RP2040 and SAMD51:
- Detect when DMA has finished, and stop DMA audio explicitly.
- Do not accidentally reuse `first_buffer` supplied by WaveFile or RawSample. Always realloc `first_buffer` and `second_buffer`
RP2040:
- When audio playing is stopped, write a final zero to the output register. This prevents residual PWM tones.
- Handle buffer size for 8-bit samples properly for 16-bit output.
- Fail on some edge cases (which may not be possible at the moment).
Dan Halbert
microDev
Scott Shawcroft