Cant establish a gprs connection

Projects Networking, Protocols, and Devices
1

Hi,
i am new to arduino and trying to get my SIM900 running. At this stage I am testing the module using the "AT"-Commands.

The APN is "pinternet.interkom.de"Found here

Edit:
I noticed that the Sim Module is shutting down after about 10 sec. from starting it. It doesnt do this, when i pull the sim card out.
Is this a problem with the SIM card or the code?
My Code:

#include <SoftwareSerial.h>

SoftwareSerial sim900(2, 3);  // RX, TX Pins des SIM900-Moduls

void setup() {
  Serial.begin(9600);
  sim900.begin(19200);
  delay(2000);  // Warte, bis das SIM900-Modul initialisiert ist

  // Überprüfe die Grundfunktionen des SIM900-Moduls
  checkSIM900Ready();
  checkSIMCardStatus();
  checkSignalStrength();
  configureGPRS();  // GPRS-Verbindung konfigurieren
  establishGPRSConnection();
  checkGPRSConnection();
}

void loop() {
  // Deine weiteren Programmlogik hier
}

void checkSIM900Ready() {
  // Überprüfe die Betriebsbereitschaft des SIM900-Moduls
  sim900.println("AT");
  delay(500);

  while (sim900.available()) {
    String response = sim900.readString();
    Serial.print(response);

    // Überprüfe, ob die Antwort "OK" enthält
    if (response.indexOf("OK") != -1) {
      Serial.println("SIM900 ist betriebsbereit");
      return;
    }
  }

  Serial.println("Fehler: SIM900 ist nicht betriebsbereit");
}

void checkSIMCardStatus() {
  // Überprüfe den Status der SIM-Karte
  sim900.println("AT+CPIN?");
  delay(500);

  while (sim900.available()) {
    String response = sim900.readString();
    Serial.print(response);

    // Überprüfe, ob die Antwort "+CPIN: READY" enthält
    if (response.indexOf("+CPIN: READY") != -1) {
      Serial.println("SIM-Karte ist eingelegt und betriebsbereit");
      return;
    }
  }

  Serial.println("Fehler: Keine SIM-Karte oder SIM-Karte nicht betriebsbereit");
}

void checkSignalStrength() {
  // Überprüfe die Signalstärke
  sim900.println("AT+CSQ");
  delay(500);

  while (sim900.available()) {
    String response = sim900.readString();
    Serial.print(response);

    // Überprüfe, ob die Antwort "+CSQ:" enthält
    if (response.indexOf("+CSQ:") != -1) {
      Serial.println("Signalstärke wurde erfolgreich abgerufen");
      return;
    }
  }

  Serial.println("Fehler: Signalstärke konnte nicht abgerufen werden");
}
void configureGPRS() {
  // Konfiguriere die APN-Einstellungen für die GPRS-Verbindung
  sim900.println("AT+SAPBR=3,1,\"Contype\",\"GPRS\"");
  delay(500);
  sim900.println("AT+SAPBR=3,1,\"APN\",\"pinternet.interkom.de\"");
  delay(500);
  sim900.println("AT+SAPBR=1,1");
  delay(500);
}

void checkGPRSConnection() {
  // Überprüfe die GPRS-Verbindung
  sim900.println("AT+SAPBR=2,1");
  delay(500);

  while (sim900.available()) {
    String response = sim900.readString();
    Serial.print(response);

    // Überprüfe, ob die Antwort "+SAPBR: 1,1" enthält
    if (response.indexOf("+SAPBR: 1,1") != -1) {
      Serial.println("GPRS-Verbindung besteht");
      return;
    }
  }

  Serial.println("Fehler: GPRS-Verbindung konnte nicht hergestellt werden");
}
void establishGPRSConnection() {
  // Überprüfe die GPRS-Verbindung
  sim900.println("AT+CGATT?");
  delay(500);

  while (sim900.available()) {
    String response = sim900.readString();
    Serial.print(response);

    // Überprüfe, ob die Antwort "+CGATT: 1" enthält
    if (response.indexOf("+CGATT: 1") != -1) {
      Serial.println("GPRS-Verbindung besteht");
      return;
    }
  }

  Serial.println("Fehler: GPRS-Verbindung konnte nicht hergestellt werden");
}

The Response i get is

20:52:18.107 -> AT
20:52:18.107 ->
20:52:18.107 -> OK
20:52:18.107 -> SIM900 ist betriebsbereit
20:52:19.675 -> AT+CPIN?
20:52:19.675 ->
20:52:19.675 -> +CPIN: READY
20:52:19.675 ->
20:52:19.675 -> OK
20:52:19.721 -> SIM-Karte ist eingelegt und betriebsbereit
20:52:21.205 -> Signalstärke wurde erfolgreich abgerufen
20:52:24.276 -> AT+SAPBR=3,1,"Contype","GPRS"
20:52:24.276 ->
20:52:24.309 -> OK
20:52:24.309 -> AT+SAPBR=3,1,"APN","pinterFehler: GPRS-Verbindung konnte nicht hergestellt werden
20:52:25.848 -> AT+SAPBR=2,1
20:52:25.848 ->
20:52:25.848 -> +SAPBR: 1,3,"0.0.0.0"
20:52:25.881 ->
20:52:25.881 -> OK
20:52:25.881 -> Fehler: GPRS-Verbindung konnte nicht hergestellt werden

I tried the SIM Card in my mobile and it works without a PIN an can establish a connection to the internet.

What is the problem. Does anyone have any ideas?

Thank you all in advance.

Simon

2

Are you sure it's using GPRS?

Maybe the SIM isn't provisioned for GPRS?

Is there GPRS service at your location?

Note that many networks are phasing-out (sunsetting) 2G & 3G:

Have you tried just issuing the AT commands manually, and seeing what responses you get?

Try AT+CMEE=1 to enable extended error codes

Check SIMCOM documentation for other hints & tips.

3

Hi Awneil,

thank for your help.

Is there GPRS service at your location?

I didn't thought if i am using g2 oder 3 or 4 in my mobile, so i checked it now. I set the settings to "g2 only" and it could establish a connection. So this isnt the problem. But thanks anyway. wasnt aware of this.

Have you tried just issuing the AT commands manually, and seeing what responses you get?

No, but i try it later.

Try AT+CMEE=1 to enable extended error codes

I added the AT+CMEE=1 command but the responses are the same.

I noticed that the Sim Module is shutting down after about 10 sec. from starting it. It doesnt do this, when i pull the sim card out.
Is this a problem with the SIM card or the code?

Thx.

4

Remember that all radio modules take large amounts of current when transmitting, and this tends to be very "peaky".
GSM/GPRS can take peaks of several amps.

A very common problem is that your power supply is not "strong" enough to cope with these peaks, so the voltage drops - and the module can't work.

It's quite possible that the 10s is when the module first tries to transmit...

With no SIM, the module would never try to transmit

5

Thx a lot. It was the power supply. I found a 1 amp power supply at home and it works.

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6

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