DFRobot Gravity CH423 I2C 24-Channel IO Expansion Module

A project running low on GPIO pins normally has to choose between a cheap shift register (output-only, no interrupt support) or a full-featured but pricier IO expander. The CH423 sits in a genuinely useful middle ground: 24 total digital ports over one I2C connection, split between 8 general-purpose I/O pins that support interrupts (so the host can react to an input change rather than polling constantly) and 16 dedicated output pins with enough drive current to power LEDs directly.

At 15mA continuous current per output, it can directly power up to 24 LEDs statically or 128 LEDs when multiplexed - genuinely useful headroom compared to expanders that need an external driver stage for anything beyond signal-level loads. The I2C address range (0x20-0x3F) leaves room to run several CH423 modules on the same bus for projects needing even more expanded I/O.

Common uses are large LED matrix or indicator panel projects needing more outputs than a microcontroller has pins, expanding both inputs (with interrupt support) and outputs from a single I2C device, and any pin-constrained project where a basic shift register's output-only limitation is a dealbreaker.