nRF9160 SLM with SLM Shell communication issues

RE: nRF9160 SLM with SLM Shell communication issues

JackT — Fri, 13 Jun 2025 08:11:49 GMT

Ok thanks that is clear

In the SLM: Shell sample version latest:

In the SLM: Shell sample version 3.0.1 and earlier:

the SLM itself has always stated for flow control to be enabled. so this was mismatched before. But it also works without.

RE: nRF9160 SLM with SLM Shell communication issues

Øyvind — Fri, 13 Jun 2025 08:03:54 GMT

[quote user="JackT"]Yes, that was it! Many thanks! [/quote]

I'm glad we were able to find the culprit! Happy to help! 🙂

[quote user="JackT"]Is this because of the terminal? [/quote]

No, this is part of the Shell, have a look at this Reddit thread

[quote user="JackT"]Or, if I send commands directly from code, do I need to add these backslashes as well?[/quote]

Yes, have a look at Sending AT Commands in our NCS documentation.

[quote user="JackT"]Also extra question, since in the newer V3.1.0 SLM and SLM Shell both mention with flow control, is this now recommended and maybe in the future required? my setup has no flow control, but does still work.[/quote]

Could you please point me to where this is stated? The nRF9160DK has virtual serial ports that uses Request to Send (RTS)/Clear to Send (CTS)-style Hardware Flow Control (HWFC). This may be the reason it states this, and most likely actually include HWFC in your applications.

Kind regards,
Øyvind

RE: nRF9160 SLM with SLM Shell communication issues

JackT — Fri, 06 Jun 2025 12:24:57 GMT

Yes, that was it! Many thanks! In the screenshot, you can see the first original message and after with the added \. I had a feeling it was something to do with a character, but I couldn't figure out which one. Debugging would have helped me here 😅.

Is this because of the terminal?

Or, if I send commands directly from code, do I need to add these backslashes as well?

And are there any other escape characters I should be wary of?

Also extra question, since in the newer V3.1.0 SLM and SLM Shell both mention with flow control, is this now recommended and maybe in the future required? my setup has no flow control, but does still work.

RE: nRF9160 SLM with SLM Shell communication issues

Øyvind — Fri, 06 Jun 2025 08:49:00 GMT

Hello, and thanks for sharing. I've had some more time to review the issue and this looks like an issue with the escape characters that are needed when sending these commands over UART. This is typical for the misc shell programs i.e. AT#XPING=\"5.189.130.26\",45,5000,5,1000

Could you also include CONFIG_SLM_LOG_LEVEL_DBG=y in your SLM application?

Kind regards,
Øyvind

RE: nRF9160 SLM with SLM Shell communication issues

JackT — Wed, 04 Jun 2025 11:58:47 GMT

I just copied the SLM and SLM shell from the NCSV3.0.1 examples. In the SLM SHell zip is also the nrf54l15 board files that i tried and the nrf53dk should be these orginal.

And yes PC works everytime. Sending from DK results in some commands working (ie. AT+CFUN=1) but others not (i.e. AT+CPSMS=1,,,"00000001","00000011" or AT#XPING)

devzone.nordicsemi.com/.../serial_5F00_lte_5F00_modem_5F00_1.zip devzone.nordicsemi.com/.../slm_5F00_shell.zip

RE: nRF9160 SLM with SLM Shell communication issues

Øyvind — Wed, 04 Jun 2025 10:35:17 GMT

Hello Jack,

Could you share your SLM and SLM shell project for me to reproduce? This is only when sending commands over UART from e.g. nRF5340DK, but not when sending directly to nRF9160DK from PC?

Kind regards,
Øyvind