SIM808 get GPS and parse NMEA string without library

GSM/GPRS Modules SIM808
#1

Hi, i’m trying to use SIM808 to get GPS with my ESP32 but i didn’t found anyway…
Did someone ever triyed and can post his sketch?
I’ will love if someone has a skatch to get NMEA and parse all data without any library…

Anyway i’ve tryied also using TinyGPS and TinyGPS++ library but i’didn’t get it :frowning:
Thank you very much :)!!

#2

You can easily do that by parsing the string byte by byte and feeding into a statemachine.

#3

i’m trying to that usin this code…but i think there are some errors becouse in the loop sometimes it doesn’t work… i’m using it with esp32… wiring is correct becouse sometimes it works…and cheking
my error on internet it says “application attempted to dereference a NULL pointer”

I’m not really good in programming so please if someone have ever done already some sketch help me :slight_smile: thank you very much!

#define mySerial Serial2

char frame[100];
byte GNSSrunstatus;;
byte Fixstatus;
char UTCdatetime[18];
char latitude[11];
char logitude[11];
char altitude[8];
char speedOTG[6];
char course[6];
byte fixmode;
char HDOP[4];
char PDOP[4];
char VDOP[4];
char satellitesinview[2];
char GNSSsatellitesused[2];
char GLONASSsatellitesused[2];
char cn0max[2];
char HPA[6];
char VPA[6];
float latGPS;
float longGPS;


void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
  }
  Serial.println("Serial begin ok");

  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);
  mySerial.println("AT");
  mySerial.println("AT+CGNSPWR=1");
  delay(10000);
}

void loop() { // run over and over
  get_GPS();
  delay(10000);
}


int8_t get_GPS() {

  int8_t counter, answer;
  long previous;

  // First get the NMEA string
  // Clean the input buffer
  while ( mySerial.available() > 0) mySerial.read();
  // request Basic string
  mySerial.println("AT+CGNSINF"); //sendATcommand("AT+CGNSINF", "AT+CGNSINF\r\n\r\n", 2000);

  counter = 0;
  answer = 0;
  memset(frame, '\0', sizeof(frame));    // Initialize the string
  previous = millis();
  // this loop waits for the NMEA string
  do {

if (mySerial.available() != 0) {
  frame[counter] = mySerial.read();
  counter++;
  // check if the desired answer is in the response of the module
  if (strstr(frame, "OK") != NULL)
  {
    answer = 1;
  }
}
// Waits for the asnwer with time out
  }
  while ((answer == 0) && ((millis() - previous) < 2000));
  frame[counter - 3] = '\0';

  // Parses the string
  strtok_single(frame, ": ");
  GNSSrunstatus = atoi(strtok_single(NULL, ","));;// Gets GNSSrunstatus
  Fixstatus = atoi(strtok_single(NULL, ",")); // Gets Fix status
  strcpy(UTCdatetime, strtok_single(NULL, ",")); // Gets UTC date and time
  strcpy(latitude, strtok_single(NULL, ",")); // Gets latitude
  strcpy(logitude, strtok_single(NULL, ",")); // Gets longitude
  strcpy(altitude, strtok_single(NULL, ",")); // Gets MSL altitude
  strcpy(speedOTG, strtok_single(NULL, ",")); // Gets speed over ground
  strcpy(course, strtok_single(NULL, ",")); // Gets course over ground
  fixmode = atoi(strtok_single(NULL, ",")); // Gets Fix Mode
  strtok_single(NULL, ",");
  strcpy(HDOP, strtok_single(NULL, ",")); // Gets HDOP
  strcpy(PDOP, strtok_single(NULL, ",")); // Gets PDOP
  strcpy(VDOP, strtok_single(NULL, ",")); // Gets VDOP
  strtok_single(NULL, ",");
  strcpy(satellitesinview, strtok_single(NULL, ",")); // Gets GNSS Satellites in View
  strcpy(GNSSsatellitesused, strtok_single(NULL, ",")); // Gets GNSS Satellites used
  strcpy(GLONASSsatellitesused, strtok_single(NULL, ",")); // Gets GLONASS Satellites used
  strtok_single(NULL, ",");
  strcpy(cn0max, strtok_single(NULL, ",")); // Gets C/N0 max
  strcpy(HPA, strtok_single(NULL, ",")); // Gets HPA
  strcpy(VPA, strtok_single(NULL, "\r")); // Gets VPA

  //converto stringa in numero per poterla confrontare
  longGPS = atof (logitude); 
  latGPS = atof (latitude);
   
  Serial.println("mia float latitudine");
  Serial.println(latGPS,6);
  Serial.println("mia float latitudine");
  Serial.println(longGPS,6);
  Serial.println("UTCdatetime");
  Serial.println(UTCdatetime);
  Serial.println("latitude"); 
  Serial.println(latitude);
  Serial.println("logitude");
  Serial.println(logitude);
   return answer;  
}


/* strtok_fixed - fixed variation of strtok_single */
static char *strtok_single(char *str, char const *delims)
{
static char  *src = NULL;
char  *p,  *ret = 0;
if (str != NULL)
    src = str;
if (src == NULL || *src == '\0')    // Fix 1
    return NULL;
ret = src;                          // Fix 2
if ((p = strpbrk(src, delims)) != NULL)
{
    *p  = 0;
    src = ++p;
}
else
    src += strlen(src);
return ret;
}