How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

Øyvind — Wed, 25 Mar 2026 10:31:48 GMT

Hello, I am not aware of any levels needed to be set for GCF Certification tests, but the numbers seem sufficient. If you can collect modem traces correctly, this should correct.

Kind regards,
Øyvind

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

RongLinQin — Fri, 20 Mar 2026 09:05:10 GMT

Hi Øyvind:

Thanks for your help.

We tried modifying the following two configuration options. After increasing TRACE_BACKEND_RTT_BUF_SIZE and TRACE_STACK_SIZE, we can capture logs normally now. Could you help check what values should be set for these two configuration and the MODEM TRACE LEVEL for GCF certification test?

CONFIG_NRF_MODEM_LIB_TRACE_BACKEND_RTT_BUF_SIZE=16384
CONFIG_NRF_MODEM_LIB_TRACE_STACK_SIZE=8192

Thanks!

BRs

Qin, Rong-Lin

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

Øyvind — Thu, 19 Mar 2026 07:43:30 GMT

Hello, I have been asked to follow-up on your ticket while Benjamin is out of office.

Could you please share the logs that you are able to capture? This way we can see if it is sufficient or not.

Thanks.

Kind regards,
Øyvind

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

RongLinQin — Mon, 16 Mar 2026 07:29:04 GMT

Hi Benjamin:

Thanks for your help!

After added the -RTTChannel parameter to the JlinkRTTLogger command, LTE RTT trace log could be captured. Following is the command parameters we used:

JlinkRTTLogger -Device nRF9160_xxAA -If SWD -Speed 4000 -RTTChannel 1 e:\ch1.bin

However, the current speed of capturing jlink RTT is slow, the maximum speed of our board is about 70 KB/s. Capturing logs for a single LTE network attachment operation takes more than ten minutes. Sometimes the captured logs cannot be decoded by wireshark, and we are not sure if this is due to incomplete log capture caused by the slow speed. Could you give us some guidance on optimizing the JLink RTT capture log speed?

thanks.

BRs

Qin, Rong-Lin

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

Benjamin — Wed, 11 Mar 2026 13:05:13 GMT

Hi,
The Cellular Monitor application does not support RTT directly. You will first need to capture the trace as a .log file using the J-Link RTT logger software and then convert it using Cellular Monitor as described here.

Regards,
Benjamin

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

RongLinQin — Tue, 10 Mar 2026 07:18:45 GMT

Hi HungBui:

Thanks for your help!

I tried added these RTT trace configurations in at_client's prj.conf as picture "prj_conf.png". Then build the project and download the "merged.hex" to nRF9160DK. Then use JLinkRTTLogger command to capture modem trace rtt log as picture "rtt_log.png". When I start Cellular Monitor and Refresh dashboard, some AT commands can be seen being sent in the Serial Terminal, but no data is captured by JLinkRTTLogger. Could you help us to check it ?

BRs

Qin, Rong-Lin

RE: How to enable JLINK RTT modem trace for the at_client sample in NCS v3.2.3?

Hung Bui — Mon, 09 Mar 2026 12:22:29 GMT

Hi Ronglin,
Have you followed the guide here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/libraries/modem/nrf_modem_lib/nrf_modem_lib_trace.html#modem_tracing_with_rtt

Or you can use the snippet as described here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/device_guides/nrf91/nrf91_snippet.html#nrf91-modem-trace-rtt-snippet

Basically it's these configurations:

CONFIG_NRF_MODEM_LIB_TRACE=y

# Modem trace RTT backend
CONFIG_NRF_MODEM_LIB_TRACE_BACKEND_RTT=y

# RTT configuration
CONFIG_USE_SEGGER_RTT=y