SAMD51 I2C slave support for Wire library and SAMD51 viariants.

[JordanMajd]

Fixes #45 by adding handlers for all for SAMD51 SERCOM I2C interrupts to wire.cpp and defining them in the appropriate variant.h.

This is opened as a draft, because the M4 Trellis has a conflict as it already defined handlers for SERCOM4 for use with UART Serial1 in its variants.cpp. I'm looking for advice on how to best resolve this.

[ladyada]

thank you this is great! i think trellis is the tough one because its a multi-use port

however i think lets keep it for Serial use ... that way it can be used with MIDI which our demos show off. rather than I2C

sound OK?

[ladyada]

looks good to me - let me know when the PR is ready for review / merge

[JordanMajd]

Serial1 is back online, should be ready for review.

Keep kicking ass, you are an inspiration.

[ladyada]

oh one more request, is there an example you used in Wire library to test? if it isnt already there please add the test sketch!

[JordanMajd]

Tested with existing examples connected to an Uno running the corresponding master/slave example:

• slave_receiver, slave_sender to verify I2C slave operations.
• master_writer, master_reader to verify I2C existing master functionality.

Additionally tested slave_sender against a Pi CM3 running i2cdetect -y <bus> <address> and i2cget -y <bus> <address>

[JordanMajd]

In addition to the above, I was only able to extensively test on an ItsyBitsy M4 and the Trellis M4 when Serial1 was disabled. Definitely worth testing on other hardware.

[ladyada]

tested a feather m4 successfully - you're a hero @JordanMajd :)

[ladyada]

@JordanMajd hi please take a look at https://forums.adafruit.com/viewtopic.php?f=62&t=159769 if you have any suggestions for this person!

[JordanMajd]

rolls d20

Yep, I'll look into it tonight.

[ladyada]

:D thank u!