Add support for the epd1in54b display

[jkristell]

This RFC pull request adds support for the 2 color (red and black) display epd1in54b .

To support the two different planes of colored ink I have added a new trait called WaveshareTwoColorDisplay with on method - update_both_planes() for updating both planes at once. The old update_frame() just clears the color-layer when updating the black layer

[codecov-io]

Codecov Report

Merging #35 into master will decrease coverage by 5.52%.
The diff coverage is 2.79%.

@@            Coverage Diff             @@
##           master      #35      +/-   ##
==========================================
- Coverage   41.26%   35.74%   -5.53%     
==========================================
  Files          15       18       +3     
  Lines         853      996     +143     
==========================================
+ Hits          352      356       +4     
- Misses        501      640     +139

Impacted Files	Coverage Δ
src/traits.rs	0% <ø> (ø)	⬆️
src/epd1in54b/graphics.rs	0% <0%> (ø)
src/epd1in54b/command.rs	0% <0%> (ø)
src/epd1in54b/mod.rs	3.1% <3.1%> (ø)

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[caemor]

Looks great on a fast skim. I will make a full review next week, but could you in the meantime please add the new device to the Readme and add a short description/doc comments to the new trait?

[caemor]

See the comment

[jkristell]

Added some documentation.

Perhaps the trait should be named WaveshareThreeColorDisplay instead as that's the terminology that Waveshare use.

[caemor]

Then we should use the same terminology so it's easier for people to switch :-)
And can you please run cargo format, then it would be ready to be merged.
Greetings Chris

[jkristell]

I'm not really happy about the update_both_planes() name. What do you think about renaming it to update_color_frame()?

Naming is hard :)

 fn update_color_frame(
        &mut self,
        spi: &mut SPI,
        black: &[u8],
        color1: &[u8],
    ) -> Result<(), SPI::Error>;

[jkristell]

Trait and method names updated, and code was formatted with cargo fmt.

[caemor]

How is the src/epd1in54b/graphics.rs working for you?
Would someone use two "display1in54b"s - one for red/color and one for black with the embedded graphics library?
I really like your naming changes! :-)

[jkristell]

Graphics works. Yeah exactly like that. Two "displays". I have test code for this that I will clean up and publish as an example in my nucleo-f401re crate.

[jkristell]

https://github.com/jkristell/nucleo-f401re/blob/add-eink-example/examples/eink.rs

[caemor]

Thanks for your work :-)