add missing XCK definitions for USART SPI

[jayzakk]

We are missing definitions for USART-as-SPI, which I was playing around with.

These are usually coming from avr-gcc mcu header files, but - as we know - in using the 328p files we are missing some functions and definitions ^^

I used the ones from iom324pa.h (as the most "identical" mcu) and changed accordingly.

[dbuezas]

You are really taking every bit ot this board apart! 🎉
Can you also put your code (your "playing around" sketch) in the examples folder?

[jayzakk]

At the moment, it got a rather "large" play code -> https://github.com/jayzakk/lgt8f-tests/blob/master/spitest-lgt8f/spitest-lgt8f.ino
Where I even did not need the XCK, as I just wanted to abuse the SPI for LEDs ^^

But I can build up some test code for whatever "real" SPI device I have around here,

[jayzakk]

There already is a sample sketch around: SPI_UART, which can be used used with simple defines at the nRF24L01 library.

It's "only" missing correct clock selection (it always assumes 16MHz sysclock) and a possibility to switch pins D0/D1 to alternate D5/D6 (only possible at LGT8F). As of now, could not even used as a replacement for SPI.h, as it's missing all the "new" functions (begin/endTransactions, SPISettings(), ...) and only the long-time-obsoleted ones.

Maybe time to write an replacement for that and include some own SPI_UART as SPI.h companion by default?

It just happened that I ordered a couple of those nrf24 modules two days ago ^^

[jayzakk]

@dbuezas, could we merge the two relevant files from https://github.com/jayzakk/spi-uart-test to core?
If yes, I'd like to create a PR.

[dbuezas]

So this should be merged before?
#45

[jayzakk]

If you merge, would be perfect, though it shows conflicts now

[dbuezas]

Can you fix them so I can merge this 🙏 :)

[dbuezas]

hey @jayzakk !
I'd love to merge this one, the conflict looks harmless, can you patch it? :)

[jayzakk]

Huh, I never used that web resolve thing. Guess it's ok now :-/

[LaZsolt]

@jayzakk

Huh, I never used that web resolve thing. Guess it's ok now :-/

Wasn't fully success that web resolve thing. I deleted that macros which was defined twice. #122 (comment)

[jayzakk]

Thanks @LaZsolt
I won't use that anymore ^^