Table of Contents

MPR121 - Proximity Capacitive Touch Sensor Controller

The 12-channels I2C proximity capacitive touch sensor controller.

Documentation

Usage

Important: make sure you properly setup the I2C pins especially for ESP32 before creating the I2cDevice, make sure you install the nanoFramework.Hardware.ESP32 nuget:

//////////////////////////////////////////////////////////////////////
// when connecting to an ESP32 device, need to configure the I2C GPIOs
// used for the bus
Configuration.SetPinFunction(21, DeviceFunction.I2C1_DATA);
Configuration.SetPinFunction(22, DeviceFunction.I2C1_CLOCK);

For other devices like STM32, please make sure you're using the preset pins for the I2C bus you want to use.

Default configuration with manually updating of channel statuses

var i2cDevice = I2cDevice.Create(new I2cConnectionSettings(busId: 1, deviceAddress: Mpr121.DefaultI2cAddress));
var mpr121 = new Mpr121(device: i2cDevice);

var statuses = mpr121.ReadChannelStatuses();
var status = statuses[Channels.Channel01]
    ? "pressed"
    : "released";

Debug.WriteLine($"The 1st channel is {status}");

Channel statuses auto refresh

var i2cDevice = I2cDevice.Create(new I2cConnectionSettings(busId: 1, deviceAddress: Mpr121.DefaultI2cAddress));

// Initialize controller with default configuration and auto-refresh the channel statuses every 100 ms.
var mpr121 = new Mpr121(device: i2cDevice, periodRefresh: 100);

// Subscribe to channel statuses updates.
mpr121.ChannelStatusesChanged += (object sender, ChannelStatusesChangedEventArgs e) =>
    {
        var channelStatuses = e.ChannelStatuses;
        // do something.
    };

Custom MPR121 registers configuration

var i2cDevice = I2cDevice.Create(new I2cConnectionSettings(busId: 1, deviceAddress: Mpr121.DefaultI2cAddress));
var config = new Mpr121Configuration
{
    MaxHalfDeltaRising = 0x01,
    NoiseHalfDeltaRising = 0x01,
    NoiseCountLimitRising = 0x00,
    FilterDelayCountLimitRising = 0x00,
    MaxHalfDeltaFalling = 0x01,
    NoiseHalfDeltaFalling = 0x01,
    NoiseCountLimitFalling = 0xFF,
    FilterDelayCountLimitFalling = 0x01,
    ElectrodeTouchThreshold = 0x0F,
    ElectrodeReleaseThreshold = 0x0A,
    ChargeDischargeTimeConfiguration = 0x04,
    ElectrodeConfiguration = 0x0C
};

var mpr121 = new Mpr121(device: i2cDevice, configuration: config);

This sample demonstrates how to read channel statuses using auto-refresh configuration.

Handling the channel statuses changes

mpr121.ChannelStatusesChanged += (object sender, ChannelStatusesChangedEventArgs e) =>
    {
        var channelStatuses = e.ChannelStatuses;
        // do something.
    };

Binding Notes

The binding provides different options of device configuration. The device can be configured to update the channel statuses periodically. Also it supports custom configuration of controller registers.

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