mb2-mic-on: low…high level Rust pin-setting

Bart Massey 2024

This code turns on the MicroBit v2 microphone (and thus its "mic on" LED) at varying levels of abstraction:

• raw: Uses arithmetic and the manual.
• structured: Hooray, subroutines.
• pac: Uses nrf52833-pac.
• hal: Uses nrf52833-hal.
• board: Uses microbit-v2.

All but raw turn the mic back off after about three seconds.

You will need to build the pre-hal code with --release to get the timing right. The delay spin-loop will generate a lot of extra instructions per iteration in debug mode, since it will call an iterator next() method each iteration.

These setup commands will get your Linux box set up to run this stuff. Similar things for other platforms.

Acknowledgments

The excellent Comprehensive Rust used to contain some very similar code.