main.cpp

00001 #include "mbed.h"
00002 #define ACK         0x06
00003 #define LF          0x0A
00004 #define CR          0x0D
00005 #define NAK         0x15
00006 #define MESS_LEN    100     // maximum message length
00007 #define MAX_STR     20
00008 #define STR_LEN     40
00009 
00010 //-------------------------------------------------------------------
00011 // Made by G.Pathuis (gpa@quicknet.nl)
00012 // Program reads the information coming from the GPS receiver
00013 // 65 channel SUP500F 10Hz GPS receiver with integrated Smart antenna
00014 // See www.sparkfun.com GPS-09758 for details and documentation
00015 // Hardware information
00016 // SUP500F pin1 -------------MBED p13
00017 // SUP500F pin2 -------------MBED p14
00018 // SUP500F pin3 -------------MBED GND
00019 // SUP500F pin4 -------------MBED Vout (3.3V @ 75mAmp)
00020 // SUP500F pin5 -------------MBED Vout
00021 // SUP500F pin6 -----LED-----MBED GND
00022 // SUP500F pin7 -------------MBED GND
00023 //
00024 // IMPORTANT REMARK-------------------------------------------------
00025 // This receiver has an integrated antenna and will not work when
00026 // situated near a laptop, PC or MBED
00027 // I used connecting (mbed-receiver) wires with a length of 1 meter
00028 //------------------------------------------------------------------
00029 
00030 Serial pc(USBTX, USBRX);    // tx, rx
00031 Serial sup500(p13, p14);    // tx, rx
00032 
00033 char nmea[MESS_LEN] = {0x00};   // raw message from the GPS receiver
00034 char gp[MAX_STR][STR_LEN];      // 40 strings, length is 30
00035 
00036 void read_nmea(void);           // read nmea message from gps module
00037 int chop_message(void);         // chop the nmea messeage
00038 void present_array(void);       // send a part of the available info to the laptop
00039 
00040 int main() {
00041     pc.baud(9600);
00042     pc.format(8,Serial::None,1);
00043 
00044     sup500.baud(9600);
00045     sup500.format(8,Serial::None,1);
00046 
00047     pc.printf("Start lurking...\n\r");
00048     while (1) {
00049         read_nmea();
00050         chop_message();
00051         present_array();
00052     }
00053 }
00054 
00055 //--------------------read nmea from GPS unit--------------------
00056 void read_nmea(void) {
00057     sup500.scanf("%s,",nmea);
00058     //pc.printf("Raw message %s \n\r",nmea); // just for testing
00059 }
00060 
00061 //---------------- chop the nmea message separated by comma's-----------
00062 int chop_message(void) {
00063     for (int k=0; k<MAX_STR; k++) {          // just to make sure thet the char array is set to 0x00
00064         for (int l=0; l<STR_LEN; l++) {
00065             gp[k][l]= 0x00;
00066         };
00067     }
00068     int strcnt=0;                           // string counter
00069     int strpos=0;                           // position inside the string
00070     for (int k=0; k < MESS_LEN; k++) {
00071         if (nmea[k] == '*') {               // detect end of message is found
00072             gp[strcnt][strpos]= 0x00;       // close the string with 0x00
00073             return 0;                       // the work is done, end of this function
00074         }
00075         if (nmea[k] == 0x2c) {             // detect the comma
00076             if (strpos == 0) {
00077                 gp[strcnt][0]= 'E';        // comma at position zero, string must be empty
00078                 gp[strcnt][1]= 'm';        // comma at position zero, string must be empty
00079                 gp[strcnt][2]= 'p';        // comma at position zero, string must be empty
00080                 gp[strcnt][3]= 't';        // comma at position zero, string must be empty
00081                 gp[strcnt][4]= 'y';        // comma at position zero, string must be empty
00082                 gp[strcnt][5]= 0x00;       // comma at position zero, string must be empty
00083             } else {
00084                 gp[strcnt][strpos]= 0x00;   // end the previous string
00085             }
00086             strcnt += 1;                    // increment to the next string
00087             strpos =0;                      // start at position zero
00088         } else {
00089             gp[strcnt][strpos]= nmea[k];    // add char to string
00090             strpos += 1;
00091         }
00092     }
00093     return 0;
00094 }
00095 
00096 // --------------- Dump only $GPGGA on the screen------------------
00097 void present_array(void) {
00098     if ((gp[0][2]=='P') and (gp[0][3]=='G') and (gp[0][4]=='G') and (gp[0][5]=='A')) {
00099         pc.printf("Chop results ");
00100         for (int k=0; k<MAX_STR; k++) {
00101             pc.printf("r%d=%s ",k, gp[k]);
00102         }
00103         pc.printf("\n\r");
00104     }
00105 }