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I am using SIM800L module the module. I am new to GSM modules, so I've searched for the basic to use the GSM with the Arduino. this is my code.

#include <SoftwareSerial.h>

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

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  mySerial.begin(9600);
}

void loop() {
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }

  if (Serial.available()) {
    mySerial.write(Serial.read());
  }
}

when I send any AT commands to the GSM I didn't find any respond, so I changed the baud rate of mySrial and try different rates to get any respond, but I didn't get anything.

The wiring of the circuit is:

  • The 5V of the GSM connected to 5V of a power supply (the maximum current of it is 3A).
  • The GND of the GSM to the GND of the power supply.
  • TX of the GSM to pin 2 of the Arduino.
  • RX of the GSM to pin 3 of the Arduino.
  • GND to to GND of the Arduino.

The module has two LEDs:

  • the first one D6 NET blanking every second.
  • the second one D2 RING blanking every (7, 6, 8 or 9) times of the first one.
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  • 1
    What line ending do you have selected in the serial monitor?
    – Majenko
    Commented May 27, 2022 at 15:18
  • 1
    Both NL & CR and No line ending Commented May 27, 2022 at 16:07
  • try switching RX and TX pins .... on a modem, TX usually means transmit on modem channel, so it should be connected to the Arduino TX pin ... the SIM800L module may have pins labeled same as a modem
    – jsotola
    Commented May 27, 2022 at 18:10
  • You would have to check the wire connections, remember the wire are connected this way. MCU. SIM800 Tx pin -> Rx pin Rx pin -> Tx pin gnd -> gnd if your are using SoftwareSerial library. SoftwareSerial modem(rxdpin, txpin);
    – avong
    Commented May 27, 2022 at 18:45
  • 1
    @hcheung I did it and connect the VDD to 5V of the Arduino but the problem didn't solve. Commented May 28, 2022 at 12:10

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