Add support for Radxa's Rock Pi 4(C+) Single Board Computers

[wgroeneveld]

Hi,

I've been fiddling with a Raspberry Pi clone for a while and managed to get CircuitPython running on it. I've contributed the correct pinout here this week: adafruit/Adafruit_Blinka#651
But since I wanted to do something in Go with I2C, I stumbled upon Gobot, which doesn't have the correct mapping either. Here's my attempt to add compatibility in Gobot.

Please note that, although I've read the CONTRIBUTING guide, I am unable to run unit tests thanks to a nasty dependency: https://github.com/warthog618/gpiod which literally states: "For other platforms, where you intend to cross-compile for Linux, don't attempt to compile the package when it is installed". On my Mac, I get a lot of errors like "../../../../go/pkg/mod/github.com/warthog618/[email protected]/gpiod.go:326:35: undefined: uapi.LineInfo". On the RockPi itself, the Go version isn't recent enough.
But since the rockpi_adaptor.go is based on the Pi's, and it has reduced functionality, and the most important aspect is the mapping, I figured this is as good as it gets.

Note that Radxa's boards aren't great when it comes to support/compatibility with existing software. The character device gpiod driver doesn't seem to work, and PWM only works through the mraa lib, which could be implemented using cgo, but I didn't yet. I think that's for another contributor!

Thanks for any feedback! Cheers

[gen2thomas]

Hi @wgroeneveld , thanks for sharing your nice work. I will have a deeper look in the next days. What I can say immediately:

• please can you add some of your description of the PR to the README.md, e.g. in a section I2C, PWM, GPIO etc.
• if the gpiod chracter device is known not to work, just remove the "system.WithDigitalPinGpiodAccess()" in the constructor (line 52)

[wgroeneveld]

Great, thanks, I did that, and I managed to add tests by locally removing the problematic dependency!

[gen2thomas]

Hi @wgroeneveld I have finished the PR review for now. For your remark

On my Mac, I get a lot of errors like "../../../../go/pkg/mod/github.com/warthog618/[email protected]/gpiod.go:326:35: undefined: uapi.LineInfo". On the RockPi itself, the Go version isn't recent enough.

We use v0.8.0 in gobot and I had not tested the v0.8.1 yet on my Linux developer machine. If your problem persists, please file an issue at gpiod, because it is most likely not caused by gobot.

[wgroeneveld]

Thank you for your review @gen2thomas , I've changed the files as requested.
I know the gpiod issue isn't caused by gobot, see my previous comments.

[wgroeneveld]

Okay I solved the two open review issues, I think everything looks good now!

[gen2thomas]

Yes, thanks for your rework. I will going to merge now.