SIM800L Cant Send Message - arduino

Question

I have a SIM800L module.
I have configured my 800L SIM module, where I connect OUT+ on LM2596 to VCC on SIM800L and OUT- on LM2596 to GND on SIM800L. Besides that, I connect TX SIM800L to pin 2 Arduino and RX SIM800L to pin 3 Arduino
Then, After the source code is uploaded to the arduino mega 2560 board, the SIM800L module flashes 3 times every 3 seconds, sometimes also blinks 7 times every 3 seconds. So on.
And until now my SIM800L module cannot send messages. where is the problem? thanks please answered

Answer 1

First, you must double check that the modem is connected correctly and have enough power. To ensure that I always try to read the output serial of the modem in startup and make a call to it.
If modem starts correctly it should print some data in the serial output (with default settings) and some of them prints the power issues.
You can use the following example to creating a two-way communication between your host PC and the modem. In here I'm using Serial1 with pins 18, 19.
If I remember correctly the blinks should be every 3 seconds, and if it changes it means that modem is being restarted.
After that, you can send AT commands with your host PC and check the functions.
#include <SoftwareSerial.h>
#define serialSIM800 Serial1
void setup()
{
//Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
Serial.begin(9600);
//wait on host serial
while (!Serial);
//Being serial communication with Arduino and SIM800
// you should double check the default baudrate of SIM800 and set it here
serialSIM800.begin(9600);
delay(1000);
Serial.println(“Setup Complete !”);
}
void loop()
{
//Read SIM800 output (if available) and print it in Arduino IDE Serial Monitor
if (serialSIM800.available())
{
Serial.write(serialSIM800.read());
}
//Read Arduino IDE Serial Monitor inputs (if available) and send them to SIM800
if (Serial.available())
{
serialSIM800.write(Serial.read());
}
}