I'm currently battling with a LinkSprite GPRS shield (it's based on the SIMCom SIM900 chip) and seem to have absolutely no luck trying to connect to the network. I've got two SIMs, both of which should be active, but I cannot get the connection light on.
I've got a serial connection going and it's responding to various AT commands, but I can't connect:
is working, and giving me a list of networks, so I think my antenna is good, but
immediately gives me +CREG: 3.
I'm now wondering whether there's a fault with my board, and that it's not seeing the SIM cards. A few commands that I thought would work aren't, for example:
just returns ERROR
Similarly, when trying to read SMS data:
Have I proved that the board isn't seeing the SIM, or is there something definitive I can try?
Thanks in advance!