ina3221

Embedded driver for the INA3221 triple-channel power monitor in Rust.

The INA3221 is very similar to the classic INA219 power monitor IC.

Compatibility

Any board that supports embedded-hal blocking 1.0 I2c should be compatible with this library.

NOTE: Some HALs require feature flagging to enable 1.0 functionality, for example esp-hal requires the eh1 feature.

Installation

You can add via crates.io:

$ cargo add ina3221

NOTE: Some HALs require feature flagging to enable 1.0 functionality, for example esp-hal requires the eh1 feature.

Documentation

You can find the documentation here.

Example

This example assumes a 0.1 Ohm shunt resistor for current and power calculations.

const INA3221_I2C_ADDR: u8 = 0x40;
const SHUNT_RESISTANCE: f32 = 0.1f32;   // 0.1 Ohm

use ina3221::INA3221;

fn main() {
    let i2c = I2C::new(/* initialize your I2C here */);
    let ina = INA3221::new(i2c, INA3221_I2C_ADDR);

    let mut delay = Delay::new(/* initialize your delay/clocks */);

    loop {
        for channel in 0..3 {
            let shunt_voltage = ina.get_shunt_voltage(channel).unwrap();
            let bus_voltage = ina.get_bus_voltage(channel).unwrap();
            
            // Voltage can be added using the '+' operator on the unit type
            let load_voltage = bus_voltage + shunt_voltage;

            // Skip channel if no voltage present
            if shunt_voltage.is_zero() {
                continue;
            }
            
            // Use Ohm's Law to calculate current and power with known resistance
            let current_milliamps = shunt_voltage.milli_volts() / SHUNT_RESISTANCE;
            let power_milliwatts = current_milliamps * load_voltage.volts();
            
            println!(
                "Channel {}: load = {:.3} V, current = {:.3} mA, power = {:.3} mW",
                channel_index + 1,
                load_voltage.volts(),
                current_milliamps,
                power_milliwatts,
            );
        }
        
        delay.delay_ms(1000u32);
    }
}

Output

This is sample output powering an Arduino Uno R3 over USB, running the blinky script.

Channel 1: load = 5.212 V, current = 36.800 mA, power = 191.790 mW
Channel 1: load = 5.211 V, current = 33.600 mA, power = 175.102 mW
Channel 1: load = 5.212 V, current = 36.800 mA, power = 191.790 mW
Channel 1: load = 5.219 V, current = 34.000 mA, power = 177.460 mW
Channel 1: load = 5.212 V, current = 36.800 mA, power = 191.790 mW
Channel 1: load = 5.211 V, current = 34.000 mA, power = 177.188 mW
Channel 1: load = 5.211 V, current = 34.000 mA, power = 177.188 mW
Channel 1: load = 5.212 V, current = 36.400 mA, power = 189.704 mW
Channel 1: load = 5.211 V, current = 34.000 mA, power = 177.188 mW
Channel 1: load = 5.212 V, current = 36.800 mA, power = 191.790 mW
Channel 1: load = 5.211 V, current = 34.000 mA, power = 177.188 mW