Can i Use Ring Buffer from Zephyr in Uart Event Handler?

RE: Can i Use Ring Buffer from Zephyr in Uart Event Handler?

Håkon Alseth — Fri, 12 Nov 2021 09:00:11 GMT

Hi,

[quote user="Rajender"]That means i can use Semaphore lock/ mutex lock also in this Uart event handler right?[/quote]

My apologies, I forgot to mention this initially;

you should be very careful about locking semaphores in interrupts, as you shall always give a timeout that is not K_FOREVER:

https://docs.zephyrproject.org/latest/reference/kernel/synchronization/semaphores.html#c.k_sem_take

If you have multiple functions pushing data to this ring-buffer, you can consider moving logic from the interrupt to a workqueue item instead.

Kind regards,

Håkon

RE: Can i Use Ring Buffer from Zephyr in Uart Event Handler?

Rajender — Fri, 12 Nov 2021 08:51:55 GMT

Hi Hakon,

[quote userid="2115" url="~/f/nordic-q-a/81646/can-i-use-ring-buffer-from-zephyr-in-uart-event-handler/338697#338697"]you guard the function with a mutex or similar, as described in the documentation for the function[/quote]

That means i can use Semaphore lock/ mutex lock also in this Uart event handler right?

Best Regards

Rajender

RE: Can i Use Ring Buffer from Zephyr in Uart Event Handler?

Håkon Alseth — Fri, 12 Nov 2021 08:43:42 GMT

Hi Rajender,

[quote user=""]1. what is the max size of buffer for DMA in UART (i need at least 2048 buffer, so is that possible)?[/quote]

The DMA count is 12 bits, so you can send/receive up to 4095 bytes:

https://infocenter.nordicsemi.com/topic/ps_nrf9160/uarte.html?cp=2_0_0_5_18_8_47#register.TXD.MAXCNT

[quote user=""]2. I want to collect this Uart data in Ring Buffer(zephyr/..../sys/ring_buffer.h), can i directly implement ring_buf_put() in Uart Event Handler?, i have tested and its working fine, but i need confirmation that is it good practice or do we have any work arround?[/quote]

Yes, but you have to ensure that if there's multiple scenarios (ie. different functions) where you put data into the ring buffer, that you guard the function with a mutex or similar, as described in the documentation for the function:

https://docs.zephyrproject.org/latest/reference/data_structures/ring_buffers.html#c.ring_buf_put

[quote user=""]3. can i use k_poll_signal_raise() in envent handler?[/quote]

Yes, it should not be problematic.

Kind regards,

Håkon