libraries/PDM/src/PDM.cpp: Add PDM begin and end.

[Rathan25]

PR Description.

1. Added PDM.begin(), Which dose initialization of PDM, enables channels, configures sample rate.
2. Added PDM.end(), which disables PDM and clear the FIFOs.
3. In example added Basic test on begin() and end().

Done unit test with channels and passing sample rate. For single channel it configures with left channel . Going forward need to check with application

Captured logs:

[ederjc]

Please complete the work or open against a feature branch.
Also, make sure the checks are passing.

[jaenrig-ifx]

Good start 👍
We have to also start thinking of the tests in arduino-core-test
In micropython we have faked a pcm signal with gpio toggling and then read the pattern from the receiver:
https://github.com/Infineon/micropython/blob/ports-psoc6-main/tests/ports/psoc6/board_ext_hw/multi/pdm_pcm_rx.py
https://github.com/Infineon/micropython/blob/ports-psoc6-main/tests/ports/psoc6/board_ext_hw/multi/pdm_pcm_tx.py

[jaenrig-ifx]

As we are going to be able to create multiple instances, this should be a data type -> KEYWORD1

[jaenrig-ifx]

We should create a constructor which accepts the pins, like ->
https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.h#L17*
Then we can have a pre-instantiated object like this:
https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.cpp#L236-L241
And those defines are part of the pins_arduino.h -> https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.cpp#L236-L241

[jaenrig-ifx]

As discussed, there are few more things that need to be taken care in the begin:

• irq setup
• dma
• ringbuffer usage (there is a coreAPI ringbuffer that maybe can be used -> https://github.com/arduino/ArduinoCore-API/blob/master/api/RingBuffer.h
• The clock also needs to be setup depending on the sampling rate.
  https://github.com/Infineon/micropython/blob/ports-psoc6-main/ports/psoc6/machine_pdm_pcm.c#L435-L499
  It is fine, you can gradually add that in subsequent PR.

[jaenrig-ifx]

These defines can be private, in the .cpp?

[jaenrig-ifx]

I would name it PDMClass, as here -> https://github.com/arduino/ArduinoCore-mbed/blob/main/libraries/PDM/src/PDM.h