The rp2040 is _very_ marginal for mp3 playback, and currently sometimes triggers a bug that gives garbled audio output. However, it does work for some limited situations.
Any two consecutive pins can be used for an IncrementalEncoder
Testing performed: Put a synthesized (few hundred counts per second) quadrature signal into GP2/3 and read the encoder out. Performed filesystem operations at the same time to stress test it.
The reasons for not using common_hal_rp2pio_statemachine_readinto are commented on.
This adds I2SOut and PDMIn support via PIO.
StateMachines can now:
* read and read while writing
* transfer in 1, 2 or 4 byte increments
* init pins based on expected defaults automatically
* be stopped and restarted
* rxfifo can be cleared and rxstalls detected (good for tracking when
the reading code isn't keeping up)
Fixes#4162
Also found a race condition between timer_disable and redraw, which
would happen if I debugger-paused inside common_hal_rgbmatrix_timer_disable
or put a delay or print inside it. That's what pausing inside reconstruct
fixes.
So that the "right timer" can be chosen, `timer_allocate` now gets the `self`
pointer. It's guaranteed at this point that the pin information is accurate,
so you can e.g., find a PWM unit related to the pins themselves.
This required touching each port to add the parameter even though it's
unused everywhere but raspberrypi.
The RP2040 is new microcontroller from Raspberry Pi that features
two Cortex M0s and eight PIO state machines that are good for
crunching lots of data. It has 264k RAM and a built in UF2
bootloader too.
Datasheet: https://pico.raspberrypi.org/files/rp2040_datasheet.pdf
