interfacing gsm sim900A modem with arduino uno

[arun thapa]

i am unable to send the sms using sim900A and arduino uno,i have made connection,Rx pin of arduino to Tx of sim900A and Tx of ardino to Rx of sim900A modem and common the ground.can any one suggest me solution for this.the code i have been using is

void setup(){

Serial.begin(9600);

delay(500);

Serial.println("AT");

delay(1000);

Serial.println("AT+CMGF=1");

delay(500);

Serial.println("AT+CMGS="+9779804495672"r");

delay(1000);

Serial.println("sms from arduino");

Serial.println(char(26));

delay(1000);

}

void loop()

{

}

[doraemon]

It might be due to Improper Baud Rate.(If you have changed default baud rate of modem from 9600 to other value using AT command)  Make simple test program to check "OK" response from modem when you sent "AT" to it. If battery is not delievering enough current then also SIM900A fail to send message.

[Vara Ashishkumar]

Hye arun,

First check your module is properly working or not. Insert the sim card in GSM module and dial the number ( which inserted in GSM module ) from your phone. GSM module is working if you listening the ring.

Now connect your GSM modulw with PC through UART or RS232. Open any serial terminal like putty, x-ctu or arduino software terminal and enter the simple 'AT' command and check the response of module. If no any response or garbadge value, change your baud rate setting. when you receive 'OK' response from module means your module is working on correct baudrate. Now send the message from serial terminal.If everything will be fine then your code should be work fine.

 

[rupa]

void setup(){

Serial.begin(9600);

delay(200);

}

void loop()

{

Serial.println("AT");

delay(1000);

Serial.println("AT+CMGF=1");

delay(100);

Serial.println("AT+CMGS="+9779804495672"r");

delay(1000);

Serial.println("sms from arduino");

delay(100);

Serial.println(char(26));

delay(1000);

 

}

 

 

here is it simcom900a need external 12 volts supply after giving supply press the power button until u can seen  led with blue light blinks it means ur sim is working connect tx to tx and rx to rx pins of arduino and check it 

[Author]

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