UART usage - I cannot see the light in the SDK

[Thomas]

In advance I would like to say I’m sorry for the frustration that this message reflects…Event though I have been using the UART for some time, adding more functionality makes me search documentation for a UART description, and this makes me really frustrated.

I have what I think is a relatively simple need, I want to use UART0 and UART1 on a nRF32840 (both for some RS485 communication).

 

I do not care if it is NRF_DRV, NRFX or APP layer, anything that can be made to work will do!

 

Originally, I thought that selecting between NRF or NRFX was simple; documents suggest that NRF is legacy and I should use the "new" NRFX layer.

So selecting NRFX_UART_ENABLE would be logical and then including nrfx_uart.c driver file.....

But nothing is that simple with this SDK.... there always seems to be a mess of dependencies between configuration macros and files you need to include. and absolutely nothing that documents it (except heavy reading of header files of course ;-). I would love to see. “If you want this layer, tick this in SDK config and include ….”)

Well initial suggestion as above for NRFX just creates a bunch of errors…. so what is the combination needed...

It seems I can choose between using:

1 nrf_drv_uart

2 nrfx_uart

3 nrfx_uarte

4 app_uart

Can anyone suggest settings that will make just one of these options work, it would be highly appreciated and hopefully spare me a lot of testing and experimentation.

What I’m looking for what is a combination of what should be in SDK Config for

NRFX_UARTE section

NRFX_UART section

NRF_DRV (UART_ENABLED) section

APP_UART_ENABLED (+APP_FIFO_ENABLED) section

And any other sections that have dependencies!

I want to be able to call ???_init, send one or more bytes and receive bytes one by one

[Edvin]

Hello,

I understand your frustratsion, as this seems to be quite confusing for a lot of users since we introduced the nrfx drivers. 

First, let me say that there is no choice between legacy and nrfx drivers in the examples in the SDK. I believe some of the old drivers are still present, but you will see that all the examples use the nrfx drivers. Now, the confusing part is that the sdk_config.h file includes both the NRFX and the legacy defines. The reason for this was to make the examples easier to port (backward compatibility), but it has caused a lot of confusion.

You are probably not aware of the file apply_old_config.h, but if you open it, you will see how the different defines are being set. Basically, if the legacy defines are defined, they will overwrite the NRFX_... defines from sdk_config.h. You will however see if you follow the definitions for the driver functions that there is a port layer between the legacy names and the nrfx drivers.

E.g. nrf_drv_uart_init() calls nrfx_uart_init() or nrfx_uarte_init() depending on the NRF_DRV_UART_WITH_UARTE and NRF_DRV_UART_WITH_UART define.

My recommendation is that you set all the NRF_UART defines and the NRFX_UART defines in sdk_config.h equal to each other, and take a look in apply_old_config.h.

There is also an example in the SDK15.3.0\examples\peripheral\serial_uartes that uses both UARTs. You can read about it's description here.

It should also be possible to use the app_uart library, that is used in e.g. the ble_app_uart example, and add another uart. Just set both the legacy and nrfx defines to be the same. If you do this, which I believe that you have tried, what sort of errors do you encounter?

Best regards,

Edvin

[Thomas]

Thank you for the information !

As you can see from my comments, from investigation I found out about the "feature" that you have to define both new NRFX and legacy layer identical. Why not automaticially define legacy if required.

If I, as a new user selects to use the NRFX layer as recommended. Why do I the have to include lagacy layer also if it's just wrapping the new layer. That does seem to be the case. My app does not link without legacy layer included. 

I find NO EXAMPLES using nrfx layer.

I can find examples using APP layer (uart) and just now I found the example using the nrf_serial library (but seems to be using legacy layer) in the serial and serial_uartes examples.

Any information on how to receive an unknown number of characters? I see the info about double buffering, but do not really find any detailed information or examples I can use.