With nRF Connect SDK, how to I change uart0 to "nRF UART without EasyDMA"?

[ayavilevich]

It was suggested in other cases that it may be more power efficient to use uart without easydma in some cases.

I am using NCS and I see CONFIG_UART_0_NRF_UARTE is defined which suggests I am using uart with EasyDMA.

What is the right way to change configuration to disable easydma for uart?

[Hakon]

Hello,

you can try replacing CONFIG_UART_0_NRF_UARTE with CONFIG_UART_0_NRF_UART.

[ayavilevich]

Replace where? The reference says "(No prompt – not directly user assignable.)" about these config options.

[ayavilevich]

This is for nRF52 series. What are the changes that one can make to to configure UART without easyDMA when using NCS on the nRF52?

[Heidi]

Hi! Håkon is on vacation so I will be taking over this case.

UART with easyDMA is dependent on CONFIG_SERIAL which is enabled in the board folder of the nRF52 devices. 

So to configure UART without, just disable this config by adding CONFIG_SERIAL=n to the prj.conf file of your application.

Best regards,

Heidi

[ayavilevich]

Hi, if I add CONFIG_SERIAL=n to the prj.conf file then it will disable serial/uart for the project. This is not what I am asking about.

What I am trying to do is not to disable serial but make a configuration such that CONFIG_UART_0_NRF_UARTE=n and CONFIG_UART_0_NRF_UART=y (which are not user-configurable entries).

And so that I am using the code in https://github.com/nrfconnect/sdk-zephyr/blob/master/drivers/serial/uart_nrfx_uart.c rather than in https://github.com/nrfconnect/sdk-zephyr/blob/master/drivers/serial/uart_nrfx_uarte.c .

The reason why I am looking to do that is because of power consumption. More information here: https://devzone.nordicsemi.com/f/nordic-q-a/47578/nrf52832-uart-power-consumption .

[Heidi]

Oh, I see. 

Looks like this is set by checking the DeviceTree. So you will need to an overlay file and change the uart0 node so that the compatible property is "nordic,nrf-uart", instead of "nordic,nrf-uarte". 

So add a file <board_name.overlay> with the contents:

&uart0 {
	compatible = "nordic, nrf-uart";
};

[ayavilevich]

Hey,

Thanks, this is what I was looking for.

By adding

&uart0 {
	compatible = "nordic,nrf-uart";
};

(note, must not have space)

to a "nrf52840dk_nrf52840.overlay" file in the project I was able to change the driver for uart0.

Unfortunately this didn't have an effect of changing power consumption like I expected based on other discussions. I will check further.