EM7455 reboots constantly

IoT Modules MC/EM Series
1

I have a bunch of EM7455 modems, all of them are updated to latest fw for now, and I have a problem that modems sometimes starts to reboot every ~2 minutes, here is the info from one of them:

at!image?
TYPE SLOT STATUS LRU FAILURES UNIQUE_ID   BUILD_ID
FW   1    GOOD   1   0 0      ??         02.39.00.00?
FW   2    EMPTY  0   0 0
FW   3    EMPTY  0   0 0
FW   4    EMPTY  0   0 0
Max FW images: 4
Active FW image is at slot 1

TYPE SLOT STATUS LRU FAILURES UNIQUE_ID   BUILD_ID
PRI  FF   GOOD   0   0 0      002.085_000 02.39.00.00_GENERIC
Max PRI images: 50

OK

at!priid?
PRI Part Number: 9904609
Revision: 002.085
Customer: Generic-Laptop

Carrier PRI: 9999999_9904609_SWI9X30C_02.39.00.00_00_GENERIC_002.085_000

OK

at!gstatus?
!GSTATUS: 
Current Time:  53		Temperature: 42
Reset Counter: 13		Mode:        ONLINE         
System mode:   LTE        	PS state:    Attached     
LTE band:      B3     		LTE bw:      10 MHz  
LTE Rx chan:   1596		LTE Tx chan: 19596
LTE CA state:  NOT ASSIGNED
EMM state:     Registered     	Normal Service 
RRC state:     RRC Idle       
IMS reg state: No Srv  		

PCC RxM RSSI:  -79		RSRP (dBm):  -111
PCC RxD RSSI:  -77		RSRP (dBm):  -111
Tx Power:      --		TAC:         1EAD (7853)
RSRQ (dB):     -14.6		Cell ID:     0BE73EC8 (199704264)
SINR (dB):     -2.0


OK

at!gcdump

Src:  FatalError
File: ostime_modem.c
Line: 204
Str:  SWI_ABORT-M: timer already running
0000EA60 00000000 00000000 00000000 
Prc:  MPSS
Task: DCC
Time: 0001E1FA
 R0: EC902000  R1: 9E8A2B1D  R2: 9B0B2477  R3: 01112A86  R4: 00009B0B
 R5: 00000000  R6: 0000002A  R7: 00000000  R8: 01112A86  R9: 00000000
R10: 00000011 R11: 15FEEDA5 R12: 00000111 R13: 00000000 R14: 00000001
R15: 00000000 R16: 00000000 R17: 00000000 R18: 0000EA60 R19: 0552F440
R20: 04FA8E40 R21: 9F2A2108 R22: 044A14E0 R23: 0205D3EC R24: 00000000
R25: 00000000 R26: 00000000 R27: 00000000 R28: 00000001 SP:  9F2A2080
FP:  9F2A2088 LR:  0212E370
PC: 02054610
CPSR: 00000000
Mod: Unknown
TOS
9F2A20A8 0212E3C0 044A14E0 9F2A2108 7FFFFFFE 0366C228 00000000
FC759350 9F2A20B0 02054610 9F2A2100 0205DAF8 02AE0C70 7FFFFFFE
9F2A20F8 021A3294 04B2DE40 0205D3EC 7FFFFFFE 00000000 04B2DE40
0205D3EC 04B2DE40 0205D3EC 04B1FAC8 00000000 00000000 04B2DE40
FC759350 0000000A 9F2A21F0 0205D4B8
BOS
App ver: SWI9X30C_02.39.00.00
               

OK

at!err
QDSP6                     ARM9 (not saved)
00   01 seccrypt 00209
01   01 gpstask  04204
02   01 stm      00515
03   01 hdrscmdb 05334
04   01 rdevmap  01604
05   01 gsnvif   00855
06   01 hdridle  00819
07   01 sys_eplm 00691
08   01 mc_recei 02346

OK

at!pcvolt?
Volt state: Normal
Power supply voltage: 3675 mV (ADC: 37094)

Sometimes it can reboot like that for 30 times or more, and sometimes it does not reboot. I tried changing some settings and flags, but no result. Also tried to flash various fw versions from SWI9X30C_02.39.00.00 to SWI9X30C_02.30.01.01, and no result indeed. I found out that if I put modem in LPM mode with AT+CFUN=0, them modem stops rebooting. If I put it back in normal mode, them it starts rebooting again.
Can anyone help with that? I know that EM7455 is EOL, but I have about 30 of them, and I just don’t really want to throw them out.

2

Will the at!gcdump be same if you clear it by at!gcclr ?

Does at!rmareset help on the issue?

Does it reboot in linux?

How about other old firmware?

3

Thanks for response. Looks like it is somehow related to network quality, or providers in my area are doing something with the network, because these reboots can continue for several hours, mainly in the night time, and then all of the tested modems magically stop rebooting, no matter what firmware is installed, old or latest. AT!RMARESET=1 did not help. I’m testing modems in openwrt and debian, as i mainly use them in openwrt, and behavior is consistent. Reboots are happening even with the modem in idle, without data connection/voice calls/etc. And when the modem is not rebooting, it is working perfectly.

4

if data channel is not established for host platform, will there be any reboot?

5

Yes, reboots are happening without data enabled, and stops only if you quickly put the modem in LPM via AT+CFUN=0 before it reboots. If you put it back to normal mode, then after some time (1-2min) it will reboot.

6

if you change another SIM with other operator with better signal strength RSRP, will there be any improvement?

7

I tried to use another operator’s SIM, but it did not help.

8

What if you use other lte band?

9

The providers whose SIMs I tested use different bands, B3 and B20 in my case, so it doesn’t matter what band modem is using.

10

does it work with 3G WCDMA?
Does it relate to antenna?
Did you connect diversity antenna?

11

Sorry, I can’t check with WCDMA only, as both providers, whose SIMs I have, decided to disable WCDMA in most of the areas, mainly where LTE coverage is somewhat good, leaving only GSM and LTE.
It doesn’t matter what antennas I use, I tried antennas with better sensitivity, no changes.
Yes, I’m connecting both main and aux antennas to the module.

12

no idea, never see such crash before

you can see whether there is improvement if using USB 2.0 by AT!USBSPEED
you can see whether there is improvement if shutting down GPS function in AT!USBCOMP

13

I’m already using AT!USBSPEED=0, but not tried to disable GPS, thanks, i will try it

14

Besides shutting down gps, another trial will be to use mbim interface instead of rmnet in at!usbcomp

15

It seems like just disabling GPS with AT!CUSTOM="GPSENABLE",0 helps. I can live without GPS, but proper bugfix in firmware will be nice. Anyway, thanks for helping!