I tried the code shown below (found here)

void setup()
  Serial.begin(9600);  //Baud rate of the GSM/GPRS Module 
  Serial.print("AT+CMGS=\"+919449835011\"\r");    //Number to which you want to send the sms
  Serial.print("Test SMS -Jay\r");   //The text of the message to be sent
void loop()

I interfaced my GSM SIM900A module to the Arduino UNO (connections - GSM Tx to Arduino Rx, GSM Rx to Arduino Tx, GSM provided with supply (12V) using external adapter, GSM gnd to Arduino gnd).

I dumped the code into Arduino and then opened the Arduino IDE serial terminal. In the serial terminal, I get AT+CMGF=1AT+CMGS="+919449835011"Test SMS -Jay\r being displayed and I am not receiving any sms to my phone. I am not sure if its a problem with the code or connections.


looks like you should be using Serial.begin(2400);

also, I'm assuming your sms phone number isn't actually 919449835011 and that that's not actually the number you used in your code

  • Yes that is the number i used in the code, +91 is country code and the rest is the number to which i want to send the sms. I will change the baud rate to 2400 and check.
    – PsychedGuy
    Sep 15 '14 at 7:09
  • 1
    Sorry for the delayed response. This problem was fixed long ago and like you said, I had to just change the baud rate. Thank you.
    – PsychedGuy
    Feb 5 '15 at 8:21

Switch to these pins:

SoftwareSerial mySerial(10, 11); // RX, TX
  • 4
    Welcome to Arduino SE! Can you please edit your post explaining how this solution will fix the issue? Also, are you saying that there should be a hardware switch, too? Thanks! Feb 4 '15 at 16:42
  • The poster may have a point - generally speaking, it can be problematic to share the hardware UART pins between the USB-serial channel and another peripheral. However, for write-only purposes it may be workable, provided one is okay with data going to both places! May 27 '15 at 23:55
  • Yes, I believe the same. Eventually I switched to Software Serial as I wanted to use the UART hardware for debugging and checking the response from my GSM and ESP modules. Another thing, the UART hardware pins can be used for the purpose, however, one needs to use it only after flashing the program. Software Serial works well for baud rates upto 9600 but cannot keep up for higher baud rates. Between the poster has a point, but he/she has not justified the answer.
    – PsychedGuy
    Jul 15 '16 at 4:51

Not the answer you're looking for? Browse other questions tagged or ask your own question.