I am trying to use this RPi addon http://imall.itead.cc/raspberry-pi-gsm-add-on.html connected to an RPi running raspbian to send data from a temp sensor to a http service. For this I use pppd to establish a ppp session and transmit data over to the cloud.
I want to detect an incoming voice call while the PPP session in on. I've disabled exclusive lock for pppd on the modem (/dev/ttyAMA0) so that other programs can read data that comes in. When PPP isn't in progress I can see 'RING' appear on the modem serial port when I 'call the modem' from my phone. However I don't see any data coming in when the ppp session is established - any suggestions how I can get around this problem ?
I'm a newbie here and was wondering if keeping the ppp session always open is not an efficient approach. Is there something that can automatically establish a PPP session when an application makes an external call and shutdown the connection after a few minutes of inactivity to save power and increase modem life