Issue with GPS in EM7355

We have a fleet of Panasonic CF-53 MK4 laptops with Sierra Wireless EM7355 air cards. We recently switched from using external USB GPS pucks to using the EM7355’s internal GPS receiver for our vehicle tracking software. After the switch over, we began experiencing issues where the vehicles would random disappear off the tracking map. All the laptops are running Windows 10 v20H2 and the tracking software accesses the GPS via the NMEA COM port.

After doing some troubleshooting in these laptops, I found that the COM port was randomly closing and would only reinitialize once either the tracking software or the laptop restarted. I found that the reason the COM port was closing was because the card itself was rebooting as the uptime timer in AT!GSTATUS was being reset. So far, the only way that I have found to reset this timer is using AT!RESET or power cycling the card. I have tested this issue on both the Panasonic recommended driver and the latest driver offered by Sierra Wireless and got the same results.

At this point, I’m out of ideas on where to go next. Does anyone know of a solution to this problem?

Current Time: 267 Temperature: 36
Bootup Time: 5 Mode: ONLINE
System mode: LTE PS state: Attached
LTE band: B13 LTE bw: 10 MHz
LTE Rx chan: 5230 LTE Tx chan: 23230
EMM state: Registered Normal Service
RRC state: RRC Connected
IMS reg state: Full Srv IMS mode: Normal

RSSI (dBm): -32 Tx Power: 0
RSRP (dBm): -55 TAC: A3F4 (41972)
RSRQ (dB): -6 Cell ID: 0FC45CE9 (264527081)
SINR (dB): 30.0


preferred fw version:
preferred carrier name: VZW
preferred config name: VZW_005.029_000
current fw version:
current carrier name: VZW
current config name: VZW_005.029_000

!GVER: SWI9X15C_05.05.58.01 r27044 carmd-fwbuild1 2015/03/05 00:02:40

!GVERBT: SWI9X15C_05.05.58.01 r27044 carmd-fwbuild1 2015/03/05 00:02:40

Revision: 1.1


State: Online
LPM force flags - W_DISABLE:0, User:0, Temp:0, Volt:0, BIOS:0, GOBIIM:0
Poweroff mode: 0
LPM Persistent: 0

PRI Part Number: 9903061
Revision: 05.02

Carrier PRI: 9999999_9902196_SWI9X15C_05.05.16.00_00_ATT_005.009_000
Carrier PRI: 9999999_9902574_SWI9X15C_05.05.16.00_00_GENNA-UMTS_005.007_002
Carrier PRI: 9999999_9902350_SWI9X15C_05.05.37.00_00_SPRINT_005.018_002
Carrier PRI: 9999999_9902266_SWI9X15C_05.05.58.01_00_VZW_005.029_000

VID: 0x1199
APP PID: 0x9041
BOOT PID: 0x9040
Interface: QBI
Manufacturer: Sierra Wireless, Incorporated
Product: EM7355

APP : 9041
BOOT: 9040


You need to figure out what makes the module reset.
Tracking software?

I’m looking into if the tracking software. So far I haven’t found anything to confirm that its responsible. I’m discussing this with the software vendor as well.

Across all these laptops, the reset is occurring at very random intervals, no pattern to them. I have sleep disabled on all laptops.

I spoke with the software vendor and they pulled the log file for their software for one of the affected laptops. At the time the COM port closed, the found numerous break, overrun, and framing error messages which is expected since the COM port was closed.

Are then any documented COM port settings for the NMEA port? I’ve looked but never found any. I’m currently running 9600 bps on all laptops.

Will there be any reset if not running the tracking software?

Please work through Panasonic and capture SwiLogPlus and SwiDiagUtil logs accordingly so that Panasonic can forward the logs to us for further analysis. Thanks.

No if the program is not running it doesn’t reset. I also found that if the program is running but not logged in and note actively using data, the card doesn’t reset. I left the program running in this state over the weekend and it didn’t reset until this morning when I logged into the software.

I’ll get those logs together tomorrow morning when I get into work.

then it means your app makes the module crashed?

That’s what I’m thinking. It’s strange, I’ve not encounter this before. We just started using this program in the last year and just switched to the built in GPS in the last month. Hopefully the SwiLogPlus and SwiDiagUtil logs will provide something. I’m discussing this with the vendor and they are researching it as well.

you can open a tera term terminal to receive the NMEA COM data.
If no reset is seen, that means your tracking application has problem.

I will give that a try tomorrow. Thanks.

Using PuTTY, I connected to the NMEA COM port and left it running all night. After several hours, the air card powered cycled and closed the COM port. The uptimer was reset.

Can you install vmware ubuntu and connect the usb in linux environment?
This can isolate if this is windows problem

Sure, I’ll give that a try.

Ok I got the 7355 working on Ubuntu in a the virtual machine. I left it running over the weekend. When I checked it this morning, the COM port in Linux was closed and the up-timer had been reset.

Then not relate to com port?
Does it reset if no sim card

It doesn’t look like its a COM port issue. GPS data is coming in fine up until the power cycle.
I’ll pull the SIM card in the morning and test it.

I pulled the SIM and got the same results. Could this be a firmware issue in the card?

You can use at!gcclr

After reset, type at!gcdump to see what happens

Ok. I will give that try.