Now a 'once' and a 'loop' buffer can be specified.
'once' is useful for things like writing a neopixel strip in the background,
if you can guarantee the buffer contents are stable until the write is complete.
'loop' is useful for periodic things, like pwm & servos.
both together are useful for some special cases of pwm/servo, where a
transitional waveform needs to be played for one repetition and then
a new waveform needs to be played after that.
The API is renamed to reflect that it's a more generic 'background'
operation.
There were two main issues with the PWM support.
The first is they would fail to work properly if the board goes
into low power mode, when you do things like: time.sleep(0.25)
Can make partially work with this by turning on the proper flags
in each of the FlexPWMTimer Timers/sub-timers, but this did not
appear to work if for example you have both A and B channels
enabled.
Second main problem is that the code did not work with the X
channel of each timer/sub-timer. It looks like someone had
earlier started support for this, But was not sufficient.
Needed to bypass the SDK code and get it closer to the PJRC code.
That is we set the PWM_CTRL_FULL_MASK, which then uses base->SM[submodule].VAL1 to control
when the timer is reset, so it sets up your cycle/frequency. But then this implies that X channel
which uses 0, 1 has to be handled specially. So for the different channels:
A - Uses VAL2 to turn on (0) and VAL3=duty to turn off
B - Uses VAL4 to turn on (0) and VAL5 to turn off
X - As mentioned above VAL1 turns off, but its set to the timing for freqency. so
VAL0 turns on, so we set it to VAL1 - duty
Renamed the board both name of directory within boards, but also the
name reported board name: board_id -- sparkfun_teensy_micromod
Adafruit CircuitPython 7.3.0-beta.0-10-g2a3eb49da-dirty on 2022-04-10; SparkFun Teensy MicroMod Processor with IMXRT1062DVL6A
While testing out this and the new MicroMod Teensy port, @mjs513
and myself found it desirable to have logical pin names for the
different Serial UART objects. It is a lot easier and clearer
to use and maintain to do something
like: uart4 = busio.UART(board.TX4, board.RX4)
than have to go look up the pin numbers for each board.
