In contrast to MidiTrack, this can be controlled from Python code,
turning notes on/off as desired.
Not tested on real HW yet, just the acceptance test based on checking
which notes it thinks are held internally.
a waveform object (array of 'h') can be passed in, replacing the
standard square wave. This waveform must be a 'single cycle waveform'
and some obvious things to pass in are sine, triangle or sawtooth waves,
but you can construct whatever you like.
Otherwise, the following would occur:
* settings.toml is in the process of being written by host computer
* soft-reset begins
* web workflow tries to grab CIRCUITPY_WIFI_SSID, but loops forever
because FAT filesystem is in inconsistent state and file reads error
* settings.toml write by host computer never completes and the filesystem
remains corrupt
* restarting yields a soft-bricked device, because startup reads
CIRCUITPY_WIFI_SSID again
* Enable dcache for OCRAM where the VM heap lives.
* Add CIRCUITPY_SWO_TRACE for pushing program counters out over the
SWO pin via the ITM module in the CPU. Exempt some functions from
instrumentation to reduce traffic and allow inlining.
* Place more functions in ITCM to handle errors using code in RAM-only
and speed up CP.
* Use SET and CLEAR registers for digitalio. The SDK does read, mask
and write.
* Switch to 2MiB reserved for CircuitPython code. Up from 1MiB.
* Run USB interrupts during flash erase and write.
* Allow storage writes from CP if the USB drive is disabled.
* Get perf bench tests running on CircuitPython and increase timeouts
so it works when instrumentation is active.
It now handles deinit, never_reset and sharing tracking. PWM
now runs in the WAIT state as well during a time.sleep().
_reset_ok() was removed because it was called in one spot right
before deinit().
Some PWMOut were also switched to a bitmap for use instead of
reference count. That way init and deinit are idempotent.
Fixes#6589. Fixes#4841. Fixes#4541.
