Colour e-ink decides the chip

The desk device shows a word, a phrase and a picture on e-ink. A comparison of two 800 by 480 panels, 2-bit grayscale and six-colour Spectra 6, decided most of the hardware before any board was drawn.

Colour doubles the framebuffer, and with the download and text buffers the working memory reaches 600 to 800 KB, more than the ESP32's internal RAM. PSRAM stopped being optional and the ESP32-S3 became the only candidate. The screen pays too: a full refresh takes 8 to 15 seconds instead of about one. Colour won, and the design changed: content arrives as whole frames, not small text updates.