This update to the PR retains the earlier board rev (with a rename) so
that backward binary compatibility is not lost for the earlier board
revision. The primary name 'vina-d51' is retained for the latest
revision to make it easy for customers to select the proper UF2
download - because the name matches the commercial name.
Details:
Replace bdmicro_vina_d51 with bdmicro_vina_d51_pcb7 (revision 7 of
PCB) with boardfiles unmodified. Add _pcb7 to the workflow build.
Replace bdmicro_vina_d51 boardfile content with latest PCB updates
(revision 10 ov PCB). Add minimal comments in the board files to make
it clear which PCB revision is implemented. Update the USB PID to
reflect an updated board revision.
ESP-01 header renamed to AUX, and expanded to 12 pins from 8
pins. Pins 1-8 still accommodate the ESP-01, with expansion to full
SERCOM 4-pad support to allow for SPI and I2C on that expansion port
with additional GPIO control.
Update pins.c with additional signals provided AUX_1-8, along with
UART, SPI, I2C name usage as aliases to appropriate AUX_1-8
signals. Additionally, add several alternate names specific to several
expansion modules - the ESP-01, and the ATW-01 using the WINC_1500
(SPI) w/interrupt and control needed for the WINC - with assignments
to module pin positions.
Re-work SERCOM assignments to accommodate the above from other parts
of the board, which required moving a SERCOM or two around in order to
accommodate the 4-pad sercom pin mapping on the AUX port.
Built and tested using latest from 'main':
Adafruit CircuitPython 6.2.0-rc.0-70-ga1562430f-dirty on 2021-04-05;
BDMICRO VINA-D51 with samd51n20
After this change, the following program works for me on the MIMXRT1010-EVK:
```python
import pwmio
import board
p = pwmio.PWMOut(board.D13, frequency=1_000_000, variable_frequency=True)
p.duty_cycle = 32868
while True:
pass
```
Querying and varying the duty_cycle and frequency work as well.
The lowest frequency obtainable is about 2kHz; there is an additional
divider which would allow lower PWM frequencies (I think 1kHz is important
for servos?)
Something odd happens with very low duty cycles, such as
```python
>>> p.frequency = 2000
>>> p.duty_cycle = 2
```
instead of a symmetrical waveform, it's asymmetrical. With `duty_cycle=4`,
the effect disappears. The reason for this is probably hidden in the
datasheet, but could affect servos or other things that count pulse
widths.
