How to use a UART instead of CDC ACM in Openthread CLI example

[kaushalyasat]

Hi, I am using a third party module based on nRF52840. I want to use a standard UART to operate the CLI shell. I am not clear how to do this, any help?

Thanks,

Kaushalya

[kaushalyasat]

Hi, I have removed the overlay_usb.conf from the Kconfig fragments. I need to find how the UART is specified to trace which pins are  Tx and RX. I searched for a reference of PSEL.TXD anywhere in the project, but I couldnt find any. Really need some help here.

Thanks,

[AHaug]

Hi,

Could you give me some more information about your project:

1. What SDK are you using?
2. Are you basing your application on any existing Nordic Semiconductor firmware samples?
   1. Have you had a look at https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/openthread/cli/README.html? The Thread CLI sample supports UART and USB CDC ACM as serial transports. By default, it uses UART transport. To switch to USB transport, activate the USB overlay extension.

Kind regards,
Andreas

[kaushalyasat]

Thanks Andreas,

1. SDK 2.0.0

2. Yes this is the /OpenThread/CLI sample

a. Yes I have. I am not using the overlay_usb.conf, so my assumption is the build should be using the default UART as the transport layer. Now the question is to find how the UART is mapped or which external pins are associated with the default UART. I am using nrf52840dk_nrf52840.dts, so I guess the uart0 is the one used based on

	chosen {
		zephyr,console = &uart0;
		zephyr,shell-uart = &uart0;
		zephyr,uart-mcumgr = &uart0;
		zephyr,bt-mon-uart = &uart0;
		zephyr,bt-c2h-uart = &uart0;
		zephyr,sram = &sram0;
		zephyr,flash = &flash0;
		zephyr,code-partition = &slot0_partition;
	};

Now further below the DTS, I see

&uart0 {
	compatible = "nordic,nrf-uarte";
	status = "okay";
	current-speed = <115200>;
	pinctrl-0 = <&uart0_default>;
	pinctrl-1 = <&uart0_sleep>;
	pinctrl-names = "default", "sleep";
};

I cant find where 'uart0_default' is defined.

Thanks,

Kaushalya

[kaushalyasat]

Also at add to my previous comment, by looking at resources list in my project, I can see UART0 Tx is GPIO0.6 and RX is GPIO0.8. I can see when I measure the voltage of these, they are both at 3V (VDD). Unfortunately I dont see any response once I hooked up a USB to TTL cable (3V3) to these ports. This may mean still the project is configured for USB transport layer. How can we verify which transport the project is configured to?

Thanks,

[kaushalyasat]

Hi Andreas,

I've been debugging into this and have some interesting results.

1. I programed the on-board CPU on the Dev Kit and I could see the UART working from P0.6 and P0.8. So this means project is build correctly with UART as the transport layer.

2. Then to test the UART connection on my third party module, I build the 'getchar' example project and programmed my module with it. Then the UART was working with P0.6(TX) and P0.8(RX). I built both projects with NRF52840DK_NRF52840.dts file.

Conclusions

Based on 1. The OpenThread CLI project is built with UART as the transport layer.

Based on 2. My third party module's UART and wiring is working as expected.

So the question now is why the CLI project programmed to my module doesnt work??

Any ideas?

Thanks,