A side-by-side comparison of the three serial buses every microcontroller project runs into — I2C, SPI and UART — across four axes: number of signal lines, speed, how many devices you can hang off them, and wiring distance. Includes a decision flow and what to look for on a scope.
A complete guide to the MCP23017 I/O expander with schematics. Add 16 GPIO pins to an ESP32 over I2C, set the address with A0–A2, and drive 8 LEDs and 3 switches with the Adafruit_MCP23X17 library. Step by step, with full sample code.
Part 1 of building a network-connected digital clock with an ESP32. Six large LCD panels driven through three MCP23017 I/O expanders, NTP time sync backed by an RTC, the whole thing laid out as a PCB in KiCad 8.x and ordered from JLCPCB.