Why so many screens?
Why not! But also because the BSidesCapeTown 2019 badge uses an ST7789 TFT screen, and I have a lot of them left over from the prototyping/destroying/burning/crying phase. Adafruit has a library for them, so my thinking was “how hard could it be to adapt this to drive multiple screens?”. Famous last words of course.
They’re driven using SPI (Serial Peripheral Interface). How does SPI work? It’s usually a clock line (CLK), one or more data lines (Dx), and a Chip Select (CS) line. The CLK and Dx lines are connected to all devices on the ‘bus’, and one CS line is used per device. When the CS line for a particular device is active, it will accept commands, otherwise it ignores them. Easy! Unfortunately the CS line on these screens is hard-wired to active, probably to save space – the screen needs two extra lines: reset (RST) and data/command mode (DC).