Why can I get GPS fix while Im an GSM mode

Good evening,

I still have difficulties to understand the user of gps and gsm mode. I am sorry.

I worked hard I can have good result.

Here is my code, where I am going to explain.

Note, now, I work wirh Leonardo board instead of UNO

Fiest I turn up the module. I will not past all function as the setup loop works fine
steup()

Code: Select allvoid setup() {  // TURN THE SERIAL AT 9600 baut  Serial.begin(baud_rate);              // Comm to PC  while(!Serial);                       // while the serial stream is not open, do nothing:    #ifdef LEONARDO    Serial1.begin(baud_rate);           // Comm to GPS/GSM    while(!Serial1);                    // while the serial stream is not open, do nothing:  #endif    delay(4000);                          // Wait for 4sec after begin    if(debug)  {    Serial.println(F("\n******************************"));    Serial.println(F("STARTING SYSTEM Read AT stream"));    Serial.println(F("******************************"));  }    // SET THE PIN  pinMode(pin_gsm,OUTPUT);              // Set the pins  pinMode(pin_gps,OUTPUT);  pinMode(pin_power,OUTPUT);  powerUpModule:  // POWER THE MODULE. THE powerUp function will attempt 4 time if AT does not return RDY  if(powerUp(4))                       // Nb of attempt  {      // Enabling GSM mode      gsm_enable();     /*       the gsm_enable does        digitalWrite(pin_gsm,LOW);                //Enable GSM mode        digitalWrite(pin_gps,HIGH);               //Disable GPS mode       delay(2000);     */          // Staring GPS AT+CGPSPWR=1 AT+CGPSRST=0.      if(start_gps())      {        readyToGo = true;        if(debug)        {          Serial.println(F("\n***********"));          Serial.println(F("READY TO GO"));          Serial.println(F("***********\n"));        }      }      else      {        // gps or rst does not return OK        readyToGo = false;        goto powerUpModule;      }  }  else  {    // Could not be poweredUp    if(debug) Serial.print(F("Could not powerup the module."));    readyToGo = false;  } }

From now, I AM ON GSM MODE
Now the loop() loop does simply

Code: Select allvoid loop() {  if(readyToGo)  {    if(debug) serialhwread();     // Check the gps stat     if(gps_stat() > 0)     {       // Display gps fixes       gps_read();     }     delay(5000);      } }

To understand my question, look at the two following function

Code: Select allint gps_stat(void) {  if(debug) Serial.println(F("\n> Getting GPS Stat"));  int val = 0;  if(strstr(read_AT_string("AT+CGPSSTATUS?",3000),"OK") != NULL)  {    if(strstr(buffer,"+CGPSSTATUS: Location Unknown") != NULL)    {      val=0;    }    if(strstr(buffer,"+CGPSSTATUS: Location Not Fix") != NULL)    {      val=1;    }    if(strstr(buffer,"+CGPSSTATUS: Location 2D Fix") != NULL)    {      val=2;    }    if(strstr(buffer,"+CGPSSTATUS: Location 3D Fix") != NULL)    {      val=3;    }  }  else  {    if(debug) Serial.println(F("  Could not get GPS Stat"));    val=0;  }  /*  "Location Unknown": if GPS is not run  "Location Not Fix": after GPS is run ,and haven’t fixed,  "Location 2D Fix" : after GPS status is 2D fixed,  "Location 3D Fix" : after GPS status is 3D fixed.  */  if(debug_buffer)  {    Serial.println(F("------- Show buffer------"));    Serial.println(buffer);    Serial.println(F("-------------------------\n"));  }    return val; }

and

Code: Select all// read data to gps_buf[] from GPS static int gps_read () {    read_AT_string("AT+CGPSINF=2",6000);  Serial.println(F("------- Show buffer------"));  Serial.println(buffer);;  Serial.println(F("-------------------------\n")); }

You can observe, I use the AT command

Code: Select allAT+CGPSSTATUS? AT+CGPSINF=2

After about 20sec, I got fixes while I never switch the GPS mode

Code: Select alldigitalWrite(pin_gps,LOW);                //Enable GPS mode  digitalWrite(pin_gsm,HIGH);                //Disable GSM mode  delay(2000); 

But why!!!!!!

Does the gps mode is a way to receive the GPS fix automoticaly from Serial?
In my case, I can I switch S3 to GSM mode?

Then could you clearly telll me why I have to switch to GPS mode. I carefuly look at the Sketc exemple and particularely to https://www.dfrobot.com/wiki/index.php/G ... indication (The last, at the bottom "GPS Sample Code").
I observed that the GPS mode is enabled at the end of the start_up function, and it stay at the gps mode. I also never observed the command AT+CGPSINF= to get the GPS fixes.

Could you clarify me that. It would be very helpfully.

Many many thank