tca6424

no_std Rust driver for the TCA6424A 24-bit I2C GPIO expander.

Supports both synchronous and asynchronous I2C via feature flags, built on embedded-hal v1.

Features

Feature	Description
(default)	Synchronous API using embedded-hal::i2c::I2c
async	Asynchronous API using embedded-hal-async::i2c::I2c
defmt	defmt::Format derives and structured logging
log	log crate logging

Usage

# Synchronous (default)
[dependencies]
tca6424 = "0.1"

# Async (e.g. Embassy on STM32)
[dependencies]
tca6424 = { version = "0.1", default-features = false, features = ["async", "defmt"] }

use tca6424::{Tca6424a, Port};

let mut expander = Tca6424a::new(i2c, 0x22);

// Initialize: config = port directions (0=output, 1=input), output = initial values
expander.init(
    [0x00, 0xF0, 0xFF], // P0: all outputs, P1: lower outputs/upper inputs, P2: all inputs
    [0x00, 0x00, 0x00], // all outputs start low
).await?; // drop .await for sync

// Set specific bits (value, mask)
expander.set_output(Port::P0, 0x05, 0x0F).await?;

// Read all input ports
let inputs = expander.read_inputs().await?;

Register map

Base	Auto-increment	Register
0x00	0x80	Input Port 0-2
0x04	0x84	Output Port 0-2
0x08	0x88	Polarity Inversion Port 0-2
0x0C	0x8C	Configuration Port 0-2

Shadow registers track output, config, and polarity state to skip redundant I2C writes.

License

MIT