 RE: gsm modem interfacing Per Westermark Do you think your processor knows that you have connected a GSM modem? Do you think it needs to know? The main things:
- do you connect the signals to the correct pins.
- correct voltage levels?
- correct baudrate? Inside the processor, it's just serial communication. So look for sample code for serial communication. And when sending/receiving SMS, it's just a standard protocol. So don't limit yourself to 8051 programs when looking for documentation what text strings to send or receive. The documentation for your processor tells you how to make use of the UART. The protocol documentation for your modem tells you what AT commands to use - and if there are special rules for baudrate, pauses, ... The hw documentation for your modem or modem development kit tells you what signals you have available and what levels they have, so you can figure out if they can be connected directly to your UART or if you need any level converters. What steps have yp done? Where are you stuck? | 
