I want to write an API for ARM7 microcontoller to use unstructured supplementry service (AT+CUSD) to send to a TR800 gsm module. The basic ides is to send a Class-2 msg to the mobile (as in services provided by network providers). I can't seem to find the right method to do it.. I found the command syntax but there was nothing mentioned about the response and exactly when to use different parameters.