NeopixelChain.cs

using nanoFramework.Hardware.Esp32.Rmt;


namespace NFEchoWebSocketServer
{
    public class NeopixelChain
    {
        // 80MHz / 4 => min pulse 0.00us
        protected const byte ClockDivider = 4;
        // one pulse duration in us
        protected const float MinPulse = 1000000.0f / (80000000 / ClockDivider);

        // default datasheet values
        protected readonly RmtCommand OnePulse =
            new RmtCommand((ushort)(0.7 / MinPulse), true, (ushort)(0.6 / MinPulse), false);

        protected readonly RmtCommand ZeroPulse =
            new RmtCommand((ushort)(0.35 / MinPulse), true, (ushort)(0.8 / MinPulse), false);

        protected readonly RmtCommand ResCommand =
            new RmtCommand((ushort)(25 / MinPulse), false, (ushort)(26 / MinPulse), false);

        protected Color[] Pixels;
        private readonly int _gpioPin;

        public NeopixelChain(int gpioPin, uint size)
        {
            _gpioPin = gpioPin;

            Pixels = new Color[size];
            for (uint i = 0; i < size; ++i)
            {
                Pixels[i] = new Color();
            }
        }

        public void Update()
        {
            using (var commandList = new TransmitterChannel(_gpioPin))
            {
                ConfigureTransmitter(commandList);
                for (uint pixel = 0; pixel < Pixels.Length; ++pixel)
                {
                    SerializeColor(Pixels[pixel].G, commandList);
                    SerializeColor(Pixels[pixel].R, commandList);
                    SerializeColor(Pixels[pixel].B, commandList);
                }
                commandList.AddCommand(ResCommand); // RET
                commandList.Send(true);
            }
        }

        private void SerializeColor(byte b, TransmitterChannel commandList)
        {
            for (var i = 0; i < 8; ++i)
            {
                commandList.AddCommand(((b & (1u << 7)) != 0) ? OnePulse : ZeroPulse);
                b <<= 1;
            }
        }

        protected void ConfigureTransmitter(TransmitterChannel commandList)
        {
            commandList.CarrierEnabled = false;
            commandList.ClockDivider = ClockDivider;
            commandList.SourceClock = SourceClock.APB;
            commandList.IdleLevel = false;
            commandList.IsChannelIdle = true;
        }

        public Color this[uint i]
        {
            get => Pixels[i];
            set => Pixels[i] = value;
        }

        public void UpdateLed(byte r, byte g, byte b, uint index = 0)
        {
            this[index] = new Color() { R = r, G = g, B = b};
            Update();
        }
    }


    public class Color
    {
        public byte B;
        public byte G;
        public byte R;
    }


}