Connecting Arduino UNO to SIM800C

Hello all!

I am using an Arduino UNO to communicate with SIM800C(Link to SIM800C: : sim 800C gsm). In the attachment you can see how I connectet the modul to Arduino.

You have to know I have a stable power supply of 5V 2A which is needed. To the TTL I connected 3.3V from a step down converter. TXD is connected to dig 10 and RXD to dig 11 from Arduino and as you can see PWX is connected with GND.

Here is the simple code which I use to try out AT commands:

#include <SoftwareSerial.h>
SoftwareSerial GPRS(10,11);

void setup() {

void loop() {
  while (GPRS.available())

  while (Serial.available())

Baudrate in the Serial Monitor is set to 9600 my problem now is that I get no response from “AT”.

Somehow there must be a problem with my wiring so if anybody knows how to do it correct pleas help me.


Hi, I'm currently having the same problem. Could you ever fix it?

I am facing a problem with sim800c module the tx indicator not lighting up in the ardrino after the connection .
anyone can help me