eldruin/pcf857x-rs

Platform agnostic driver for the PCF8574, PCF8574A and PCF8575 I/O expanders written in Rust using embedded-hal

Rust PCF857x I/O Expanders Driver

This is a platform agnostic Rust driver for the PCF8574, PCF8574A and PCF8575 I2C I/O expanders, based on the embedded-hal traits.

This driver allows you to:

• Set all the outputs to 0 or 1 at once. See set().
• Read selected inputs. See get().
• Set all the outputs repeatedly looping through an array. See write_array().
• Read selected inputs repeatedly filling up an array. See read_array().
• Split the device into individual input/output pins. See split().

The devices

The devices consist of 8 or 16 quasi-bidirectional ports, I²C-bus interface, three hardware address inputs and interrupt output. The quasi-bidirectional port can be independently assigned as an input to monitor interrupt status or keypads, or as an output to activate indicator devices such as LEDs.

The active LOW open-drain interrupt output (INT) can be connected to the interrupt logic of the microcontroller and is activated when any input state differs from its corresponding input port register state.

Datasheets:

• PCF8574 / PCF8574A
• PCF8575

Usage

Please find additional examples using hardware in this repository: driver-examples

use linux_embedded_hal::I2cdev;
use pcf857x::{Pcf8574, PinFlag, SlaveAddr};

fn main() {
    let dev = I2cdev::new("/dev/i2c-1").unwrap();
    let address = SlaveAddr::default();
    let mut expander = Pcf8574::new(dev, address);
    let output_pin_status = 0b1010_1010;
    expander.set(output_pin_status).unwrap();

    let pins_to_be_read = PinFlag::P0 | PinFlag::P7;
    let status = expander.get(pins_to_be_read).unwrap();

    println!("Input pin status: {}", status);
}

Support

For questions, issues, feature requests, and other changes, please file an issue in the github project.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contributing

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

pcf857x-rs's Issues

Offer embedded-hal Pin interface

A split() method should be added that returns the GPIO pins broken into individual generic embedded-hal Pins.
Examples of this are:

• https://github.com/japaric/stm32f103xx-hal/blob/687dc4b2eda17ec20f5a6fd8ffe411297eaef9d1/src/gpio.rs#L81
• https://github.com/therealprof/nrf51-hal/blob/0ea22ead03143c2ae16cf059f08390f71fa71577/src/serial.rs#L69

Use u32 as input for PCF8575 instead of u16

PCF8575 has 18 output pins, so u16 doesn't have enough bits for that. A workaround is to set through an array, but it's just a workaround.

Pins don't implement Peripheral

Looks like there is a lack of impl DerefMut for pins.
Example:

fn main() -> eyre::Result<()> {
    // It is necessary to call this function once. Otherwise some patches to the runtime
    // implemented by esp-idf-sys might not link properly. See https://github.com/esp-rs/esp-idf-template/issues/71
    esp_idf_svc::sys::link_patches();

    let peripherals = Peripherals::take().unwrap();

    let i2c = peripherals.i2c0;
    let sda = peripherals.pins.gpio5;
    let scl = peripherals.pins.gpio6;

    let config = I2cConfig::new().baudrate(100.kHz().into());
    let i2c = I2cDriver::new(i2c, sda, scl, &config)?;
    let mut expander: Pcf8574<I2cDriver> = pcf857x::Pcf8574::new(i2c, SlaveAddr::Alternative(true, true, true));
    let parts = expander.split();

    fn test<'d>(p: impl Peripheral<P = impl OutputPin> + 'd) {
        todo!()
    }
    
    test(parts.p0); // doesn't work
}

Error:

error[E0277]: the trait bound `P0<'_, Pcf8574<I2cDriver<'_>>, I2cError>: DerefMut` is not satisfied
  --> examples/uln2003_via_pcf8574.rs:42:10
   |
42 |     test(parts.p0);
   |     ---- ^^^^^^^^ the trait `DerefMut` is not implemented for `P0<'_, Pcf8574<I2cDriver<'_>>, I2cError>`
   |     |
   |     required by a bound introduced by this call
   |
   = help: the following other types implement trait `Peripheral`:
             AnyIOPin
             AnyInputPin
             AnyOutputPin
             Modem
             ADC1
             ADC2
             CAN
             Gpio0
           and 46 others
   = note: required for `P0<'_, Pcf8574<I2cDriver<'_>>, I2cError>` to implement `Peripheral`
note: required by a bound in `test`
  --> examples/uln2003_via_pcf8574.rs:38:25
   |
38 |     fn test<'d>(p: impl Peripheral<P = impl OutputPin> + 'd) {
   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `test`

Implement fallible OutputPin/InputPin traits

See rust-embedded/embedded-hal#95 and rust-embedded/embedded-hal#108