Can't enable RTT trace

RE: Can't enable RTT trace

Øyvind — Wed, 03 Sep 2025 08:31:39 GMT

At least the developers are aware. Nothing more we can do there.

RE: Can't enable RTT trace

Eizens — Tue, 02 Sep 2025 14:28:14 GMT

super sorry for late reply, I had some other stuff i needed to jump to. I will continue this when i will get back to this project. Thanks for support, i will check it out later.

RE: Can't enable RTT trace

Achim Kraus — Tue, 02 Sep 2025 09:45:50 GMT

[quote userid="77062" url="~/f/nordic-q-a/123609/can-t-enable-rtt-trace/547436"]west build --board <board_target> -- -D<image_name>_SNIPPET="nrf91-modem-trace-rtt"[/quote]

Yes, that's what's documented. But it leaves you with the question, what the "<image_name>" will be ;-).

The answer may be surprising, because "The name of the default image is the name of the folder it resides is".

RE: Can't enable RTT trace

Øyvind — Tue, 02 Sep 2025 09:35:56 GMT

Thanks for pointing out (and reminding me). Did a quick search in our docs using the AI search tool, and it provided the following answer (not far from your answer)

How do I collect modem traces through RTT?

To collect modem traces through RTT (Real Time Transfer) on an nRF91 Series device, follow these steps:

Enable RTT Trace Backend in Your Application

In your project configuration file (prj.conf), add the following Kconfig options:

CONFIG_NRF_MODEM_LIB_TRACE=y CONFIG_NRF_MODEM_LIB_TRACE_BACKEND_RTT=y CONFIG_USE_SEGGER_RTT=y

Alternatively, you can enable RTT tracing by adding the nrf91-modem-trace-rtt snippet to your build. For example, using west:

west build --board <board_target> -- -D<image_name>_SNIPPET="nrf91-modem-trace-rtt"

Or with CMake:

-D<image_name>_SNIPPET="nrf91-modem-trace-rtt"

nRF91 modem traces with RTT backend using snippets
Build and Program the Firmware

Build your application with the above configuration and flash it to your device.
Capture the Trace Using J-Link RTT Logger

Use the SEGGER J-Link RTT Logger to capture the modem trace. Run the following command (adjust the device and file path as needed):

JLinkRTTLogger -Device NRF9160_XXAA -If SWD -Speed 50000 -RTTChannel 1 modem_trace.bin

This will save the raw modem trace data to modem_trace.bin How to capture nrf9160 modem traces using RTT?.
Convert the Trace to PCAP Format (Optional)

You can convert the captured .bin file to PCAP format for analysis in Wireshark using the Cellular Monitor app or nrfutil:

nrfutil trace lte --input-file modem_trace.bin --output-pcapng rtt-trace.pcapng

Asset Tracker Template: Modem Tracing
View the Trace
- Open the .bin or .pcapng file in the Cellular Monitor app or Wireshark for analysis.
- Note: In the current release, Cellular Monitor does not support live RTT capture, but you can load and view previously captured RTT traces Viewing RTT traces in Cellular Monitor.

Summary:
Enable RTT tracing in your firmware, capture the trace with J-Link RTT Logger, and analyze the trace using Cellular Monitor or Wireshark. This method is especially useful if your hardware does not have a spare UART for trace output.

If you need to capture both application logs and modem traces over RTT simultaneously, use different RTT channels for each and capture them in separate terminals Asset Tracker Template: Modem Tracing.

RE: Can't enable RTT trace

Achim Kraus — Fri, 29 Aug 2025 14:46:51 GMT

Finally I found, why the modem trace via RTT failed in the other ticket.

Assuming to enable the snippet with

west build -S nrf91-modem-trace-rtt

the pain will be, that the snippet is applied to all images including McuBoot, and so it fails in the end.

Using

west build -- -D<app>_SNIPPET="nrf91-modem-trace-rtt"

(with the name of the application folder as <app> )

it "works on my machine" ;-).

RE: Can't enable RTT trace

Øyvind — Wed, 13 Aug 2025 07:31:08 GMT

Eizens were you able to test with the GUI on your Mac?

RE: Can't enable RTT trace

Øyvind — Wed, 13 Aug 2025 07:30:10 GMT

Understood! Thanks for pointing out this potential issue. I have it on my list to test and verify 👍

RE: Can't enable RTT trace

Achim Kraus — Wed, 13 Aug 2025 05:23:24 GMT

That other ticket isn't mine, I just retested it for the author of that other ticket. I don't plan to use the modem trace via RTT. I just remembered that other ticket when reading this one.

RE: Can't enable RTT trace

Øyvind — Tue, 12 Aug 2025 13:38:12 GMT

Thanks for pointing out! Will try to test on my side. Could you please register a ticket for this issue? This way we can easily track issues like that.

RE: Can't enable RTT trace

Achim Kraus — Tue, 12 Aug 2025 09:53:59 GMT

OK, the other ticket was about 2.9.0/2.9.2.

RE: Can't enable RTT trace

Øyvind — Tue, 12 Aug 2025 09:47:52 GMT

In this case I tested with the version as the customer, using NCS v2.5.0,

RE: Can't enable RTT trace

Achim Kraus — Tue, 12 Aug 2025 09:45:41 GMT

SDK NCS 2.5.0? Or 2.9.2? Or ... ?

RE: Can't enable RTT trace

Øyvind — Tue, 12 Aug 2025 07:17:17 GMT

Yes, I just did, hence my last answer. From my side the RTT logging works as intended with the settings above.

Kind regards,
Øyvind

RE: Can't enable RTT trace

Achim Kraus — Tue, 12 Aug 2025 06:33:05 GMT

Also other tickets seems to report, that the modem trace via RTT is broken.

Maybe time, that someone from the Nordic team retests the modem trace via RTT?

RE: Can't enable RTT trace

Øyvind — Tue, 12 Aug 2025 06:03:28 GMT

Just out of curiosity, are you able to connect to the board using the GUI application JLinkRTTViewer? From the Logging menu you can "Start Data Logging" which should give the same results. Starting the logging will generate a file with .log ending. This file can be renamed to .bin and opened with the Cellular Monitor to be viewed. Let me know how that works for you.

Here is an example from my log.bin, where I converted the .log to .bin and opened through Load trace file. You can also open the trace in Wireshark.

Kind regards,

Øyvind

RE: Can't enable RTT trace

Eizens — Mon, 11 Aug 2025 12:07:11 GMT

Hi,
The file is not generated.

Modem firmware is 1.3.7, and for test I was using nrf9160 DK. SKD version is 2.5.0.

RE: Can't enable RTT trace

Øyvind — Mon, 11 Aug 2025 11:53:08 GMT

Hello,

Does the modemtraces.bin expand in size? Is it generated at all?

What modem FW are you running on the nRF9160, and are you using custom HW or our development kit? What version of nRF Connect SDK are you using to compile the UDP sample?

Thanks.

Kind regards,
Øyvind