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

[Nguyen Hoan Hoang]

Try this library instead. It's a lot easier to use and more performance. 

https://github.com/IOsonata/IOsonata/blob/master/ARM/Nordic/src/uart_nrf5x.cpp

usage example

https://github.com/IOsonata/IOsonata/tree/master/exemples/uart

performance comparaison from this post : https://devzone.nordicsemi.com/f/nordic-q-a/53106/uart-communication-fifo-error/214454#214454

blog post using uart over BLE the easy way.

embeddedsoftdev.blogspot.com/.../bluetooth-le-with-nordic-nrf51-nrf52.html

[Thomas]

Thank you very much for the suggestion.

I have downloaded the library and made a fast try. I run into some rather difficult things that does not seem easily solvable. I am using Keil uVision.

The library looks quite promising but also has a lot of dependencies. It seems to be depending on GCC that was easily fixed by a pragma (Keil or ARM compiler does not allow anonymous structures).

Secondly it uses some features that are later than C99, not exactly sure. But I am stuck with ARM compiler version 5 that does not support it (atomic). ARM compiler 6 has been around for a long time but seems the rest of the nRF SDK is not compatible with that, so I need to stay on version 5.

[Thomas]

Looking into the problems.

I found a bug in uart_nrf5x.cpp code. Line 434 array index is out of bounds. Array has 16 elements 0..15 and the index used is 16 (the count).

(hope it ok i just report it here)

[Nguyen Hoan Hoang]

It is fixed, thanks for reporting.

[Nguyen Hoan Hoang]

I just committed fixes for some compile issue with Keil CLANG 6.  I use uVision5 and select compiler version 6. 

I finally figured out how uVision5 works.  Can create library project now.  

So far used CrossWorks, SES, IAR, uVision and still find Eclipse is the best and most flexible and above all totally free.  SES is worst, not recommended for real serious work.

[Thomas]

Unfortunately it is not really an option for me at this point. There seems to be conflicts with the nRF SDK code and I am unable to take the time to solve it. (the uart code looks really effective though).

Removing all nRF uart stuff will still give linking problems because of nrfx_prc.c doing the interrupt handling. I cannot remove it as it also handles twi that I am using. 

So it more a matter of resources right now, and existing codebase.

So struck back to start again :-(

[Nguyen Hoan Hoang]

I used it with the SDK no problem.  uart interrupt is independent.  It should not interfere with i2c.  Only i2c & spi have shared interrupt.  Just make sure you disable uart in the sdk_config.h

I looked at the nrf_prs.c, not really useful.  You can just disable it and everything still work fine.  embedded system is not a PC.  We know what are the io map we use.  There no sharing switch between them and the firmware is not an App that you load at runtime neither.  I really don't see the usefulness of that file.