MeadowApp.cs

using Meadow;
using Meadow.Devices;
using Meadow.Foundation.Displays;
using Meadow.Foundation.Graphics;
using Meadow.Foundation.Leds;
using Meadow.Foundation.Sensors.Hid;
using Meadow.Hardware;
using Meadow.Peripherals.Displays;
using System.Threading.Tasks;

namespace TouchKeypad;

// public class MeadowApp : App<F7FeatherV1> <- If you have a Meadow F7v1.*
public class MeadowApp : App<F7FeatherV2>
{
    Mpr121 sensor;
    MicroGraphics graphics;

    public override Task Initialize()
    {
        var onboardLed = new RgbPwmLed(
            redPwmPin: Device.Pins.OnboardLedRed,
            greenPwmPin: Device.Pins.OnboardLedGreen,
            bluePwmPin: Device.Pins.OnboardLedBlue);
        onboardLed.SetColor(Color.Red);

        var display = new St7789(
            spiBus: Device.CreateSpiBus(),
            chipSelectPin: Device.Pins.D02,
            dcPin: Device.Pins.D01,
            resetPin: Device.Pins.D00,
            width: 240, height: 240);

        graphics = new MicroGraphics(display)
        {
            Stroke = 2,
            Rotation = RotationType._180Degrees,
            CurrentFont = new Font12x16(),
        };

        sensor = new Mpr121(Device.CreateI2cBus(I2cBusSpeed.Standard), 90, 100);
        sensor.ChannelStatusesChanged += SensorChannelStatusesChanged;

        onboardLed.SetColor(Color.Green);

        return base.Initialize();
    }

    void DrawGrid()
    {
        graphics.Clear();
        for (int columns = 0; columns < 3; columns++)
        {
            for (int rows = 3; rows >= 0; rows--)
            {
                graphics.DrawRectangle(columns * 57 + 38, rows * 57 + 10, 51, 51, Color.Cyan);
            }
        }
        graphics.Show();
    }

    void SensorChannelStatusesChanged(object sender, ChannelStatusChangedEventArgs e)
    {
        graphics.Clear();
        graphics.Stroke = 1;

        for (int i = 0; i < e.ChannelStatus.Count; i++)
        {
            int numpadIndex = 0;
            for (int columns = 0; columns < 3; columns++)
            {
                for (int rows = 3; rows >= 0; rows--)
                {
                    if (numpadIndex == i)
                    {
                        if (e.ChannelStatus[(Mpr121.Channels)i])
                            graphics.DrawRectangle(columns * 57 + 38, rows * 57 + 10, 51, 51, Color.Cyan, true);
                        else
                            graphics.DrawRectangle(columns * 57 + 38, rows * 57 + 10, 51, 51, Color.Cyan);
                    }
                    numpadIndex++;
                }
            }
        }

        graphics.Show();
    }

    public override Task Run()
    {
        DrawGrid();

        return base.Run();
    }
}