Add SPI slave support and basic example
Summary
This PR implements SPI slave mode.
References
This is a follow up for the ticket #1600.
Motivation
Most high level possible functions to implement this feature were used. In order to be as close as possible to other Arduino examples.
SPIClass functions have not been touched as much as possible.
Validation
Example sketches for SPI master and slave are provided with this PR.
Hi, is this actively being worked on? I wanted to use this functionality and am willing to test and co-auth if required.
Hi @ric96 Unfortunately I don't have much time to work on it. Another project is taking all my free time right now. Of course I'm happy with any contributions here
I'd also really like to see this going upstream and I think it'd be worth putting some effort into once for a peace of mind later on, when using it in a project and not having to continuously level local patchsets. How can I help?
Superseded by #2050.