Very specifically, for RP2040 devices with a 72x40 SPI display.
This is a micropython native module which rapidly updates a monochrome display to achieve a greyscale image. It provides a normal greyscale framebuffer supporting all the usual primitive operations, and uses the RP2040's second core handle re-rendering and updating the display.
I created it for a tiny computer in a brick (https://www.youtube.com/watch?v=0pUV_3qeHog), but it also works on the Thumby.
If you don't want to build it yourself, you just need to copy ugrey.mpy to your device, and import it.
import ugrey
with ugrey.Device() as display:
display.start()
fb = display.framebuffer
while True:
fb.fill(0)
# normal framebuf drawing shenanigans
display.show()
After initialising the device (but before starting it), you can configure some settings:
display.grey_bits is the number of bits of greyscale. 1 is monochrome, 3 is probably as high as it's worth going.
display.dither_bits can be 0 or 1 - whether to add dithering into the mix.
display.temporal_dither - whether to alternate the dithering each frame
You can also initialise it with ugrey.Device(bpp=x), and let it choose sensible defaults for the given bit depth. The default is 4, which gives you 3 bits of grey + 1 bit of dither in a GS4 framebuffer. bpp=8 keeps the same output settings but gives you a GS8 framebuffer.
If you don't supply a framebuffer, it will create its own using a format which fits the requested bit depth.
Depending on your display you might need to fiddle with display.frame_period - SSD1306 displays should work at around 5500 uS. I've had some which can't lock at this frequency, but work at 6400.