the modem is connected with serial port to a linux host
on that host runs smstools daemon that asks each 20 secs the status of the modem (registered, signal, num of incoming messages)
each minute the daemon sends an custom at command that is handled by the openat app.
when the command is received the openat app simply reset a counter. There is a timer that each 10 minutes increase the counter and if it reaces a value then sends a sms.
The openat app is a watchdog that receives a ping from the host and after a certain number of lost pings the app sends an alert sms.
What happens is that after a while the smstools logs no more the status of the modem and cannot send sms.
I stopped the smstools daemon and connected with minicom to the modem, but there is no way to send commands. The only way to recover is to unplug the power of the modem.
This happens after some days of work.
Don’t think i’am using low level interrupts