Crate port_expander

This is a crate providing a common abstraction for I²C port-expanders. This abstraction is not necessarily the most performant, but it allows using the pins just like direct GPIOs. Because the pin types also implement the embedded-hal digital IO traits, they can also be passed to further drivers downstream (e.g. as a reset or chip-select pin).

Example

// Initialize I2C peripheral from HAL
let i2c = todo!();

// A0: HIGH, A1: LOW, A2: LOW
let mut pca9555 = port_expander::Pca9555::new(i2c, true, false, false);
let pca_pins = pca9555.split();

let io0_0 = pca_pins.io0_0.into_output().unwrap();
let io1_5 = pca_pins.io0_1; // default is input

io0_0.set_high().unwrap();
assert!(io1_5.is_high().unwrap());

Accessing multiple pins at the same time

Sometimes timing constraints mandate that multiple pin accesses (reading or writing) happen at the same time. The write_multiple() and read_multiple() methods are designed for doing this.

Supported Devices

The following list is what port-expander currently supports. If you needs support for an additional device, it should be easy to add. It’s best to take a similar existing implementation as inspiration. Contributions welcome!

• MAX7321
• PCA9536
• PCA9538
• PCA9555
• PCF8574A
• PCF8574
• PCF8575
• TCA6408A

Non-local sharing

port-expander uses a custom trait for abstracting different kinds of mutexes: PortMutex. This means you can also make the pins shareable across task/thread boundaries, given that you provide an appropriate mutex type:

// Initialize I2C peripheral from HAL
let i2c = todo!();

// A0: HIGH, A1: LOW, A2: LOW
let mut pca9555: port_expander::Pca9555<std::sync::Mutex<_>> =
    port_expander::Pca9555::with_mutex(i2c, true, false, false);
let pca_pins = pca9555.split();

Re-exports

• pub use dev::max7321::Max7321;
• pub use dev::pca9536::Pca9536;
• pub use dev::pca9538::Pca9538;
• pub use dev::pca9555::Pca9555;
• pub use dev::pcal6408a::Pcal6408a;
• pub use dev::pcal6416a::Pcal6416a;
• pub use dev::pcf8574::Pcf8574;
• pub use dev::pcf8574::Pcf8574a;
• pub use dev::pcf8575::Pcf8575;
• pub use dev::tca6408a::Tca6408a;

Modules

• dev
  The device module contains the internals for each of the supported port expanders.
• mode
  Pin Modes

Structs

• Pin
  Representation of a port-expander pin.

Traits

• I2cBus
  Blanket trait for types implementing `i2c::I2c
• PortMutex
  Common interface for mutex implementations.

Functions

• read_multiple
  Read multiple pins at the same time.
• write_multiple
  Set multiple pins at the same time.