Arduino UNO & Modem Sim800L Can't write setup commands to send data to server

Question

I am using arduino UNO board, with modem sim800l. I want use it to send data to server, but the problem is that I can't write the setup commands.

What am I doing wrong? Are not this the right commands to use for sim800l? I've tried with different commands and the output is the same.

#include <SoftwareSerial.h>

//Create software serial object to communicate with SIM800L
SoftwareSerial mySerial(3, 2); //SIM800L Tx & Rx is connected to Arduino #3 & #2

void setup()
{
  //Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);

  //Begin serial communication with Arduino and SIM800L
  mySerial.begin(9600);

  Serial.println("Initializing..."); 
  delay(100);
  delay(1000);

  mySerial.println("AT+CMEE=2"); // Error mode 
  delay(100);
  updateSerial();

  mySerial.println("AT"); //Once the handshake test is successful, i t will back to OK
  delay(100);
  updateSerial();

  mySerial.println("AT+CFUN=1"); //Level "full functionality" 
  delay(100);
  updateSerial();

  mySerial.println("AT+CGATT?"); //attach or detach from GPRS service 
  delay(100);
  updateSerial();

  mySerial.println("AT+CSTT=\"net\",\"\",\"\""); //AT+CSTT AT command sets up the apn, user name and password for the PDP context.
  delay(2000);
  updateSerial();

  mySerial.println("AT+CSTT?"); //AT+CSTT show apn
  delay(2000);
  updateSerial();

  mySerial.println("AT+CIICR"); //  Brings up wireless connection
  delay(2000);
  updateSerial();

  mySerial.println("AT+CIFSR"); //  Get local IP address if connected
  delay(2000);
  updateSerial();
}

Here is the output from the console of Arduino IDE:

Initializing... 
AT+CHEE=2 
OK 
AT 
OK 
AT+CFUN=1 
OK 
AT+CGAIT? 
+CGATT: 1 
OK 
AT+CSTT="net","","" 
+CME ERROR: operation not allowed 
AT+CSTT? 
+CSTT: "CMNET","","" 

OK 
AT+CIICR 
+CME ERROR: operation not allowed 
AT+CIFSR 
+CME ERROR: operation not allowed 

Answer 1

You have my sympathies, it took me weeks to get my Arduino talking to the net. I think your problem is happening on the line containing "CSTT", which I don't think SIM800L recognises.

Try the below setup instead, with "SAPBR" in its place:

SoftwareSerial gprsSerial(7, 8); // working here with Arduino ports 7 and 8
void setup() {
  gprsSerial.begin(19200);
  Serial.begin(19200);
  Serial.println("connect to GPRS");
  gprsSerial.println("AT");
  toSerial();
  gprsSerial.println("AT+CREG?");  
  toSerial();
  gprsSerial.println("AT+CGATT?");
  toSerial();
  gprsSerial.println("AT+CSQ ");
  toSerial();
  gprsSerial.println("AT+SAPBR=3,1,\"Contype\",\"GPRS\"");
  delay(2000);
  toSerial();
  gprsSerial.println("AT+SAPBR=3,1,\"APN\",\"" + String(APN) + "\"");
  delay(300);
  gprsSerial.println("AT+SAPBR=3,1,\"USER\",\"" + String(USER) + "\"");
  delay(300);
  gprsSerial.println("AT+SAPBR=3,1,\"PWD\",\"" + String(PWD) + "\"");
  delay(1000);
  toSerial();
  gprsSerial.println("AT+SAPBR=1,1");
  delay(2000);
  toSerial();
  gprsSerial.println("AT+SAPBR=2,1");
  delay(2000);
  toSerial();
}

Your run loop:

void loop(){
// Do your stuff
}

And your toSerial function:

void toSerial()
{
  delay(200);
  if(gprsSerial.available()>0){
    textMessage = gprsSerial.readString();
    delay(100);
    Serial.print(textMessage);    
  }
}

Your call server function should be like this:

void callServer() {
  Serial.println("Calling server");
  gprsSerial.println("AT+CCLK?");
  toSerial();
  gprsSerial.println("AT+HTTPINIT");
  toSerial();
  gprsSerial.println("AT+HTTPPARA=\"CID\",1");
  toSerial();
  gprsSerial.println("AT+HTTPPARA=\"URL\",\"http:[YOURURL]") // NOTE: NOT HTTPS!
  delay(1000);
  toSerial();
  gprsSerial.println("AT+HTTPACTION=0");
  delay(3000);
  toSerial();
  gprsSerial.println("AT+HTTPREAD");
  delay(3000);
  toSerial();
}