I am not currently using an Open AT application but we selling moderate numbers of the Xtend FXT009 modem for use with a product that dials a GPRS connection, negotiates a PPP connection and then runs its own IP stack.
We have had several reports from customers, which I have now duplicated, of the modem’s main RS232 port locking up. I am not sure if this is always the case but I have seen it happen when a PPP session is being shutdown. When this happens the modem is still online and registered and you can communicate with it via the USB port. Via that interface I can see it still thinks there is a GPRS connection active.
In this state the modem will not talk at all on the RS232 port no matter what baud rate or state of the handshaking. The only way to get the serial port alive again is to reset the modem or power cycle it.
This problem seems to be more prevalent on some networks/APNs than others although I do not have enough reports to draw conclusive patterns.
Is anyone out there aware of this problem, the cause and a solution please? I cannot see anything like this being fixed in the firmware revision history.
I have tried running a modem with firmware 7.47 and so far I have not seen the problem reoccur whilst using it, but I would like to know a definite problem has been fixed before recommending users upgrade their firmware.