Changing RAT manually to GSM causes indefinite reboot loop


Hi folks. I have a problem, I am starting legato with radio OFF, then I am executing cm radio rat GSM, everything seems to be OK, but when I am switching radio on, the module reboots immediately and only solution to make it boot is physically turning the radio off. Then module boots and I have chance to change RAT back to UMTS or AUTO, in these modes legato works perfect. There is no difference, where I am trying to change RAT manually, same scenario appears when I make it from code. Actually, there is one and only case when I can make it change, if I remove a SIM card cm radio rat GSM actually changes RAT and then I can see this change when executing cm radio, but if I insert a SIM, the module reboots again. Is there any chance to make GSM work?

Legato version: 16.07.0
Device: WP8548
Firmware: SWI9X15Y_07.11.09.00 r32989 CARMD-EV-FRMWR1 2016/08/11 18:03:20

Please help!


are you using USB or dcdc power supply?


I am using external power supply (5V 2A), so I am sure it is not a lack of power problem.


I have tried to repeat your test on my unit but dont see the reboot.
Can you do a logread -f ? This will provide more info on your exact failure.


Ok, I have executed logread -f:

root@swi-mdm9x15:~# logread -f
Oct 18 07:00:45 swi-mdm9x15 dropbear[1208]: Child connection from
Oct 18 07:00:45 swi-mdm9x15 authpriv.notice dropbear[1208]: Auth succeeded with blank password for 'root' from
Oct 18 07:00:45 swi-mdm9x15 authpriv.warn dropbear[1209]: lastlog_perform_login: Couldn't stat /var/log/lastlog: No such file or directory
Oct 18 07:00:45 swi-mdm9x15 authpriv.warn dropbear[1209]: lastlog_openseek: /var/log/lastlog is not a file or directory!
Oct 18 07:01:00 swi-mdm9x15 Legato:  INFO | modemDaemon[478]/le_pa T=main | pa_mrc_qmi.c pa_mrc_GetNetworkRegState() 2040 | called

I don’t see anything related to my error.
I have attached failed initialization log, please inspect it. It always restarts after ~5 seconds after powering up.
GSM crash log (21.8 KB)

The interesting thing is when I manually pulled off the SIM card, RAT was successfully changed to GSM:

root@swi-mdm9x15:~# cm radio Power: ON Current Network Operator: RAT: GSM network (LE_MRC_RAT_GSM) Status: Not registered but currently searching for a new operator (LE_MRC_REG_SEARCHING) Signal: Very strong signal strength (5)

Can it be a SIM / cellular operator problem?


Ok, I’ve found the root of the problem.

According to mangOH™ Green (DV4) Developer’s Guide I can use 4.5V to 17V power supply, so I used 5V 2A supply and connected it to DC jack, and 5V seems to be not sufficient for stable work of WP8548, I have tried to connect 12V supply and there is no sudden reboots so far.


thanks for letting us know. Note, that the it is not just the power adaptor voltage rating but also the ability for the adaptor to provide a sudden increase in current as in the case for 2.
We have tested 5V adaptors with no issues.
Anyways, since everything is working it is good to know :slight_smile: