I've had intermittent issues with the nrf9160 modem using mfw 1.3.0 with an iBASIS SIM getting stuck in "searching" state when first powering on. The symptoms are similar to this thread:
https://devzone.nordicsemi.com/f/nordic-q-a/57105/nrf9160-modem-stuck-in-searching
but different enough that it doesn't help.
After many days of debugging, I think I see a pattern:
- Modems works fine for a while, set in GPS + LTE mode, connecting and communicating of CAT-M1 and obtaining a GPS fix. This is through many flash and reboot cycles as I develop the software.
- A hard fault occurs during execution due to a software bug. Typically a stack overflow or similar.
- On next boot the modem behaviour is the same, except it does not leave "searching" mode and therefore does not connect.
- Nothing seems to restore normal behaviour, including re-flashing; rebooting; restoring Asset Tracker or Asset Tracker v2 or the AT client firmware and running the LTE Link Monitor; removing and replacing the SIM; running every AT command I can think of including every setting for and combination of CFUN and XSYSTEMMODE; leaving unpowered for a while; reseting various things in nRF Connect for Cloud.
- The only fix I've found is to leave the unit "searching" for around 30 minutes. The unit finally connects as normal and all is well - until I reboot. Then the problem is as it was originally.
- The only persistent fix I've found is to leave the unit "searching" for its requisite 30 minutes or so, then issuing "AT+CFUN=0". After that I can re-flash whatever firmware I like and connections occurs within a few seconds after power on. At least until the next hard fault...
A relevant sample of the log from the LTE Link Monitor appears below:
AT+CFUN?
+CFUN: 1
OK
AT+CGSN=1
+CGSN: "352656106125639"
OK
AT+CGMI
Nordic Semiconductor ASA
OK
AT+CGMM
nRF9160-SICA
OK
AT+CGMR
mfw_nrf9160_1.3.0
OK
AT+CEMODE?
+CEMODE: 2
OK
AT%XCBAND=?
%XCBAND: (1,2,3,4,5,8,12,13,18,19,20,25,26,28,66)
OK
AT+CMEE?
+CMEE: 0
OK
AT+CMEE=1
OK
AT+CNEC?
+CNEC: 0
OK
AT+CNEC=24
OK
AT+CGEREP?
+CGEREP: 0,0
OK
AT+CGDCONT?
OK
AT+CGACT?
OK
AT+CGEREP=1
OK
AT+CIND=1,1,1
OK
AT+CEREG=5
OK
AT+CEREG?
+CEREG: 5,2,"20CA","0808F50D",7
OK
AT%CESQ=1
OK
AT+CESQ
+CESQ: 99,99,255,255,3,45
OK
AT%XSIM=1
OK
AT%XSIM?
%XSIM: 1
OK
AT+CPIN?
+CPIN: READY
OK
AT+CPINR="SIM PIN"
+CPINR: "SIM PIN",3
OK
AT+CIMI
204080813633144
OK
%CESQ: 45,2,3,0
AT+CESQ
+CESQ: 99,99,255,255,5,45
OK
AT+CESQ
+CESQ: 99,99,255,255,2,44
There doesn't seem to be any issues with the APN, network selection or band selection, although the AT+CGDCONT? and AT+COPS? commands take many minutes to return.
AT%XCBAND
%XCBAND: 28
Otherwise there doesn't appear to be any reported issues at all. Even if I turn on AT+CMEE=1, AT+CGEREP=1, AT+CNEC=24 and AT+CEINFO=1, there's never any error.
Any ideas to skip this awful inoperable period?
