Ubuntu: nRF Util's "Trace" command "Failed to decode modem trace: failed to fill whole buffer (error code 100)"

[Devon W]

I am using a LattePanda 3 Delta running an Ubuntu server OS (x86) headlessly. I am using a RS-232 cable to obtain the modem trace from my custom board, which uses an nRF9160.
When I run nRF Connect for Desktop (with GUI) on my Windows machine, I am able to obtain a trace easily.

Versions:
nrfutil==7.12.0
nrfutil trace==3.0.0

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On my Ubuntu machine, the trace runs without issue (see output 1 below) UNTIL IT REACHES approx. 13KB, at which it displays an error message (see output 2 below).

Command:
sudo nrfutil trace lte --input-serialport "/dev/ttyUSB0" --output-pcapng ~/nrfutil/logs/out3.pcapng

Output 1:
Saving trace to /home/dwhite/nrfutil/logs/out3.pcapng (2768 bytes)

Output 2:
Error: Failed to decode modem trace: failed to fill whole buffer (error code 100)


I repeated this 3 times. The .pcapng file sizes were 13836 B, 13228 B, 14224 B

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I then attempted to perform a modem trace and output a raw .bin file. The same issue appeared, but the files reached approximately 125 KB each.

Command:
sudo nrfutil trace lte --input-serialport "/dev/ttyUSB0" --output-raw ~/nrfutil/logs/out3.bin

Output 1:
Saving trace to /home/dwhite/nrfutil/logs/out3.bin (15360 bytes)

Output 2:
Error: Failed to decode modem trace: failed to fill whole buffer (error code 100)


The .bin file sizes were 112640 B, 137216 B, 126976 B

Why is this happening, and how can I fix this issue?

[Devon W]

Update (no solution yet):

I ran a modem trace on my Windows machine to investigate further. After the command AT+VZWAPNE? is sent by my device, my device receives this packet:

Rcvd AT Command: +VZWAPNE: 2,"VZWADMIN","IPV4V6","LTE","Enabled"  +VZWAPNE: 3,"VZWINTERNET","IPV4V6","LTE","Enabled"  +VZWAPNE: 4,"VZWAPP","IPV4V6","LTE","Enabled"  +VZWAPNE: 6,"VZWCLASS6","IPV4V6","LTE","Enabled"  +VZWAPNE: 7,"VZWIOTTS","IPV4V6","LTE","Enabled"  +VZWAPNE:  

This packet is 269 bytes long. It also happens to be the ONLY packet that exceeds 256 bytes. The next largest packet is 255 bytes.

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Hypothesis: nRFUtil's trace program does not allocate enough memory for the buffer/variable storing incoming packets.

[Øyvind]

Hello, and thanks for your patience with this issue. 

I'm not familiar with the AT command VZWAPNE. Could you please elaborate more on this command i.e. is this something you have added to your Serial LTE Modem? Can you share the pcapng files? 

Are you able to collect modem trace with running AT Client on your device?

Devon W said:

I ran a modem trace on my Windows machine to investigate further.

Are you able to share the modem trace file from the Windows machine? Did you use nrfutil on the Windows machine as well? Is it possible for you to test with the Cellular Monitor app in nRF Connect for Desktop?

Thanks!

Kind regards,
Øyvind

[Devon W]

Øyvind said:

I'm not familiar with the AT command VZWAPNE

VZWAPNE is a Verizon-specific command. Other Verizon AT-Commands work fine, it is just this one that breaks the buffer in the nrfutil trace utility.

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Øyvind said:

Are you able to share the modem trace file from the Windows machine?

I can, but only if this ticket is made private.

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Øyvind said:

Did you use nrfutil on the Windows machine as well?

I did not, but I will try doing that.

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Øyvind said:

Is it possible for you to test with the Cellular Monitor app in nRF Connect for Desktop?

I tested this with the Cellular Monitor App, and had no issues.