Hey

I done a demo driver implementation:

https://github.com/StefJar/zephyr_stm32_uart3_dma_driver

Some problems I was facing:

- DMA API: the current one doesn't support ring buffer setups

- UART API: the current API is not mapping the IDLE event.

- UART API: no callbacks possible for event driven rx

With the current design of the UART and DMA API it seems to be
challenging to get a nice fusion.

So I was implementing a simple API for the demo, making block writes
possible and calling a callback when data is received. I didn't used the
UART and DMA API because it would became a dirty hack, while calling
functions form that API & overwriting/patching the ISRs. So I decided
for a lean straight forward implementation.

In my case I am interested into SPI + DMA and USB ACM + DMA. From an
energy perspective it is much better to use DMA transfers for the
peripheral IOs (We can put the MCU to sleep).

Maybe it is worth to put a thought on using DMA for peripherals by
default and only the special case is doing polling or RX/TX handling via
uart etc. ISRs.

Stefan

On 20/03/2019 15:37, Paul Sokolovsky wrote:
> Hello Stefan,
>
> On Tue, 19 Mar 2019 15:18:02 +0000
> "Stefan Jaritz" <stefan@...> wrote:
>
>> Hey,
>>
>> I am currently experimenting with ZephyrOS on different tasks. My
>> base is an own dev board which has a stm32f4xx MCU that connects
>> different ICs etc. via UART, I2C, SPI & GPIOs.
>>
>> Currently the UART ISR is too slow to catch all chars at a rx burst.
>> Usually I am using UART + DMA transfers to relieve the MCU and save
>> energy.
>>
> []
>
>> So I am asking for help or some example how to do an UART & DMA.
>>
>> Think having an ringbuffer for rx and an intr firing after n Bytes
>> received via DMA. Also doing the tx via DMA would be perfect. Any
>> ideas to setup the Zephyr drivers to do so?
> Recently, a new "async" UART API was added to Zephyr, whose
> implementation could leverage DMA support (that was one of usecases for
> this API). There's an open ticket to implement it for STM32:
> https://github.com/zephyrproject-rtos/zephyr/issues/13955
>
> You're welcome to cooperate with the STM32 maintainers on implementing
> it.
>
> []
>