* Add support for the extra 16 GPIO pins in the menus and core.
* Clean up Generic RP2350 PSRAM ("none" is valid) and flash (other than 16MB) options.
* Add extra GPIO<->peripheral connections
* Add Pimoroni PGA2350 RP2350B-based board
* Pins 32-47 can be used for PIOPrograms
* Avoid hang when PSRAM fails to initialize
* Move libpico to an RP2350B board for SDK (otherwise the SDK drops all GPIOHI support)
The PIO programs that generate tone() and Servo() use the TX FIFO to
receive updates to the period/duty cycle.
The original code would push into the FIFO (potentially blocking the
app if the FIFO was full) and generate at least one cycle of every
value written into the control. Basically, the output would
lag the changes by 1 cycle or more (which could be 20ms+ on Servo).
Fix this by clearing any old, ungrabbed values from the FIFO before
sending a new one to the program. Instead of a FIFO, there is
effectively now just a control register and updates will be immediate.
Update the Siren.ino example with delays because now the tone() calls
will not block and run 10x+ faster.
Fixes#121
Supersedes #185
Redo the PIO program to allow the tone generator on a pin to be updated
without interruption, at waveform boundaries. This allows for things like
sirens or slurs to be implemented simply.
Use an alarm, not the PIO hardware, to manage time-limited tones().
Add a simple siren example.
