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samples: bluetooth: central_uart: status LEDs for nRF54LM20 Dongle#27722

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Damian-Nordic:nrf54dongle-leds
Mar 30, 2026
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samples: bluetooth: central_uart: status LEDs for nRF54LM20 Dongle#27722
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Damian-Nordic:nrf54dongle-leds

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@Damian-Nordic Damian-Nordic commented Mar 26, 2026

On nRF54LM20 Dongle, let:

  • green LED indicates BLE connection state and traffic
  • blue LED indicate logging activity.

@Damian-Nordic Damian-Nordic requested review from a team as code owners March 26, 2026 11:54
@NordicBuilder NordicBuilder added the doc-required PR must not be merged without tech writer approval. label Mar 26, 2026
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NordicBuilder commented Mar 26, 2026 •
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Build number: 6

Inputs:

Sources:

sdk-nrf: PR head: 1213d70c67e8285a17f996c773f1a339039dd2f9

more details

sdk-nrf:

PR head: 1213d70c67e8285a17f996c773f1a339039dd2f9
merge base: 8167d2701fc3e29aeb0881f46cc2d2ff9874624f
target head (main): 6e129075406ae55fd9b825e949853ae1e60aaba8
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Github labels

Enabled Name Description
ci-disabled Disable the ci execution
ci-all-test Run all of ci, no test spec filtering will be done
ci-force-downstream Force execution of downstream even if twister fails
ci-run-twister Force run twister
ci-run-zephyr-twister Force run zephyr twister
List of changed files detected by CI (7) 
samples
│  ├── bluetooth
│  │  ├── central_uart
│  │  │  ├── CMakeLists.txt
│  │  │  ├── README.rst
│  │  │  ├── boards
│  │  │  │  ├── nrf54lm20dongle_nrf54lm20b_cpuapp.conf
│  │  │  │  │ nrf54lm20dongle_nrf54lm20b_cpuapp.overlay
│  │  │  ├── src
│  │  │  │  ├── leds.c
│  │  │  │  ├── leds.h
│  │  │  │  │ main.c

Outputs:

Toolchain

Version: 911f4c5c26
Build docker image: docker-dtr.nordicsemi.no/sw-production/ncs-build:911f4c5c26_5ea73affbf

Test Spec & Results: ✅ Success; ❌ Failure; 🟠 Queued; 🟡 Progress; ◻️ Skipped; ⚠️ Quarantine

  • ◻️ Toolchain - Skipped: existing toolchain is used
  • ✅ Build twister - Skipped: Skipping Build & Test as it succeeded in a previous run: 4
  • ✅ Integration tests
    • ⚠️ test-fw-nrfconnect-ble_samples
Disabled integration tests
    • test-fw-nrfconnect-nrf_lrcs_mosh
    • test-fw-nrfconnect-nrf_lrcs_positioning
    • desktop52_verification
    • test_ble_nrf_config
    • test-fw-nrfconnect-apps
    • test-fw-nrfconnect-ble_mesh
    • test-fw-nrfconnect-chip
    • test-fw-nrfconnect-fem
    • test-fw-nrfconnect-nfc
    • test-fw-nrfconnect-nrf-iot_libmodem-nrf
    • test-fw-nrfconnect-nrf-iot_lwm2m
    • test-fw-nrfconnect-nrf-iot_samples
    • test-fw-nrfconnect-nrf-iot_thingy91
    • test-fw-nrfconnect-nrf-iot_zephyr_lwm2m
    • test-fw-nrfconnect-nrf_crypto
    • test-fw-nrfconnect-ps-main
    • test-fw-nrfconnect-rpc
    • test-fw-nrfconnect-rs
    • test-fw-nrfconnect-tfm
    • test-fw-nrfconnect-thread-main
    • test-low-level
    • test-sdk-audio
    • test-sdk-dfu
    • test-sdk-find-my
    • test-sdk-mcuboot
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divipillai
divipillai reviewed Mar 26, 2026
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Comment thread samples/bluetooth/central_uart/README.rst Outdated
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github-actions Bot commented Mar 26, 2026 •
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You can find the documentation preview for this PR here.

Preview links for modified nRF Connect SDK documents:

https://ncsbmdoc.z6.web.core.windows.net/ncs/PR-27722/nrf/releases_and_maturity/releases/release-notes-changelog.html
https://ncsbmdoc.z6.web.core.windows.net/ncs/PR-27722/nrf/samples/bluetooth/central_uart/README.html

ktaborowski
ktaborowski approved these changes Mar 26, 2026
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looks good, minor comment below

Comment thread samples/bluetooth/central_uart/src/leds.c Outdated
*/
static const struct gpio_dt_spec log_led =
GPIO_DT_SPEC_GET(DT_CHOSEN(nordic_central_uart_log_led), gpios);
static int log_led_blink_remaining;
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@ktaborowski ktaborowski Mar 26, 2026

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minor: Type inconsistency between this and ble_led_blink_remaining (is uint8_t)

Comment thread samples/bluetooth/central_uart/src/leds.c Outdated
Comment on lines +34 to +35
k_timer_stop(timer);
gpio_pin_set_dt(&ble_led, 1);
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potential race condition - if leds_set_ble_connected(false) happens between those two, the led stays on, despite the ble is disconnected. I don't know what is the probability of such event (probably very low).
Writing this way it will fix:

gpio_pin_set_dt(&ble_led, ble_connected ? 1 : 0);

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@Damian-Nordic Damian-Nordic Mar 26, 2026 •
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That's why I stop the timer in leds_set_ble_connected so I think there's no such a risk, right? Timer handler is executed from ISR, so it cannot be preempted by a thread.

Comment thread samples/bluetooth/central_uart/src/leds.c
void leds_init(void)
{
if (!gpio_is_ready_dt(&ble_led)) {
return;
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There is no log in this module, also all functions in leds.h are void. Please consider some logging on fails.
Readme says nRF54LM20 Dongle The sample uses the CDC ACM interface with index 0 for debug logging

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Would you like me to check all error codes, such as k_timer_stop, k_timer_start and such or are you interested in specific ones?

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@Damian-Nordic Damian-Nordic Mar 27, 2026

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Added some logs and asserts here and there.

LuDuda
LuDuda approved these changes Mar 26, 2026
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LGTM 👍

@Damian-Nordic
samples: bluetooth: central_uart: status LEDs for nRF54LM20 Dongle
1213d70 
On nRF54LM20 Dongle, let:
- green LED indicates BLE connection state and traffic
- blue LED indicate logging activity.

Signed-off-by: Damian Krolik <damian.krolik@nordicsemi.no>
@Damian-Nordic
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Damian-Nordic commented Mar 27, 2026

@nordicjm Please review

@Damian-Nordic Damian-Nordic added this to the 3.3.0 milestone Mar 27, 2026
@rlubos rlubos merged commit f5124cb into nrfconnect:main Mar 30, 2026
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