I am trying to use my GSM SIM900A modem to send SMS through my arduino uno. I am not sure if the serial connections are working. I have connected the Rx and Tx of the modem to the Tx and Rx of the arduino respectively. How do i check if the modem is responding? I think i am supposed to send "AT" to the modem and get a response "OK". I am an amateur and i am not quite sure how to feed in the "AT" and where from to expect the response "OK".
I just need to know the modem is responding or not. How do i do it?