main.cpp

00001 #include "mbed.h"
00002 // The program sends and receives I2C commands using RealTerm's I2C tab feature
00003 // Run Realterm on PC and this program on mbed
00004 // In RealTerm connect to the mbed's USB virtual COM port
00005 // Switch to I2C tab
00006 // Type in I2C address & data to read and write and see the response
00007 // It is handy to debug complex I2C hardware setups
00008 // Prints "No Ack!" when no I2C device responds to the address
00009 //
00010 // See Instructions at http://mbed.org/users/4180_1/notebook/i2c-debug-for-realterm/
00011 //
00012 DigitalOut myled(LED1);
00013 Serial pc(USBTX, USBRX);
00014 I2C i2c(D14,D15);
00015 
00016 int main() {
00017     pc.baud(9600);
00018     char last_command=0;
00019     char previous_command=0;
00020     char current_char=0;
00021     char address=0;
00022     char data [255];
00023     char current_byte=0;
00024     char cmd[255];
00025     int cmd_count=0;
00026     int data_count=0;
00027     int read=0;
00028     int write=0;
00029     int first_data_byte=0;
00030     int i=0;
00031 
00032     myled=1;
00033     i2c.frequency(100000);
00034     i2c.start();
00035     i2c.stop();
00036     // Send a start message to RealTerm
00037     pc.printf("\fmbed I2C debug tool ready\n\r");
00038     // Scan for I2C devices that reply with ack
00039     for (i=0; i<=254; i=i+2) {
00040         if (i2c.read(i, &data[0], 1) ==0) printf("I2C device detected at address=%2.2X\n\r", i);
00041     }
00042     data[0]=0;
00043     i2c.start();
00044     i2c.stop();
00045 // Loop processing command strings from RealTerm
00046     while (1) {
00047         current_char = pc.getc();
00048         // Is it a two character ASCII string data byte value
00049         if ((current_char <='F') && (current_char !='?')) {
00050             // convert to a binary byte
00051             if (current_char <='9') current_byte = current_char - '0';
00052             else current_byte =current_char +10 -'A';
00053             current_char = pc.getc();
00054             if (current_char >'F') pc.printf("error|\n\r");
00055             if (current_char <='9') current_byte = (current_byte <<4) | (current_char - '0');
00056             else current_byte = (current_byte <<4)|(current_char +10 -'A');
00057             // first byte after S command is the I2C address
00058             if (first_data_byte==1) {
00059                 first_data_byte=0;
00060                 address=current_byte;
00061                 pc.printf(" -I2C address=%2.2X ", address);
00062                 //Odd I2C address is a read and even is a write
00063                 if ((address & 0x01) == 0) write=1;
00064                 else read=1;
00065             } else
00066                 // Read in cmd bytes for write
00067                 if ((last_command == 'S')&&(read==0)) {
00068                     cmd[cmd_count]=current_byte;
00069                     cmd_count++;
00070                 }
00071             // number of bytes for a read
00072             if ((last_command =='R')||(read==1)) data_count=current_byte;
00073         } else {
00074             // Not a number - it is a command character
00075             last_command = current_char;
00076             switch (last_command) {
00077                     // Start
00078                 case 'S':
00079                     if (previous_command == 'S') i2c.start();
00080                     first_data_byte=1;
00081                     break;
00082                     // Stop
00083                 case 'P':
00084                     // Do the I2C write
00085                     if (write==1) {
00086                         pc.printf(" write ");
00087                         if (i2c.write(address,cmd,cmd_count)!=0) pc.printf(" No Ack! ");
00088                         for (i=0; i<cmd_count; i++)
00089                             pc.printf(" cmd=%2.2X ", cmd[i]);
00090                     }
00091                     // Do the I2C read
00092                     if (read==1) {
00093                         pc.printf(" read ");
00094                         if (i2c.read(address, data, data_count) != 0) pc.printf(" No Ack! ");
00095                         for (i=0; i<data_count; i++)
00096                             pc.printf(" data=%2.2X ",data[i]);
00097                     }
00098                     // reset values for next I2C operation
00099                     i2c.stop();
00100                     pc.printf("\n\r");
00101                     read=0;
00102                     data_count=0;
00103                     cmd_count=0;
00104                     write=0;
00105                     first_data_byte=0;
00106                     break;
00107                     // Read after write
00108                 case 'R':
00109                     read=1;
00110                     break;
00111                     // Status request
00112                 case '?':
00113                     pc.printf(" mbed ready \n\r");
00114                     break;
00115                     // Unknown or unimplemented command
00116                 default:
00117                     pc.printf(" unknown command \n\r");
00118                     break;
00119             }
00120             previous_command = last_command;
00121         }
00122     }
00123 }