LcdRgb.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Device.I2c;
using System.Drawing;

namespace Iot.Device.CharacterLcd
{
    /// <summary>
    /// Supports I2c LCDs with I2c RGB backlight, such as the Grove - LCD RGB Backlight (i.e. 16x2 LCD character display with RGB backlight).
    /// </summary>
    /// <remarks>
    /// This implementation was drawn from numerous libraries such as Grove_LCD_RGB_Backlight.
    /// </remarks>
    public class LcdRgb : Hd44780
    {
        private readonly I2cDevice _rgbDevice;

        private Color _currentColor;
        private bool _backlightOn = true;

        /// <summary>
        /// Initializes a new HD44780 LCD controller.
        /// </summary>
        /// <param name="size">Size of the device in characters. Usually 16x2 or 20x4.</param>
        /// <param name="lcdDevice">The I2C device to control LCD display.</param>
        /// <param name="rgbDevice">The I2C device to control RGB backlight.</param>
        public LcdRgb(Size size, I2cDevice lcdDevice, I2cDevice rgbDevice)
            : base(size, LcdInterface.CreateI2c(lcdDevice, true))
        {
            _rgbDevice = rgbDevice;

            InitRgb();
        }

        /// <summary>
        /// Initializes a new HD44780 LCD with an RGB Backlight.
        /// </summary>
        /// <param name="size">Size of the device in characters. Usually 16x2 or 20x4.</param>
        /// <param name="lcdInterface">Interface to the display.</param>
        /// <param name="rgbDevice">The I2C device to control RGB backlight.</param>
        public LcdRgb(Size size, LcdInterface lcdInterface, I2cDevice rgbDevice)
            : base(size, lcdInterface)
        {
            _rgbDevice = rgbDevice;

            InitRgb();
        }

        /// <summary>
        /// Enable/disable the backlight.
        /// </summary>
        public override bool BacklightOn
        {
            get => _backlightOn;
            set
            {
                ForceSetBacklightColor(value ? _currentColor : Color.Black);
                _backlightOn = value;
            }
        }

        /// <summary>
        /// Sets register for RGB backlight.
        /// </summary>
        /// <param name="addr">The register address.</param>
        /// <param name="value">The register value.</param>
        private void SetRgbRegister(RgbRegisters addr, byte value)
        {
            Span<byte> dataToSend = stackalloc byte[]
            {
                (byte)addr, value
            };
            _rgbDevice.Write(dataToSend);
        }

        /// <summary>
        /// Sets the backlight color without any checks.
        /// </summary>
        /// <param name="color">The color to set.</param>
        private void ForceSetBacklightColor(Color color)
        {
            SetRgbRegister(RgbRegisters.REG_RED, color.R);
            SetRgbRegister(RgbRegisters.REG_GREEN, color.G);
            SetRgbRegister(RgbRegisters.REG_BLUE, color.B);
        }

        /// <summary>
        /// Initializes RGB device.
        /// </summary>
        private void InitRgb()
        {
            // backlight init
            SetRgbRegister(RgbRegisters.REG_MODE1, 0);

            // set LEDs controllable by both PWM and GRPPWM registers
            SetRgbRegister(RgbRegisters.REG_LEDOUT, 0xFF);

            // set MODE2 values
            // 0010 0000 -> 0x20  (DMBLNK to 1, ie blinky mode)
            SetRgbRegister(RgbRegisters.REG_MODE2, 0x20);

            SetBacklightColor(Color.White);
        }

        /// <summary>
        /// Sets the backlight color.
        /// The action will be ignored in case of the backlight is disabled.
        /// </summary>
        /// <param name="color">The color to set.</param>
        public void SetBacklightColor(Color color)
        {
            if (!BacklightOn)
            {
                return;
            }

            ForceSetBacklightColor(color);
            _currentColor = color;
        }

        /// <inheritdoc/>
        public override void Dispose()
        {
            _rgbDevice?.Dispose();
            base.Dispose();
        }
    }
}