Crate mcp3425 [−] [src]

A platform agnostic Rust driver for the MCP3425, based on the embedded-hal traits.

The Device

The Microchip MCP3425 is a low-current 16-bit analog-to-digital converter.

The device has an I²C interface and an on-board ±2048mV reference.

Details and datasheet

Usage

Instantiating

Import this crate and an embedded_hal implementation:

extern crate linux_embedded_hal as hal;
extern crate mcp3425;

Then instantiate the device in either ContinuousMode or OneShotMode:

use hal::{Delay, I2cdev};
use mcp3425::{MCP3425, Config, Resolution, Gain, Error, OneShotMode};

let dev = I2cdev::new("/dev/i2c-1").unwrap();
let address = 0x68;
let mut adc = MCP3425::new(dev, address, Delay, OneShotMode);

(You can also use the shortcut functions oneshot or continuous to create instances of the MCP3425 type without having to specify the type as parameter.)

Configuration

You can choose the conversion resolution / sample rate and the PGA gain with a Config object.

Use the methods starting with with_ to create a (side-effect free) new instance of the configuration where the specified setting has been replaced.

let config = Config::new(Resolution::Bits12Sps240, Gain::Gain1);
let high_res = config.with_resolution(Resolution::Bits16Sps15);
let high_gain = high_res.with_gain(Gain::Gain8);

Measurements

One-Shot

You can trigger a one-shot measurement:

let mut adc = MCP3425::oneshot(dev, address, Delay);
let config = Config::new(Resolution::Bits12Sps240, Gain::Gain1);
match adc.measure(&config) {
    Ok(voltage) => println!("ADC measured {} mV", voltage.as_millivolts()),
    Err(Error::I2c(e)) => println!("An I2C error happened: {}", e),
    Err(Error::VoltageTooHigh) => println!("Voltage is too high to measure"),
    Err(Error::VoltageTooLow) => println!("Voltage is too low to measure"),
    Err(Error::NotReady) => println!("Measurement not yet ready. This is a driver bug."),
    Err(Error::NotInitialized) => unreachable!(),
}

As you can see, the saturation values are automatically converted to proper errors.

Continuous

You can also configure the ADC in continuous mode:

let mut adc = MCP3425::continuous(dev, address, Delay);
let config = Config::new(Resolution::Bits12Sps240, Gain::Gain1);
adc.set_config(&config).unwrap();
match adc.read_measurement() {
    Ok(voltage) => println!("ADC measured {} mV", voltage.as_millivolts()),
    Err(Error::I2c(e)) => println!("An I2C error happened: {}", e),
    Err(Error::VoltageTooHigh) => println!("Voltage is too high to measure"),
    Err(Error::VoltageTooLow) => println!("Voltage is too low to measure"),
    Err(Error::NotReady) => println!("Measurement not yet ready. Polling too fast?"),
    Err(Error::NotInitialized) => println!("You forgot to call .set_config"),
}

Feature Flags

The following feature flags exists:

measurements: Use the measurements crate to represent voltages instead of the custom Voltage wrapper

Structs

Config	Device configuration: Resolution and gain
ContinuousMode	Use the MCP3425 in Continuous Conversion mode.
MCP3425	Driver for the MCP3425 ADC
OneShotMode	Use the MCP3425 in One-Shot mode.
Voltage	A voltage measurement.

Enums

Error	All possible errors in this crate
Gain	Programmable gain amplifier (PGA)
Resolution	Conversion bit resolution and sample rate

Traits

ConversionMode

The two conversion mode structs implement this trait.