[SOLVED] sim908 return bad speed

Projects Networking, Protocols, and Devices
1

Hello,

I'm reading the sim908 GPS info with getPar functionfrom gsmlib, that internally send an AT+CGPSINF=0 command , all works fine but the speed is always under 60 kph (before convert knots to kph), what is the problem? there is a sim908 problem?

char GPSGSM::getPar(char *str_long, char *str_lat, char *str_alt, char *str_time, char *str_num, char *str_speed)
{
   char ret_val=0;
   char *p_char;
   char *p_char1;
   gsm.SimpleWriteln("AT+CGPSINF=0");
   gsm.WaitResp(5000, 100, "OK");
   if(gsm.IsStringReceived("OK"))
      ret_val=1;
      
   //longitude
   p_char = strchr((char *)(gsm.comm_buf),',');
   p_char1 = p_char+1;  //we are on the first char of longitude
   p_char = strchr((char *)(p_char1), ',');
   if (p_char != NULL) {
          *p_char = 0;
    }
   strcpy(str_long, (char *)(p_char1));
   
   // latitude
   p_char++;
   p_char1 = strchr((char *)(p_char), ',');
   if (p_char1 != NULL) {
          *p_char1 = 0;
    }   
   strcpy(str_lat, (char *)(p_char));
   
   // altitude
   p_char1++;
   p_char = strchr((char *)(p_char1), ',');
   if (p_char != NULL) {
          *p_char = 0;
    }   
   strcpy(str_alt, (char *)(p_char1));
   
   // UTC time
   p_char++;
   p_char1 = strchr((char *)(p_char), ',');
   if (p_char1 != NULL) {
          *p_char1 = 0;
    }   
   strcpy(str_time, (char *)(p_char));   

   // TTFF
   p_char1++;
   p_char = strchr((char *)(p_char1), ',');
   if (p_char != NULL) {
          *p_char = 0;
    }   

   // num
   p_char++;
   p_char1 = strchr((char *)(p_char), ',');
   if (p_char1 != NULL) {
          *p_char1 = 0;
    }   
        strcpy(str_num, (char *)(p_char));

   // speed
   p_char1++;
   p_char = strchr((char *)(p_char1), ',');
   if (p_char != NULL) {
          *p_char = 0;
    }      
   strcpy(str_speed, (char *)(p_char1));   
   
   return ret_val;
}

The fastest retuned value was 29.340792 knots, arround 54.34 kph, but real speed was near 120 kph.

Best regards.

2

Rather than parsing the GPS data, just try printing it. You may not be getting the correct field.

3

Problem solved AT+CGPSINF=0 returns velocity in meters/second not in knots.