Originally Posted by axsdenied
I was reading about EPD controllers and they seem to be able to easily do 50HZ refresh rates on e-paper screens:
Also, as shown by this demo, the slow refresh is possibly just a software thing and not the e-paper technology.
That 50 Hz is partial non-overlapping region update rate. You can have multiple simultaneous updates in progress, but if they overlap, the get queued up serially. Each update can take up to 300 msec according to the docs. I "overclock" that to 130 msec but not waiting until "ready" before starting another update. Going faster than that causes intolerable artifacts, unless you do region management yourself to prevent overlapping a new region update with a region already in progress.
The K4/K5 use an EPD controller built into the freescale i.Mx508 Soc, which can process 20 simultaneous update reqions, as I recall. The K3 uses an external EPD controller chip that is slower and cannot handle as many simultaneous eink updates.
The overlapping region management in the eink driver code is a bit complex. Interestingly, the K4 booted from main emulates K3 eink in a HAL layer, but when booted from diags it uses K5-style eink management. Of course, that COULD change with a firmware update...