Full-color (okay, 16- or 18-bit color) LCD and LED displays have been available as breadboardable, microcontroller-friendly modules for several years now. Recently, though, round displays have been appearing in hobbyist-friendly form. These can be thought of as rectangular displays that simply don’t implement pixels that aren’t in the circle radius.
GC9A01 display modules use an SPI bus interface, which is slightly more involved to set up than the ubiquitous I2C (or “Wire”) interface. There’s a good reason for this — at 240×240 resolution (really 120px radius), that’s some 45,000 pixels per frame, or north of 800,000 pixels. If you want to do any kind of video or animation, you need several frames per second. SPI is generally used for higher data rate applications, since it can run at 8Mb or more.
I followed the instructions in this video to get the display set up using a standard ESP32 dev board module. The Arduino GFX Graphics Library referenced in the video can drive the GC9A01 via the usual set of APIs for drawing pixels, lines, circles, etc.
Do note that these are 3.3V parts — it’s best to drive them with something modern and fast like an ESP32, which will probably be a 3v3 part itself. An Arduino Uno or PIC16F84A or 8051 could work with these, though — just very slowly. Maybe I’ll get the DrACo/Z80 to run one (via a voltage divider, at least).
They’d make great aircraft instrument replica displays, if only they were a little larger…
