We are using Thingy:91 X as an evaluation platform for our upcoming product. Our test application is made up of a nested-loop structure like
while(true){
lte_lc_connect();
// handle possible errors
while(true){
//do stuff
error = attempt_to_send();
if(error)
break;
}
lte_lc_offline();
// wait for X minutes
}
Sproadically and seemingly randomly, the modem would get into an unoperational state. When the modem gets into this state, it cannot go out without resetting the whole device. The attempts to connect or disconnect prints the warnings
[20:46:12.849,548] <err> lte_lc: Could not get registration status, error: -1
[20:46:12.849,578]<err> lte_lc: Failed to get current registration status
[20:46:12.849,578] <err> LTE_HTTPS: Failed to connect to LTE network
[20:46:12.849,639] <err> lte_lc: Failed to set functional mode. Please check XSYSTEMMODE.
[20:46:12.849,639] <err> LTE_HTTPS: Could not disable LTE: -14
Trying to talk to the modem from the shell also fails.
at AT
Sending AT command failed with error code -1
This means we have a way of at least detecting the issue. My first question is, is there a way to reset the modem without resetting the whole device.
But more importantly, this looks like an issue in the modem hardware or firmware, so Nordic engineers should look into it.
