Shared I2C bus example

[timoklingenhoefer]

I am fairly new to embedded rust, and I have been struggling to get more than 1 I2C device working on a bus.

The problem is that any sensor owns the I2cDriver so that it can only be used once. The RefCellDevice from embedded_hal_bus is supposed to be the solution for this, but I can`t get it to compile without trait constraint errors.

Can somebody provide an example as to how to get multiple I2C devices to work on a single bus?

Here is what I tried (abbreviated from my original code):

use std::cell::RefCell;
use esp_idf_hal::{delay, i2c, prelude::Peripherals};
use esp_idf_sys::EspError;

use bme280::i2c::BME280;
use mlx9061x::{Mlx9061x, SlaveAddr};

use embedded_hal_bus::i2c as i2c_bus;

fn main() -> Result<(), EspError> {
    esp_idf_sys::link_patches();

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

    let scl1 = peripherals.pins.gpio15;
    let sda1 = peripherals.pins.gpio2;
    let i2c0 = i2c::I2cDriver::new(
        peripherals.i2c0,
        sda1,
        scl1,
        &i2c::config::Config::new().baudrate(100.kHz().into())
    )?;


    let i2c_ref_cell = RefCell::new(i2c0);

    let mut bme280 = BME280::new_primary(i2c_bus::RefCellDevice::new(&i2c_ref_cell));
    bme280.init(&mut delay::Ets).unwrap();

    let addr = SlaveAddr::default();
    let mut mlx90614 = Mlx9061x::new_mlx90614(i2c_bus::RefCellDevice::new(&i2c_ref_cell), addr, 5).unwrap();

    let amb_temp = bme280.measure(&mut delay::Ets).unwrap();
    let obj_temp = mlx90614.object1_temperature().unwrap();
}

This fails to compile with

error[E0277]: the trait bound `embedded_hal_bus::i2c::RefCellDevice<'_, I2cDriver<'_>>: embedded_hal::blocking::i2c::WriteRead` is not satisfied

at Mlx9061x::new_mlx90614(....)

My dependecies are:

esp-idf-hal = "0.43.0"
esp-idf-sys = "0.34.0"
bme280 = "0.5.0"
mlx9061x = "0.2.1"
embedded-hal-bus = "0.1.0"
embedded-hal = "1.0.0"

[Vollbrecht]

The problem is your mlx9061x driver crate you are using. You are currently using the embedded-hal-bus version that is using embedded-hal v1.0.0. The bme280 crate is also using embedded-hal v1.0 but the mix9061 crate still uses embedded-hal 0.2 and thats why you got that conflict. While in esp-idf-hal we supports both e-hal 0.2 and e-hal 1.0, on any instance you need to use either one or the othere in your drivers that share a bus. You cant mix them on one embedded-hal-bus implementation.

[Vollbrecht]

Closing as advice was given. For deeper information the embedded-hal repository also offers some information. We fully support embedded-hal but its concrete usage is not specific to esp-idf-hal