Module adc 

Analog to Digital Converter (ADC)

Overview

The ADC is integrated on the chip, and is capable of measuring analog signals from specific analog I/O pins. One or more ADC units are available, depending on the device being used.

Configuration

The ADC can be configured to measure analog signals from specific pins. The configuration includes the resolution of the ADC, the attenuation of the input signal, and the pins to be measured.

Some targets also support ADC calibration via different schemes like basic calibration, curve fitting or linear interpolation. The calibration schemes can be used to improve the accuracy of the ADC readings.

Examples

Read an analog signal from a pin

let mut adc1_config = AdcConfig::new();
let mut pin = adc1_config.enable_pin(peripherals.GPIO1, Attenuation::_11dB);
let mut adc1 = Adc::new(peripherals.ADC1, adc1_config)?;

let mut delay = Delay::new();

loop {
    let pin_value = nb::block!(adc1.read_oneshot(&mut pin))?;

    delay.delay_millis(1500);
}

Implementation State

• ADC calibration is not implemented for all targets.
• The ESP32-C3 has an ADC2 in silicon, but it is not exposed due to hardware errata in its digital controller. GPIO5 is therefore not an ADC pin on ESP32-C3.
• The ESP32-S31 has no calibration scheme: calibration eFuses and curve fitting coefficients are not available for this chip.
• The ESP32-S31 SAR ADC has one attenuation setting, so the attenuation given to AdcConfig::enable_pin has no effect.
• The ESP32-S31 SAR is differential and its result is the weighted sum of 17 redundant comparator bits. Readings run from 0 to FULL_SCALE (4393), and an input tied to ground reads about ZERO_DIFF_CODE (2198), so a single-ended measurement only uses the codes above that point.

Structs

Adcunstable

Analog-to-Digital Converter peripheral driver.

AdcCalBasicunstable

Basic ADC calibration scheme.

AdcCalCurveunstable

Curve fitting ADC calibration scheme.

AdcCalLineunstable

Line fitting ADC calibration scheme.

AdcConfig

Configuration for the ADC.

AdcPin

An I/O pin which can be read using the ADC.

Enums

Attenuation

The approximate attenuation of the ADC pin.

Errorunstable

Errors that can occur while using the ADC.

Traits

AdcCalScheme

A trait abstracting over calibration methods.

AdcChannel

A helper trait to get the ADC channel of a compatible GPIO pin.

AdcHasCurveCalunstable

Marker trait for ADCs that support curve fitting.

AdcHasLineCalunstable

Marker trait for ADC units which support line fitting.

Instanceunstable

Enables asynchronous access.