Font Rendering and Partial Drawing

A project log for EPDiy: 9.7"/6" E-Paper controller

I always wanted a large, affordable E-Ink screen to play around with. This board talks to cheap E-Reader replacement screens with an ESP32.

valentinValentin 11/18/2019 at 21:440 Comments

Now, finally I implemented what these displays where originally designed for: displaying text. Unfortunately, the ESP32 does not have enough RAM for a real frame buffer (maybe a version 2 will use a module with PSRAM). So, I have to resort to partial refresh / drawing. 

For the image shown above, I first displayed a full-screen grayscale image as usual. Then, I cleared the middle area and proceeded to draw the text line-by-line. If you screen content does not need to be updated often, this should suffice. Otherwise, you can always stream frames via wifi.

For my tests I used the latin1 character set and the Fira Sans font, however, this is completely customizable.