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I am trying to interface SIM900 GSM Module with Arduino Mega. When I send AT command on COM port in carriage mode then its not sending 'ok' back so I think the interface is not successful. Here is the resource which I referred to - Link.

Have a look below:-

Code:-

#include <SoftwareSerial.h>     //please put less than and greater than sign respectively in place of  =

SoftwareSerial SIM900(10, 11); // (RX, TX). please zoom image above to see exactly what is going where.

void setup()
{
  SIM900.begin(19200);               // the SIM900 baud rate   
  Serial.begin(19200);  

}

void loop()
{

  if (SIM900.available())              // if date is comming from softwareserial port ==> data is comming from gprs shield
  Serial.write(SIM900.read());
  if (Serial.available())                // if data is available on hardwareserial port ==> data is comming from PC or notebook 
  SIM900.write(Serial.read()); 

}

Electric Connection:-

circuit

How to interface it correctly?

Update:- I added a 5v 2A power supply and changed Arduino Rx/Tx pin to 10/11. Added micro sim at the back but still the same result

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  • You can not power it over the Arduino. The module need up to 2A. The Arduino will never be able to give you all this power. Probably also your USB is not able to do it if connected to a PC.
    – Adriano
    Nov 13, 2019 at 21:13
  • I suspected so. Thanks, will try it. I thought without sim it will draw less power. Nov 14, 2019 at 4:00
  • I added a 5v 2A power supply and changed arduino Rx/Tx pin to 10/11. Added micro sim at the back but still the same result Nov 14, 2019 at 8:08
  • Are the jumpers on the right position? Are you using CR as end line? Is 19200 the right baud rate? Is GND connected correctly? Check this tutorial: randomnerdtutorials.com/sim900-gsm-gprs-shield-arduino
    – Adriano
    Nov 14, 2019 at 11:19
  • 1
    Carriage Return. Some times only LF (Line Feed) is sent.
    – Adriano
    Nov 15, 2019 at 9:53

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