Add support for IT8951 based displays #31
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I've tested this with a 6 inch display that uses the IT8951 controller board with both VNC and terminal and it seems to work well. I haven't tested with a 9 inch display but there isn't anything display specific in the driver (that I'm aware of) so it should just work. This implantation is based off the WaveShare sample code in https://github.com/waveshare/IT8951. There are some idiosyncrasies in that code that I don't understand and aren't documented but appear necessary. For example, manually controlling the CS pin instead of letting the SPI driver code handle it... Issue joukos#25
Previously the driver was using 8 bits-per-pixel for SPI transfers. This is wasteful sine the actual display only supports 16 different gray levels. This updates the code to use a packed format that uses 4 bits-per-pixel. There is the potential for further optimization when rendering text (or other pure black and white images) to use 2 bits-per-pixel. However, when I tried this the fast display mode did not properly clear pixels between blits. Issue joukos#25
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Thank you so much for this awesome contribution! Makes me want to order one of the new 10.3" displays to try it out ;) I also appreciate the clarifying comments in the code. I merged this now and will update the project README to mention it. |
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I've tested this with a 6 inch display that uses the IT8951 controller board with both VNC and terminal and it seems to work well. I haven't tested with a 9 inch display but there isn't anything display specific in the driver (that I'm aware of) so it should just work.
Despite also being a SPI device there doesn't appear to actually be that much in common between this driver and the other display drivers so I ended up sub-classing from DisplayDriver instead of WaveshareEPD which has some SPI and GPIO bootstrapping.