ESP32S2: Add Readme

[hierophect]

This PR adds a Readme to the ESP32-S2 port, containing information on how to connect, build, flash and debug ESP32-S2 development boards.

Added partially as an extension to #3392, since the configuration files for OpenOCD are presumably GPL and can't be included in the port, so I've documented how to find and modify them yourself. Also includes notes about flashing on Mac OSX figured out by folks on the discord.

[jerryneedell]

Looks good! Thanks. I have not tried the OCD configuration myself. Looking forward to trying it.

[hierophect]

(I was a little confused that the top level makefile only generates documentation.)

No problem, anything else that was confusing as a first-time port builder? Would like to make this accessible as possible.

[julianrendell]

(I was a little confused that the top level makefile only generates documentation.)

No problem, anything else that was confusing as a first-time port builder? Would like to make this accessible as possible.

Over all, very impressed - better than what I got to see over peoples shoulder 10 years ago from commercial vendors (worked adjacent to base port devs.) it would be helpful to have a few short readme files sprinkled around in the HAL, binding, driver directories for both the shares and port directories. I imagine if you’ve seen a BSP package before/HAL abstractions it might be a different kind of confusing due to some of it being for python bindings.

[tannewt]

Over all, very impressed - better than what I got to see over peoples shoulder 10 years ago from commercial vendors (worked adjacent to base port devs.) it would be helpful to have a few short readme files sprinkled around in the HAL, binding, driver directories for both the shares and port directories. I imagine if you’ve seen a BSP package before/HAL abstractions it might be a different kind of confusing due to some of it being for python bindings.

In case you haven't seen, all of the shared-bindings APIs are documented inline in the C source files: https://github.com/adafruit/circuitpython/blob/main/shared-bindings/digitalio/DigitalInOut.c#L46

[julianrendell]

In case you haven't seen, all of the shared-bindings APIs are documented inline in the C source files: https://github.com/adafruit/circuitpython/blob/main/shared-bindings/digitalio/DigitalInOut.c#L46

Thanks @tannewt - I just found that info while looking at RTD/Sphinx doc generation. I seem to be 'gifted' at looking for info in the wrong place... while there are large, blinking, vibrantly coloured signs pointing to it over there.

[fede2cr]

Followed the instructions and seem to work fine, as well as the debug stuff which I've never done before.
I agree on clarifying the port directory as an instruction.

[tannewt]

Thank you all. Looks like discussion has settled on this PR and it's been tested. So, approving and merging.