8 The Software ' I2C Addresses ' $E2 - BluteTooth XM16 ' $40 - IO expander INCLUDE "modedefs.bas" #CONFIG config _HS_OSC & _WDT_OFF & _LVP_OFF & _CP_OFF #ENDCONFIG DEFINE I2C_SLOW DEFINE OSC 20 1 ' ~92kHz I2C clock, 20MHz clk processor 'Set for 20 MHz oscillator

9 9 SCL var PORTC.3 ' Set I2C pins SDA var PORTC.4 Soutpin var PORTC.6 ' Set serial port pins Sinpin var PORTC.7 Baud var WORD rxnumbytes var word ' for serial port baud rate ' bytes received by BT module pout var word ' IO expander output word onebyte var byte Baud=6 ' serial port non inverted pause 10 serout2 soutpin,baud,["electro-set",13,10] ' Welecom message on serial port serout2 soutpin,baud,["cb-055 Test",13,10] i2cwrite sda,scl,$40,$00,[$00],nodata i2cwrite sda,scl,$40,$0a,[$55],nodata ' All 8 lines are output ' Set test pattern 9 ' BT has 3 registers ' 1 FIFO space available for transmit bytes ' 2 Number of receive bytes in FIFO ' 3 Data Port (FIFO) CheckBT: pause 2000 ' BT module pairing/initialization time pause 2000 pause 2000 i2cwrite sda,scl,$e2,$03,["hello",13,10],nodata 'Send welcome string to BT module pause 2000 loopit: i2cread SDA,SCL,$E2,$01,[rxNumBytes.byte0,rxNumBytes.byte1],NoData ' number of bytes received by BT

10 10 if rxnumbytes>0 then if we have anything, get it a byte from the BT module i2cread SDA,SCL,$E2,$03,[oneByte],nodata ' read a byte from BT into variable if onebyte>=48 and onebyte<=56 then onebyte=onebyte-48 ' 48 is '0', 56 is '8' ' 48 is '0' pout=$01<<(onebyte) pout=pout-1 ' turn on zero through 8 LEDs i2cwrite sda,scl,$40,$0a,[pout.byte0],nodata' set the LEDs endif if onebyte=110 or onebyte=78 then ' 110 is 'n', 78 is 'N' i2cwrite sda,scl,$e2,$03,["hi, Call me Blue",13,10],NoData ' Msg to BT module endif goto loopit endif NoData: ' I2C communication failure trap pause Serout2 soutpin,baud,["error",13,10] goto loopit Code Operation The line #CONFIG config _HS_OSC & _WDT_OFF & _LVP_OFF & _CP_OFF includes configuration for the programmer in the output hex file so it does not necessary to manually change the entries in the programmer configuration window every time you come to write a new version of your program to the microcontroller. The port pins for the I2C interface are set on PORTC pins 3 and 4. The CB-026 board wires these to the Electro-Set 6 pin connector. The microcontroller serial port pins are set on PORTC pins 6 and 7, these connect to the FTDI chip on the CB-026 which couples through to the USB and so when plugged into a PC producing

11 11 a virtual COMM port where the microcontroller s serial data can be seen on a terminal emulator such as hyperterminal. The terminal emulator should be set to connect to the virtual COMM port assigned to the FTDI driver and connect at 38400,8,N,1. We declare the variable baud1 for use in the serout2 to set the baud rate. For a baud rate of 38400, baud1 is set to 6, see the MicroChip documentation for other rates and options. The first parameters for the PicBasicPro functions i2cread and i2cwrite uses and 8-bit slave address which is a one bit left shift of the 7-bit slave address, so the Bluetooth module s 8-bit slave address is 0xE2 and the IO expander is 0x40. The Bluetooth module CB-055 I2C interface should be at 100kHz or less so for the 20MHz CB- 026 we need to add the line DEFINE I2C_SLOW 1 ' ~92kHz I2C clock, 20MHz clk processor We set up the I2C and serial port lines, output a welcome message on the serial port and initialize the IO expander to have all 8 lines as output. The Bluetooth module operates in SPP protocol which provides for bi-directional byte data transport. Three internal register addresses are used for this transport: ' BT has 3 registers 11 ' 0x01 FIFO space available for transmit bytes, size word ' 0x02 Number of receive bytes in FIFO, size word ' 0x03 Data Port (FIFO), size up to 512 bytes Reading 0x01 returns the number of bytes of space available for a transmit message, it is word i.e. two bytes sent LSB byte first. The transmit messages are buffered in a FIFO, once you know sufficient space for your message is available in the FIFO, the message should be written to 0x03, the FIFO. In a similar manner register 0x02 has the number of bytes received over the air by the by the Bluetooth module, reading register 0x03, the FIFO retrieves these bytes. We write a simple welcome message Hello to the Bluetooth FIFO. On the PC a terminal emulator should be connected to the virtual comm port to interact over the Bluetooth connection. Hello should be displayed by the terminal. We enter the main loop of the code. loopit: i2cread SDA,SCL,$E2,$01,[rxNumBytes.byte0,rxNumBytes.byte1],NoData ' number of bytes received by BT

12 12 if rxnumbytes>0 then if we have anything, get it a byte from the BT module i2cread SDA,SCL,$E2,$03,[oneByte],nodata ' read a byte from BT into variable if onebyte>=48 and onebyte<=56 then onebyte=onebyte-48 ' 48 is '0', 56 is '8' ' 48 is '0' pout=$01<<(onebyte) pout=pout-1 ' turn on zero through 8 LEDs i2cwrite sda,scl,$40,$0a,[pout.byte0],nodata' set the LEDs endif if onebyte=110 or onebyte=78 then ' 110 is 'n', 78 is 'N' i2cwrite sda,scl,$e2,$03,["hi, Call me Blue",13,10],NoData ' Msg to BT module endif goto loopit endif First we test if any bytes have been received by the Bluetooth module, if none then we loop around and test again, waiting for a byte to be sent over the air from the PC terminal. Once the module receives a byte then the variable rxnumbytes will not be zero anymore, we read one byte from the FIFO into the variable onebyte. 12 i2cread SDA,SCL,$E2,$03,[oneByte],nodata ' read a byte from BT into variable Our code tests onebyte, if it is from 48 to 56, i.e. 0 through 8, we turn it into a byte value 0 through 8 and compute pout to have that number of 1 s, and set the LEDs on the IO Expander module. We then test onebyte for 110 or 78 if it is either we send a string back to the PC. So we have now demonstrated the bi-direction flow over Bluetooth. This can be expanded to a more complex packet transfer scheme if the application so needs.