I am working with Siemens GSM module and had configured GPRS successfully.But had a doubt,how should i handle call in between when data is being sent by the module?I am using MC55i Siemens module.
While sending data if you get a call & wanna give it a high priority than gprs connection then switch from data mode to command mode using +++ command. Make sure that +++ should be preceded & followed by a delay of at least 1000ms. Also +++ sequence should be entered in a quick succession (within one second).
when you are interfacing a controller with gsm module your data will be sent within very short time so you will not experience the fact that "module cannot accept at commands until number of bytes specified in the last command(AT^SISW) are entered". if you try it with hyper terminal you will get it.