IO Expansion

Christoph TackChristoph Tack wrote 10/06/2019 at 08:48 • 3 min read • Like

There's more IO needed than the BluePill can handle.  We need an IO Expander.

The IO expander also controls the 15 LEDs in this setup using charlieplexing.  A charlieplexing library for the MCP23017 has been developed, loosely based on the Chaplex library.

An alternative approach would be to use a 16 channel SPI LED driver instead: TLC5925 | STP16CPC26 | CAT4016 | MAX6969: 16 outputs, integrated current source, Digikey €1/pce.  This would allow me to get rid of the charlieplexing, which would ease timing a bit.