This implements AudioOut, with known caveats:
* pause/resume are not yet implemented (this is just a bug)
* at best, the sample fidelity is 8 bits (this is a hardware limitation)
Testing performed:
My test system is a Particle Xenon with a PAM8302 op-amp
https://www.adafruit.com/product/2130 and 8-ohm speaker. There's no
analog filtering between the Xenon's PWM pin and the "A+" input of
the amplifier; the "A-" pin is disconnected. It is powered from
VUSB.
I used pin D4, which is *NOT* listed as a low-speed-only pin, but
the code does NOT switch the pin to high drive. This is related to
an open issue for general inability to set drive level for pins
being used by a "special function" on nrf:
https://github.com/adafruit/circuitpython/issues/1270
Nothing about the code I've written should limit the usable pins.
All samples I played were 16-bit, generally monophonic at 11025Hz
and 22050Hz from the Debian LibreOffice package.
When nrf pwm audio is introduced, it will be called `audiopwmio`. To
enable code sharing with the existing (dac-based) `audioio`, factor
the sample and mixer types to `audiocore`.
INCOMPATIBLE CHANGE: Now, `Mixer`, `RawSample` and `WaveFile` must
be imported from `audiocore`, not `audioio`.
This also improves Palette so it stores the original RGB888 colors.
Lastly, it adds I2CDisplay as a display bus to talk over I2C. Particularly
useful for the SSD1306.
Fixes#1828. Fixes#1956
- Add copy-pasteable Arch Linux `arm-none-eabi-gcc` install line similar to Ubuntu example
- Add `arm-none-eabi-newlib` as a required package for Arch
- Reformat Ubuntu and Arch install code-blocks to catch the eye for the impatient
Arch Linux changed their packaging for [arm-none-eabi-gcc](https://www.archlinux.org/packages/community/x86_64/arm-none-eabi-gcc/) by creating [arm-none-eabi-newlib](https://www.archlinux.org/packages/community/any/arm-none-eabi-newlib/) as an optional package. Without it users will get errors about missing header files like:
```
In file included from asf4/samd51/include/samd51j19a.h:49,
from asf4/samd51/include/sam.h:38,
from ./mpconfigport.h:31,
from ../../py/mpconfig.h:45,
from ../../py/emitnx64.c:3:
/usr/lib/gcc/arm-none-eabi/9.1.0/include/stdint.h:9:16: fatal error: stdint.h: No such file or directory
9 | # include_next <stdint.h>
| ^~~~~~~~~~
compilation terminated.
```
I designed this really tiny, minimalist font for use on very small
displays. On uGame it lets one see the whole text that CircuitPython
prints on boot. The characters are 4x6 pixels each, and they are
optimized for legibility (large x-height, right angles, blocky shapes).
It might make sense to also use that font in other boards.
Different operations to the display tree have different costs. Be
aware of these costs when optimizing your code.
* Changing tiles indices in a TileGrid will update an area
covering them all.
* Changing a palette will refresh every object that references it.
* Moving a TileGrid will update both where it was and where it moved to.
* Adding something to a Group will refresh each individual area it
covers.
* Removing things from a Group will refresh one area that covers all
previous locations. (Not separate areas like add.)
* Setting a new top level Group will refresh the entire display.
Only TileGrid moves are optimized for overlap. All other overlaps
cause sending of duplicate pixels.
This also adds flip_x, flip_y and transpose_xy to TileGrid. They
change the direction of the pixels but not the location.
Fixes#1169. Fixes#1705. Fixes#1923.
