Gsm sim900A not sending sms but showing symbols

Using Arduino Programming Questions
1

The gsm has connected to the network. But yet sms are not sending. Serial monitor is showing some symbols like '@'.
///
Code :

#include <SoftwareSerial.h>

SoftwareSerial SIM900A(2,3);

void setup()
{
  SIM900A.begin(9600);   // GSM Module Baud rate - communication speed 
  Serial.begin(9600);    // Baud rate of Serial Monitor in the IDE app
  Serial.println ("Text Messege Module Ready & Verified");
  delay(100);
  Serial.println ("Type s to send message or r to receive message");


void loop()
{
  if (Serial.available()>0)
   switch(Serial.read())
  {
    case 's':
      SendMessage();
      break;
    case 'r':
      RecieveMessage();
      break;
  }

 if (SIM900A.available()>0)
   Serial.write(SIM900A.read());
}


 void SendMessage()
{ 
  Serial.println ("Sending Message please wait....");
  SIM900A.println("AT+CMGF=1");    //Text Mode initialisation 
  delay(1000);
  Serial.println ("Set SMS Number");
  SIM900A.println("AT+CMGS=\"01884810265\"\r"); // Receiver's Mobile Number
  delay(1000);
  Serial.println ("Set SMS Content");
  SIM900A.println("gsm test");// Messsage content
  delay(100);
  Serial.println ("Done");
  SIM900A.println((char)26);//   delay(1000);
  Serial.println ("Message sent succesfully");
}


 void RecieveMessage()
{
  Serial.println ("Receiving Messeges");
  delay (1000);
  SIM900A.println("AT+CNMI=2,2,0,0,0"); // Eeceiving Mode Enabled
  delay(1000);
  Serial.write ("Messege Received Sucessfully");
 }

Photo given below

Screenshot_5
Screenshot_5872×355 39.6 KB

2

I also tried to send sms by manual AT commands like 'AT+CMGS+' but sms not send rather serial monitor showing 'square blocks' &symbols.

Screenshot_2
Screenshot_2869×357 24.1 KB

3

Welcome to the Forum! Read the forum guidelines to see how to properly ask a question and some good information on making a good post. You will get faster and better help if you post all your code as requested by the forum guidelines.
Please go back and fix your original post.

1 Like
5

This post has the solution of my problem.I'm linking it below -

In the baudrate fixing code i had to make some adjustment to fix the baudrate of gsm 900A mini. If the above code doesn’t fix baud rate then try to change the code like this, which is given below,

//Begin serial communication with Arduino and SIM900A
  SIM900A.begin(115200);
//Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
6

In any case, using 115200 baudrate with SoftwareSerial is not a good idea. The maximum baud of SoftwareSerial is a 38400

7

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