Waveshare epaper display 2.13 v4

[jsineau-asulab]

I would like to suggest you a driver dedicated to the Waveshare epaper display 2.13 v4 (full and partial refresh, landscape orientation only)
pico_epaper_213_v4.py

[peterhinch]

Thanks for the contribution.. The first line reads

# pico_epaper_213_v4.py A display driver for the Waveshare Pico ePaper 4.2" display.

which is rather confusing. I suggest you include a code comment with a link to the exact Waveshare display.

I'll review this over the next few days. I don't usually publish drivers for hardware I don't possess for obvious support reasons, but I may do in this case with a disclaimer.

[jsineau-asulab]

Yes, I read these red warnings. And I follow your recommendations in your eclock_async.py example, a full refresh every 30 min.
I use this screen only to learn the e-paper display technology and for private project.

I shared with you my project. Once this project is stable, it will become public.
Currently, with this project, I display an analog clock only. I use partial refresh every minute and full refresh every 30 min.
I suggest you to check the display during the partial refresh, some parts become gray and not black... May be, or probably a mistake from I.

Thank you Peter.

[jsineau-asulab]

My driver is bugged...
I set the width and height like a portrait orientation display but I initiate the Framebuf objet with theses properties inverted.
Therefore, on one side, micropython-nano-gui works with portrait orientation and Framebuf works with landscape orientation.

My job isn't complete... My apologies.

[peterhinch]

Thanks for the warning. My display arrived today, but I'll hold off doing any testing until you have an update.

Have you tested the driver with micro-gui?

Please see my comment below.

[peterhinch]

I did perform the standard hardware check and your bug is evident.

It is essential that this produces pixel perfect results otherwise there will be errors when you try to use the GUIs. In particular the squares at either corner must align perfectly with the limits of the display with no missed lines or white pixels beyond the lines. If a display driver passes this test then nano-gui should work. It does seem that there is more wrong than the obvious orientation issue: the one visible square appears misaligned.

[EDIT]
Please see this Waveshare driver. It runs the aclock.py demo in landscape or portrait mode albeit landscape mode clips the topmost pixels.
You'll need to use this PR to avoid the "incompatible device driver" exception.

In my testing the Waveshare driver partial mode does not work.

[jsineau-asulab]

It my first time, and now I see that I miss him a lot of knowledges about display driver. Thank you for your suggestions and I will fix all bugs (I will try) as soon as possible.
But I think that is mandatory to understand the Framebuffer correctly I follow your suggestions.
I will be back ;)

Thank you Peter.

[peterhinch]

I have now studied the official Waveshare driver in detail and tested it. These are my observations:

1. The driver basically works in portrait and landscape mode.
2. It has no support for partial updates (if you attempt to instantiate it in partial mode it raises an exception).
3. Some minor changes are required for nano-gui compatibility.
4. Its registration with the physical display is imprecise. This is because the pixel dimensions of the display are not integer multiples of 8. Framebuf is based on an array of pixels however 250 pixels with 8 pixels per byte corresponds to 31.25 bytes.
5. The displayPartial method is unused and does not work.

My ePaper display drivers are based on manufacturer's drivers. This is because the parameters used to configure the display are based on knowledge of both the controller and the display: only the manufacturer has access to the latter. Consequently if the module manufacturer does not support partial mode, nor will I.

You are, of course, free to experiment with doing this if you wish. I'd be interested to hear if you have success. If you publish a driver with a working partial mode I'd be prepared to link to it in the docs (with an observation re unofficial code).

I intend to publish a driver based on the Waveshare one. I have fixed issue 3 above and am working on a solution to 4.

[peterhinch]

I have now published a driver. It supports a logical display size of 250x120 pixels, and is based on the Waveshare driver but with a number of corrections to enable it to support the relevant demos and tests.

[jsineau-asulab]

Hi Peter,
I'm a young padawan, You are too fast for me. 😊
I hope to find the time next week to play with your driver and understand all faces a E-Paper display.
Thank you.

[peterhinch]

Docs here. Enjoy!