In my testing, the feather bluefruit can do 12 voices at 48kHz!
This is a simple case (no LFOs, no ring modulation) so other situations might
require a lower sample rate, fewer voices, or both.
The sound is a little artifacty & low-fi but I think that's down to the speaker
& use of PWM instead of I2S.
In #7497 port_background_task was renamed to port_background_tick
but the actual call site wasn't changed. This meant that it was
no longer called!
Rename more functions from task to tick to make it clearer which is
which.
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.
This 2-in-1 PR started with the goal of support the Bangle.js 2
smartwatch with *no USB*.
* Adds "secure" DFU build support with a committed private key.
* Adds 3-bit color support with one dummy bit for the JDI memory display
* Allows nrf boards to have a board_background_task() run in RUN_BACKGROUND_TASK.
This is needed because the Bangle.js 2 uses the watchdog to reset.
* Renamed port_background_task() to port_background_tick() to indicate it
runs on tick, not RUN_BACKGROUND_TASK.
* Marks serial connected when the display terminal is inited. This means
that safe mode messages show up on the display.
ACep, 7-color epaper displays also pack 3 bits in 4. So, I added that
support as well.
* Adds 3-bit ACeP color support for 7-color e-paper displays. (Not
watch related but similar due to color depth.)
* Allows a refresh sequence instead of a single int command. The 7" ACeP
display requires a data byte for refresh.
* Adds optional delay after resetting the display. The ACeP displays
need this. (Probably to load LUTs from flash.)
* Adds a cleaning phase for ACeP displays before the real refresh.
For both:
* Add dither support to Palette.
* Palette no longer converts colors when set. Instead, it caches
converted colors at each index.
* ColorConverter now caches the last converted color. It should make
conversions faster for repeated colors (not dithering.)
