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I want my Arduino Micro to interact with my SIM 800 L module. But unfortunately nothing happens, may you can help me figure out where I made a mistake. Here's my wiring:

Arudino Board

SIM-Module

Summary of my wiring:

  • External Battery ---> 800L
  • plus ---> 5VIN
  • minus ---> GND (both in POWER and UART TTL-Section)

  • Arduino ---> 800L
  • RX ---> RXD
  • TX ---> TXD

With that setup I'm using the following code:

#include <SoftwareSerial.h>
#include<Arduino.h>

//Arduino Micro
//SIM 800l


SoftwareSerial mySerial(1, 0); // RX, TX 

void setup()  
{
  // Open serial communication
  Serial.begin(9600);

  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);

  Serial.println("Setup finished");

}

void loop() // run over and over
{
  Serial.println("Sending AT command");
  mySerial.write("AT"); //OK should be returned
  delay(1000);
  //read sim-module response
  Serial.println("Response: ");
  while( mySerial.available() )
  {
    char c = mySerial.read();
    Serial.print(c);
  }

  mySerial.write("at+cmee=2"); //set sim-module into debug mode

  delay(1000);

  mySerial.write("at+cpin?"); //check if pin is necessary


  //read sim-module response
  while( mySerial.available() )
  {
    char c = mySerial.read();
    Serial.print(c);
  }

}

But it gives me the following output as a loop:

 Sending AT command
 Response:
 Sending AT command
 Response:
 Sending AT command
 Response:

And I've noticed that a yellow LED is blinking on the Arduino while running the program so I assume there has to be some input from the SIM800 but I can't read the data at the moment. On the 800L-board itself is also an LED that blinks in an interval of about one second, wich tells you that it has no connection (I live in a relatively remote area) but even if there's no connection shouldn't it still return OK when sending AT?

If you need any further information feel free to ask. I would appreciate every idea you come up with :)

Edit: On the photo the wire goes from the Arduino directly to the 800L but I've changed it so the 800L-power comes from a battery now.

1

Here is some edit in your code

#include <SoftwareSerial.h>
#include<Arduino.h>

//Arduino Micro
//SIM 800l


SoftwareSerial mySerial(9,10); // RX, TX 

void setup()  
{
  // Open serial communication
  Serial.begin(9600);

  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);

  Serial.println("Setup finished");

}

void loop() // run over and over
{
  Serial.println("Sending AT command");
  mySerial.write("AT\r\n"); //OK should be returned
  delay(1000);
  //read sim-module response
  Serial.println("Response: ");
  while( mySerial.available() )
  {
    String c = mySerial.readString();
    Serial.println(c);
  }

  mySerial.write("at+cmee=2\r\n"); //set sim-module into debug mode

  delay(1000);

  mySerial.write("at+cpin?\r\n"); //check if pin is necessary


  //read sim-module response
  while( mySerial.available() )
  {
    String c = mySerial.readString();
    Serial.println(c);
  }

}

Change UART pins to 9,10 as 0,1 are already used in normal serial. Secondly change Seria.read() to Serial.readString() because as far as i know the response is string.

  • Thank you for your advice but I still get nothing returned. Only the RX led on my arduino is blinking but nothing arrives on tx. I tried mapping rxd to txd, put it to port 9,10 then back to the RX,TX ports but nothing gets me a response :/ – Cowboy_Patrick Apr 12 at 11:53
  • sorry I missed on thing. Carriage Return and EOD character are most important part of AT commands. I just see that those are missing. – Vaibhav Apr 12 at 12:05
  • Thank you very very much, retrying some wiring positions and the carriage return did the job its woking now :) – Cowboy_Patrick Apr 12 at 15:32

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