Trying to use UART2 witn custom nrf9151 board non secure

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Wed, 27 Aug 2025 00:45:08 GMT

To be complete, CONFIG_UART_2_INTERRUPT_DRIVEN must also be disabled --per your earlier suggestion!

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Wed, 27 Aug 2025 00:34:01 GMT

OK, with both CONFIG_UART_ASYNC_API=y and CONFIG_UART_2_ASYNC=y enabled,

removed CONFIG_AT_HOST_LIBRARY=y from my demo project

--which did not seem to impact modem communication over UART2

Now Shell commands are working on the default console / UART0

Thank you

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Tue, 26 Aug 2025 21:37:27 GMT

OK, I think I found the culprit

It seems to

CONFIG_AT_HOST_LIBRARY=y

I will run more tests to confirm...

Thanks,

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Tue, 26 Aug 2025 16:50:53 GMT

OK, after restoring both configuration,

the callback set works, and the UART2 communication works as well

However, the shell / help command on the main console / uart0 does not seem to work

Did I miss another configuration?

Thanks,

CONFIG_UART_ASYNC_API=y
CONFIG_UART_2_ASYNC=y

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Tue, 26 Aug 2025 16:03:29 GMT

-ENOTSUP (-134) is returned when CONFIG_UART_ASYNC_API is not enabled.

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Tue, 26 Aug 2025 15:57:49 GMT

Hello Vidar,

I tried your suggestion for the UART configuration, here is my complete prj.conf content

it seems the CONFIG_UART_2_ASYNC is getting forced to n despite being set to y

# CONFIG_UART_ASYNC_API=y
CONFIG_UART_2_ASYNC=y
CONFIG_UART_2_INTERRUPT_DRIVEN=n
# CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_UART_USE_RUNTIME_CONFIGURE=y

# Modem library
CONFIG_NRF_MODEM_LIB=y
CONFIG_AT_MONITOR=y
CONFIG_LTE_LINK_CONTROL=y
CONFIG_AT_HOST_LIBRARY=y

# Enable debug and assertions.
CONFIG_DEBUG=y
CONFIG_ASSERT=y

# Logging configurations.
CONFIG_LOG=y
CONFIG_LOG_MODE_IMMEDIATE=y
CONFIG_LOG_BACKEND_SHOW_COLOR=y
CONFIG_LOG_INFO_COLOR_GREEN=y

# Shell and console support.
CONFIG_SHELL=y
CONFIG_SHELL_LOG_LEVEL_INF=y
CONFIG_SHELL_STACK_SIZE=3072

still getting a failure on the uart_callback_set call, although the error code is -134 instead of -88

[00:00:00.732,635] <inf> main: uart_configure (0)
[00:00:00.738,037] <err> main: uart_callback_set (-134)

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Mon, 25 Aug 2025 13:05:45 GMT

Hi Vidar,

Re: I was able to enable CONFIG_UART_2_ASYNC with CONFIG_SHLL=y if I also disabled CONFIG_UART_2_INTERRUPT_DRIVEN. Did you try the same?

I will give that a try and let you know shortly...

As a matter of fact, I encountered a very similar situation on the Serial LTE Modem (SLM) application

So I will try it there as well...

Thanks

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Mon, 25 Aug 2025 10:25:26 GMT

I was able to enable CONFIG_UART_2_ASYNC with CONFIG_SHLL=y if I also disabled CONFIG_UART_2_INTERRUPT_DRIVEN. Did you try the same?

[quote user="Jamal_nRF"]With that I had to trade uart_set_callback() --which seems to be only supported for ASYNC API???[/quote]

Yes, you're right. Please refer to the "UART async driver API" documentation which describes the difference between these.

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Fri, 22 Aug 2025 20:21:31 GMT

Hi Vidar,

thanks for the additional feedback

I have been able to resolve the problem by using enabling the Interrupt-driven API

Here is how my prj.conf file looks now

CONFIG_UART_ASYNC_API=y
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_UART_USE_RUNTIME_CONFIGURE=y

With that I had to trade uart_set_callback() --which seems to be only supported for ASYNC API???

for uart_irq_callback_user_data_set() –using the callback from the echo_bot zephyr sample

All is good now: I can have both RX/TX traffic on UART2 while supporting Shell commands on the uart0/console.

Thanks again for your support

Jamal

I still don't understand why the SHELL component disables the uart Async API??? But this is not blocking anymore

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Thu, 21 Aug 2025 13:52:06 GMT

Hi,

I've not investigated why enabling CONFIG_SHELL is affects this configuration. However, you should be seeing a Kconfig warning in the build log saying why CONFIG_UART_2_ASYNC does not end up being selected (I'm assuming it is not set in the .config since it's not working). Try to also add the line below and see if that fixes it.

CONFIG_UART_2_INTERRUPT_DRIVEN=n

CONFIG_UART_2_ASYNC=y

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Wed, 20 Aug 2025 19:34:06 GMT

Hi Vidar,

I had this config already enabled

CONFIG_UART_ASYNC_API=y

and now added

CONFIG_UART_2_ASYNC=y

However the latter seems to be forced disabled in the build as I cannot find it in the generated .config file as you indicated.

Please remember my demo app works fine on UART2, with no error when setting the callback

ret = uart_callback_set(uart, uart_cb, NULL);

as long as I keep the CONFIG_SHELL off.

My test goal is keep the UART2 interface working while also adding support for SHELL commands on the UART0/console

Thank you

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Wed, 20 Aug 2025 16:38:45 GMT

Hi,

-88 (-ENOSYS) indicates that the UART async driver API is not enabled, at least not for this UARTE instance. Please try adding CONFIG_UART_2_ASYNC=y to your prj.conf and watch the build output for any errors/warnings, and if not, see if you still get this runtime warning.

Note that you can also check your current configuration from the generated .config in your build output.

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Wed, 20 Aug 2025 16:14:40 GMT

Hi Vidar,

Follow up question if I may keep using this ticket --can open a new one otherwise...

The reason I switched to UART2 was to extend support to SHELL commands using the default console on uart0 (as defined in the nRF9151DK board device tree)

To that end, I enable the SHELL support adding this single line the prj.conf file

CONFIG_SHELL=y

Once I do that, the call to add the uart callback return an error -88

<err> main: uart_callback_set (-88)

The call to enable the call is the same

Is this a known problem on the nRF9151?

Is there a workaround?

How to support SHELL command on the uart0/console while keeping the uart2 peripheral working

Thank you

   ret = uart_callback_set(uart, uart_cb, NULL);
   if (ret)
   {
      LOG_ERR("uart_callback_set (%d)", ret);
      return 4;
   }

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Wed, 20 Aug 2025 16:01:45 GMT

Good to hear you found the problem. Thanks for the update.

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Wed, 20 Aug 2025 15:45:30 GMT

Hi Vidar,

Thank you for confirming my overlay configuration and the pin availability

Regarding the serial bridge, that was indeed my problem. I was using an old Schmart board.

I just switched to an FTDI cable, wired the RX/TX/GND on the arduino heade.

UART2 is working fine now, both TX and RX.

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Wed, 20 Aug 2025 12:31:51 GMT

Hi,

Both pins appear to be available on the DK. As a test, have you tried swapping the TX and RX pins (the TX/RX assignment in nrf9151dk_nrf9151_ns.overlay as well as the physical connections)? Would be interesting to know if RX still works after this.

Also, what is the uart connected to, is it another board, or a usb serial bridge?

RE: Trying to use UART2 witn custom nrf9151 board non secure

Jamal_nRF — Tue, 19 Aug 2025 13:07:47 GMT

Hi Vidar,

I have a related problem using UART2

I kept UART0 as the default for the console on the first serial port

Then configured UART2 out of the arduino header to experiment with the UART peripheral as described this devAcademy course, using a second serial port

https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-4-serial-communication-uart/

The RX interface on UART2 is working as expected, meaning I can toggle the LEDS by sending 1/2/3 characters on UART2/second serial port.

However I cannot get the uart_tx data to write data on the second serial port

All works well with the uart peripheral configured to UART0

To configure UART2, I added this overlay file

nrf9151dk_nrf9151_ns.overlay

content

&pinctrl {
   uart2_default: uart2_default {
      group1 {
         psels = <NRF_PSEL(UART_TX, 0, 23)>;
      };
      group2 {
         psels = <NRF_PSEL(UART_RX, 0, 24)>;
         bias-pull-up;
      };
   };

   uart2_sleep: uart2_sleep {
      group1 {
         psels = <NRF_PSEL(UART_TX, 0, 23)>, <NRF_PSEL(UART_RX, 0, 24)>;
         low-power-enable;
      };
   };
};

&uart2 {
   compatible = "nordic,nrf-uarte";
   status = "okay";
   current-speed = <115200>;
   pinctrl-0 = <&uart2_default>;
   pinctrl-1 = <&uart2_sleep>;
   pinctrl-names = "default", "sleep";
};

RE: Trying to use UART2 witn custom nrf9151 board non secure

Vidar Berg — Tue, 15 Jul 2025 07:33:59 GMT

Hello,

I noticed in your code that the RX timeout is only set to 100 us which is too short and may lead to unreliable reception. Please try to set it to 50 milliseconds and see if that fixes the problem.

#define RX_TIMEOUT (50 * USEC_PER_MSEC)

Best regards,

Vidar