Quick .Net api#

 //REF: https://github.com/travisgoodspeed/PyMetaWatch/blob/master/pymw.py

    public class MetaWatchProtocol
    {
        public static byte[] BuildMessage()
        {
            //TEST:
            return null;
        }

        enum ScreenMode { MODE_IDLE = 0, MODE_APPLICATION = 1, MODE_NOTIFICATION = 2, MODE_SCROLL = 3 };
        enum StatusChange {STATUS_CHANGE_MODE = 0, STATUS_CHANGE_DISPLAYIMEOUT = 1};
        enum Button { A=0, B=1, C=2, D=3, E=5, F=6 };
        enum ButtonType { Immediate = 0, PressAndRelease = 1, HoldAndRelease = 2, LongHoldAndRelease = 3 };

        // Time to pause between packets
        //#_TX_PACKET_WAIT_SEC = 0.025 #per Javier's empirical values.
        float _TX_PACKET_WAIT_SEC = 0.2f;
        //#_TX_PACKET_WAIT_SEC = 0.1   #per Goodspeed's less optimistic values.

        #region CRC
        class CRC_CCITT
        {
            // Implementation of CRC-16-CCITT

            bool inverted = true;
            static uint[] table = null;
            static uint[] flipmask = {0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15};

            public CRC_CCITT()
            {
                init();
            }

            void init()
            {
                if (null != table)
                    return;

                uint crc = 0xFFFF;          // initial value
                const uint polynomial = 0x1021;   // 0001 0000 0010 0001  (0, 5, 12) 
                table = new uint[256];
                uint c;
                for (uint idx = 0; idx < table.Length; idx++)
                {
                    crc = 0;
                    c = idx << 8;
                    for(int j=0; j<8; j++)
                        if (0x8000 == ((crc^c) & 0x8000))
                            crc = (crc<<1)^polynomial;
                        else
                            crc <<= 1;
                    c <<= 1;
                    crc &= 0xFFFF;
                    table[idx] = crc;
                }
            }

            
            public uint update_crc(uint crc, uint c)
            {
                c = 0x00ff & (c % 256);
                if (inverted)
                    c = flip(c);
                
                uint tmp = ((crc >> 8) ^ c) & 0xffff;
                crc = (((crc << 8) ^ table[tmp])) & 0xffff;
                return crc;
            }

            public uint checksum(byte[] bytes)
            {
                uint v = 0xFFFF;
                for(int i=0; i< bytes.Length - 2; i++)
                    v = update_crc(v, (uint)bytes[i]);
                return v;
            }

            uint flip( uint c)
            {
                // MetaWatch/Fossil requires bitflipping
                return (flipmask[c & 0x0F] << 4) + flipmask[ (c & 0xF0) >> 4 ];
            }
        }
        #endregion

        public string SetDisplayInverted(bool value)
        {
            return value ? "\x41\x00\x00\x01" : "\x41\x00\x00\x00";
        }

        public byte[] Buzz()
        {
            return Buzz( 500, 500, 1);
        }
        public byte[] Buzz( int millisecOn, int millisecOff, int cycles )
        {
            //Buzz the buzzer.
            return new byte[] { 0x23, 0x00, 0x01, 
                             (byte)(millisecOn >> 8), (byte)(millisecOn & 0xFF),
                             (byte)(millisecOff >> 8), (byte)(millisecOff & 0xFF),
                             (byte)(cycles & 0xFF )
                         };
        }

        CRC_CCITT CRC = new CRC_CCITT();

        public byte[] BuildMessage( byte[] cmd )
        {
            byte[] sendbuf = new byte[4 + cmd.Length];
            sendbuf[0] = 0x01;
            sendbuf[1] = (byte)((cmd.Length + 4) & 0xFF);
            Buffer.BlockCopy(cmd, 0, sendbuf, 2, cmd.Length);
            uint crc = CRC.checksum(sendbuf);
            //Little Endian
            sendbuf[sendbuf.Length-2] = (byte)(crc & 0xFF);
            sendbuf[sendbuf.Length-1] = (byte)(crc >> 8);
            return sendbuf;
        }
    }

void Talk()
        {
            BluetoothAdapter bluetooth = BluetoothAdapter.DefaultAdapter;
            if (!bluetooth.IsEnabled)
                bluetooth.Enable();

            ICollection<BluetoothDevice> devices = bluetooth.BondedDevices;
            foreach (BluetoothDevice device in devices)
            {
                if (device.Name.Contains("Watch"))
                {
                    BluetoothSocket socket = device.CreateRfcommSocketToServiceRecord(Java.Util.UUID.FromString("00001101-0000-1000-8000-00805F9B34FB"));
                    socket.Connect();
                    try
                    {
                        MetaWatchProtocol protocol = new MetaWatchProtocol();
                        byte[] message = protocol.BuildMessage(protocol.Buzz());
                        socket.OutputStream.Write( message, 0, message.Length);
                        socket.OutputStream.Flush();

                    }
                    finally
                    {
                        socket.Close();
                    }
                }
            }
        }