SIM900 returns ERROR

Using Arduino Programming Questions
#1

Hey Guys,

I connected a sim900 module (not a shield) to the arduino.
Now i’m working with the SoftwareSerial example to try out some AT commands.

The command ‘AT’ returns ‘OK’. Any other command returns an ERROR. Even the command is returned incompletely. I.e.
The command ‘AT+CMGF=1’ returns

AT+MGF1

ERROR

I tried different commands, they’re all returned incorrect an with an ‘ERROR’ message.

Does anyone have an idea why this happens and how i could solve the problem?

Here’s the sketch i’m using:

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3); // RX, TX

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("Goodnight moon!");

  // set the data rate for the SoftwareSerial port
  mySerial.begin(2400);
  
}

void loop() { // run over and over
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
  if (Serial.available()) {
    mySerial.write(Serial.read());
  }
}

Thanks in advance,
Henning

#2

Which pins is the module connected to ?

#3

2 and 3 as declared in the sketch. Seems as if some signs of the command get lost while transmitting. The command 'AT+CMGS="+1234567890"' returns:

AT+MGS"+1345789"

ERROR
#4