Add orange to epd7in3e

[missionfloyd]

I noticed that palette index 4 is skipped for Spectra 6 panels.

e-Paper/RaspberryPi_JetsonNano/python/lib/waveshare_epd/epd7in3e.py

Line 183 in ecdd8cf

pal_image.putpalette( (0,0,0, 255,255,255, 255,255,0, 255,0,0, 0,0,0, 0,0,255, 0,255,0) + (0,0,0)*249)

So I tried sending 0x04, and it turns out it's actually capable of displaying orange.

(Code that created this image)

buf = []
for i in range(7):
    buf += [(i << 4) + i] * int(width * height / 14)

epd.display(buf)

This fills in the missing slot with orange. I've only done it for python because I'm not as familiar with how the C libraries work.

[psiegl]

That is pretty cool! Thanks for the hint, will try it as well. Which Spectra did you use?
EDIT: tried on a 13.3' Spectra 6, seems to not work on this one.

[missionfloyd]

I have the 7.3 inch
https://www.waveshare.com/product/raspberry-pi/displays/e-paper/7.3inch-e-paper-hat-e.htm

[psiegl]

So, I tried to use orange on a 4.0', 7.3' and 13.3' Spectra 6 EPD.
7.3' -> looks like a charm
4.0' & 13.3' -> overall picture becomes more grayish not nice.

[cfhsu]

Just found this blog and the author has very interesting findings. Hope this will help.
https://myembeddedstuff.com/e-ink-spectra-6-color

[psiegl]

@cfhsu thanks for sharing. However, the author of this blogpost highlights in the table, that Orange is just emulated through dittering. This PR here wants to enable the not official Orange support in the 7.0' Spectra E6. Which is not given in 4.0' and not 13.3' Spectra E6.