RE: CONFIDENCE & CONFIG Settings

Jim Logsdon — Mon, 25 Aug 2025 18:59:11 GMT

please close this ticket

RE: CONFIDENCE & CONFIG Settings

Jim Logsdon — Thu, 27 Feb 2025 13:49:17 GMT

Thank you

RE: CONFIDENCE & CONFIG Settings

Håkon Alseth — Wed, 19 Feb 2025 15:51:57 GMT

Hi,

For the device that you use, which seems to be a nRF52832, that only has one UART instance, it will automatically select that instance if this is set:

[quote user=""]CONFIG_UART_ASYNC_API=y[/quote]

Then this is default y:

[quote user=""]CONFIG_UART_0_ASYNC=y[/quote]

However, these are not default y:

[quote user=""]

CONFIG_UART_0_NRF_HW_ASYNC=y

CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2

[/quote]

As the first one does not have a default 'y' in its definition:

https://docs.nordicsemi.com/bundle/ncs-latest/page/kconfig/index.html#CONFIG_UART_0_NRF_HW_ASYNC

Nor does the async timer instance:

https://docs.nordicsemi.com/bundle/ncs-latest/page/kconfig/index.html#CONFIG_UART_0_NRF_HW_ASYNC_TIMER

So, why is there multiple configurations here? The problem lies with the NRF_UARTE peripheral itself.

https://docs.nordicsemi.com/bundle/ps_nrf52832/page/uarte.html#d955e183

It does not give you the "on-going" amount of bytes received directly in hardware (nRF54L-series gives this in the UARTE.RX.CURRENTAMOUNT register), so to be able to count the amount of bytes you're receiving, you need to use the byte-for-byte event RXDRDY.

By looking at the configuration for the "_HW_ASYNC" feature, it uses dedicated hardware peripherals (PPI and TIMER instance) to count the incoming bytes as compared to using k_timer instance(s) for timeout.

The UARTE hardware peripheral on nRF52832 will effectively be able to count each incoming byte with the RXDRDY event, and using a TIMER to count + PPI will be more efficient (and accurate) as compared to manually incrementing a byte-counter variable in a ISR.

If you have a TIMER instance available, the best option is to enable:

[quote user=""]

CONFIG_UART_0_NRF_HW_ASYNC=y

CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2

[/quote]

I agree with your conclusion:

[quote user=""]My point is that I'm "guessing" at CONFIG settings, hoping that they are correct. That is not engineering. [/quote]

The choices that you are presented with are not explained properly, which I will bring up internally.

Kind regards,

Håkon