This is a big change: apart from removing LLVM 14 it also removes typed
pointer support (which was only fully supported in LLVM up to version
14). This removes about 200 lines of code, but more importantly removes
a ton of special cases for LLVM 14.
This is just support for the chip, no boards are currently supported.
However, you can use this target on a custom board.
Notes:
- This required a new runtime and machine implementation, because the
hardware is actually very different (and much nicer than older
AVRs!).
- I had to update gen-device-avr to support this chip. This also
affects the generated output of other AVRs, but I checked all chips
we support and there shouldn't be any backwards incompatible
changes.
- I did not implement peripherals like UART, I2C, SPI, etc because I
don't need them. That is left to do in the future.
You can flash these chips with only a UART and a 1kOhm resistor, which
is really nice (no special hardware needed). Here is the program I've
used for this purpose: https://pypi.org/project/pymcuprog/
