applications: slm: Fix HWFC problems on nRF9151DK

[SeppoTakalo]

Fix HWFC problems on nRF9151DK

nRF9151DK has interface chip that automatically detects if flow
control is enabled or not. On start up, HWFC pins are floating.

On Zephyr DTS side, nRF9151 CTS pin has pull-up enabled, so if
nRF91 app core boots faster than interface chip, the serial port
might be blocked because of flow control.

Change pull-up to pull-down so nRF91 is allowed to write if interface
chip still has not enabled the HWFC pins.

Drop AT responsed to closed DLCI

If DLCI channel for AT commands has been closed, avoid sending
data to the pipe.

Channel is resumed once remote end connects to the DLCI channel.

[NordicBuilder]

CI Information

^{To view the history of this post, clich the 'edited' button above}
Build number: 3

Inputs:

Sources:

sdk-nrf: PR head: ac0b78d7d9358a6e8e9585cbcff73533e592762b

more details

sdk-nrf:

PR head: ac0b78d7d9358a6e8e9585cbcff73533e592762b
merge base: 4c623e64e60633b234c20150d040be7e560c5b50
target head (main): 4c623e64e60633b234c20150d040be7e560c5b50
Diff

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 (4)

applications
│  ├── serial_lte_modem
│  │  ├── Kconfig
│  │  ├── overlay-cmux.conf
│  │  ├── src
│  │  │  ├── slm_at_host.c
│  │  │  │ slm_cmux.c

Outputs:

Toolchain

Version: 4ffa2202d5
Build docker image: docker-dtr.nordicsemi.no/sw-production/ncs-build:4ffa2202d5_e579f9fbe6

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

• ◻️ Toolchain - Skipped: existing toolchain is used
• ✅ Build twister
  • sdk-nrf test count: 30
• ✅ Integration tests
  • ✅ test-fw-nrfconnect-nrf-iot_serial_lte_modem

Disabled integration tests

• • desktop52_verification
  • doc-internal
  • test-fw-nrfconnect-apps
  • test-fw-nrfconnect-ble_mesh
  • test-fw-nrfconnect-ble_samples
  • test-fw-nrfconnect-boot
  • test-fw-nrfconnect-chip
  • test-fw-nrfconnect-fem
  • test-fw-nrfconnect-nfc
  • test-fw-nrfconnect-nrf-iot_cloud
  • test-fw-nrfconnect-nrf-iot_libmodem-nrf
  • test-fw-nrfconnect-nrf-iot_mosh
  • test-fw-nrfconnect-nrf-iot_positioning
  • 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-proprietary_esb
  • test-fw-nrfconnect-ps
  • test-fw-nrfconnect-rpc
  • test-fw-nrfconnect-rs
  • test-fw-nrfconnect-tfm
  • test-fw-nrfconnect-thread
  • test-fw-nrfconnect-zigbee
  • test-low-level
  • test-sdk-audio
  • test-sdk-dfu
  • test-sdk-find-my
  • test-sdk-mcuboot
  • test-sdk-pmic-samples
  • test-sdk-sidewalk
  • test-sdk-wifi
  • test-secdom-samples-public

Note: This message is automatically posted and updated by the CI

[github-actions]

You can find the documentation preview for this PR here.

[MarkusLassila]

Removing the ready-message was the key in getting the UART to work properly even when the device is started with the power switch.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud