Microcontroller › Arduino › interfacing gsm sim900A modem with arduino uno › Hye arun,First check your
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.