epaper2in7.py constructor has a bug

[peterhinch]

This line throws NameError: name 'LUT_BW' isn't defined. Should it read:

LUT_BW = LUT_WW

?

[peterhinch]

Looking at the Waveshare code I think the above fix is correct.

I have failed to get this working: typically the code hangs forever waiting on busy. I now suspect a hardware problem with the reset line and have ordered a replacement panel. While diagnosing this I performed a detailed comparison between your code and that of Waveshare. In the process I spotted some discrepancies between your code and that of Waveshare and would appreciate your comments.

Firstly you don't set this register.

Secondly your LUT values differ, e.g. here.

Any information would be welcome.

[phuzybuny]

@peterhinch Did you manage to get this library to work?

I'm seeing the same discrepancy in the LUT values here as well.

[peterhinch]

My interest in this was to develop my own library for nano-gui so I really just studied the code. I was certain I'd found a bug so I reported it. I didn't make any attempt to make this driver work as my intention was to write a driver subclassed from framebuf.

I should mention that my experience with Waveshare devices has not been good. I ended up with two units with different hardware faults. Perhaps I was unlucky. By contrast I've written drivers for many Adafruit displays: all have worked perfectly.

[phuzybuny]

@peterhinch Thank you for sharing! I see your library supports the 2.7inch e-Paper HAT. Will take a look at nano-gui instead.

Saw your notes about possible quality issues with Waveshare e-Paper displays. I haven't encountered issues with my unit but thank you for bringing it up.