First colours on a Spectra 6 panel

A four-inch six-colour e-paper panel on the bench, eighteen months before the device had a name.

The desk device started with a panel, not a plan: a Good Display GDEP040E01, a four-inch six-colour Spectra 6 e-paper module, driven from an Arduino board by Good Display's sample code. The first frame was a hard-coded image, 400 by 600 pixels at 4 bits each, 240,000 bytes compiled into the firmware.

Two facts from that bench shaped the design later. A full refresh is slow, measured in tens of seconds, and a single frame is a large share of a microcontroller's own memory. Anything dynamic would have to arrive as a finished frame, fetched when it is needed, not drawn on the device.