main.cpp

00001 #include "mbed.h"
00002 
00003 #include <vector>
00004  
00005 Serial       pc(USBTX, USBRX); // tx, rx
00006 Serial       c2c(p13, p14);    // tx, rx
00007 DigitalInOut   nREQ(p15);
00008 DigitalInOut   nRDY(p16);
00009 
00010 
00011 // Fletcher checksum calculation, not optimised
00012 static uint16_t checkSum(uint8_t length_byte, uint8_t* buf){
00013     // length is treated as 16-bit for checksum calculation
00014     uint16_t sum1 = length_byte % 255;
00015     uint16_t sum2 = sum1;
00016  
00017     for (int i = 0; i < length_byte; i++) {
00018         sum1 = (sum1 + buf[i]) % 255;
00019         sum2 = (sum2 + sum1) % 255;
00020     }
00021  
00022     return ((sum2 << 8) | sum1);
00023 }
00024 
00025 void sendTestPacket(){
00026     pc.printf("\n\rTX: wait for nRDY... ");
00027     
00028     nREQ = 0;
00029     nREQ.mode(PinMode(OpenDrain));
00030     nREQ.output();
00031     
00032     nRDY = 1;
00033     nRDY.input();
00034     
00035     // wait for nRDY
00036     while(nRDY == 1)
00037         wait(0.1);
00038 
00039     pc.printf("\n\rgot nRDY\n\r");
00040     const uint8_t len = 0;
00041     
00042     c2c.putc(len);
00043     while(!c2c.writeable())
00044         ;
00045     pc.printf("wrote len=%d\n\r", len);
00046     uint8_t data[len==0? 256 : len];
00047     for(int i = 0; i < (len==0? 256 : len); i++){
00048         data[i] = uint8_t((i + 31) & 0xff);
00049         c2c.putc(data[i]);
00050         pc.printf(".");
00051         while(!c2c.writeable())
00052             ;
00053     }
00054     pc.printf("\n\rwrote data\n\r", len);
00055     uint16_t csum = checkSum(len, data);
00056     c2c.putc(uint8_t(csum & 0xff));
00057     while(!c2c.writeable())
00058         ;
00059     c2c.putc(uint8_t((csum >> 8) & 0xff));
00060     pc.printf("\n\rwrote checksum\n\r", len);
00061 }
00062 
00063 void receiveTestPacket(){
00064     pc.printf("RX: wait for nREQ...");
00065     
00066     nREQ = 0;
00067     nRDY = 0;
00068     nREQ.mode(PinMode(OpenDrain | PullUp));
00069     nRDY.mode(PinMode(OpenDrain | PullUp));
00070     nREQ.output();
00071     nRDY.output();    
00072     
00073 //    nREQ.input();
00074 //    nRDY = 1;
00075 //    nRDY.mode(PinMode(OpenDrain));
00076     
00077     while(nREQ == 0)
00078         wait(0.1);
00079         
00080     pc.printf("\n\rgot REQ\n\r");
00081     nRDY = 1;
00082     int len = c2c.getc();
00083     std::vector<uint8_t> msg;
00084     for(int i = 0; i < len; i++)
00085         msg.push_back(c2c.getc());
00086     
00087     uint16_t csum = 0;
00088     for(int i =0; i < 2; i++)
00089         csum |= (uint16_t(c2c.getc()) << (i*8));
00090     
00091     
00092     pc.printf("len=%d\n\r", len);
00093     for(int i = 0; i < len; i++)
00094         pc.printf("0x%x ", msg[i]);
00095     pc.printf("\n\rcsum : 0x%x\n\r", csum);
00096     
00097     uint16_t check_checksum = checkSum(len, &msg[0]);
00098     pc.printf("check: 0x%x\n\r", check_checksum);
00099     
00100     nRDY = 0;
00101 }
00102 
00103 int main() {
00104     pc.printf("\n\r--------\n\rc2c UART Test\n\r");
00105     
00106     c2c.baud(38400);
00107     
00108 //    while(1) {
00109 //        if(c2c.readable()) {
00110 //            pc.putc(c2c.getc());
00111 //        }
00112 //    }
00113     
00114     if(c2c.readable())
00115         pc.printf("Leftover characters:");
00116     while(c2c.readable())
00117         pc.printf("0x%x ", int(c2c.getc()));
00118     pc.printf("\n\r");
00119     
00120     
00121     // receive rx_count things
00122     int rx_count = 1;
00123     while(rx_count > 0){
00124         receiveTestPacket();
00125     }
00126     
00127 //    sendTestPacket();
00128 //    
00129     pc.printf("\n\r--- complete ---\n\r");
00130 }