Add README for repo

Documentation/README.md

+# Resources
+
+See the following resources to get started.
+
+## .NET Core
+
+* [.NET Core documentation](https://docs.microsoft.com/dotnet/)
+* [Install .NET Core on Raspberry Pi](https://github.com/dotnet/core/blob/master/samples/RaspberryPiInstructions.md)
+* [.NET Core ARM64 Status](https://github.com/dotnet/announcements/issues/82)
+
+## Raspberry Pi
+
+* [Enable SPI on Raspberry Pi](https://www.raspberrypi-spy.co.uk/2014/08/enabling-the-spi-interface-on-the-raspberry-pi/)
+* [Enable headless Raspberry Pi](https://hackernoon.com/raspberry-pi-headless-install-462ccabd75d0)
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README.md

-# iot
-This repo includes implementations for various boards, chips and PCBs to enable .NET to be used for IoT scenarios.
+# .NET Core IoT Libraries
+
+.NET Core can be used to build applications for [IoT](https://en.wikipedia.org/wiki/Internet_of_things) devices and scenarios. IoT applications typically interact with sensors, displays and input devices that require the use of [GPIO pins](https://en.wikipedia.org/wiki/General-purpose_input/output), serial ports or similar hardware.
+
+This repository contains the [System.Devices.Gpio](https://dotnet.myget.org/feed/dotnet-corefxlab/package/nuget/System.Devices.Gpio) library and implementations for various boards like [Raspberry Pi](https://www.raspberrypi.org/) and [Hummingboard](https://www.solid-run.com/nxp-family/hummingboard/).
+
+It also contains a growing set of community-maintained bindings for IoT components, like the [Mcp3008](https://www.adafruit.com/product/856) ([bindings](src/Mcp3008/Mcp3008.cs)), for example.
+
+Note: System.Device.Gpio is in early preview. It is not yet supported and will continue to change.
+
+## Install .NET Core
+
+* [Official releases](https://www.microsoft.com/net/download)
+* [Daily builds](https://github.com/dotnet/core/blob/master/daily-builds.md)
+
+## Contributing
+
+Please contribute. We are primarily interested in the following:
+
+* Improving quality and capability of the drivers for supported boards.
+* Implementations for additional boards
+* .NET bindings for a wide variety of sensors, chips, displays and other components.
+
+## License
+
+.NET Core (including the iot repo) is licensed under the [MIT license](LICENSE).

src/Mcp3008/Mcp3008.cs

+using System;
+using System.Devices.Gpio;
+using System.Devices.Spi;
+
+public class Mcp3008
+{
+
+    private SpiDevice _spiDevice;
+    private GpioPin _CLK;
+    private GpioPin _MISO;
+    private GpioPin _MOSI;
+    private GpioPin _CS;
+
+
+    public Mcp3008(SpiDevice spiDevice)
+    {
+        _spiDevice = spiDevice;
+    }
+
+    public Mcp3008(GpioController controller, int CLK, int MISO, int MOSI, int CS)
+    {
+        _CLK = controller.OpenPin(CLK, PinMode.Output);
+        _MISO = controller.OpenPin(MISO, PinMode.Input);
+        _MOSI = controller.OpenPin(MOSI, PinMode.Output);
+        _CS = controller.OpenPin(CS, PinMode.Output);
+    }
+
+    public int Read(int adc_channel)
+    {
+        if (adc_channel < 0 && adc_channel > 7)
+        {
+            throw new ArgumentException("ADC channel must be within 0-7 range.");
+        }
+
+        if (_spiDevice != null)
+        {
+            return ReadSpi(adc_channel);
+        }
+        else
+        {
+            return ReadGpio(adc_channel);
+        }
+    }
+
+    private int ReadGpio(int adc_channel)
+    {
+        //port of https://gist.github.com/ladyada/3151375
+
+        while (true)
+        {
+            var commandout = 0;
+            var trim_pot = 0;
+
+
+            _CS.Write(PinValue.High);
+            _CLK.Write(PinValue.Low);
+            _CS.Write(PinValue.Low);
+
+            commandout |= 0x18;
+            commandout <<= 3;
+
+            for (var i = 0; i < 5; i++)
+            {
+                if ((commandout & 0x80) > 0)
+                {
+                    _MOSI.Write(PinValue.High);
+                }
+                else
+                {
+                    _MOSI.Write(PinValue.Low);
+                }
+
+                commandout <<= 1;
+                _CLK.Write(PinValue.High);
+                _CLK.Write(PinValue.Low);
+            }
+
+            for (var i = 0; i < 12; i++)
+            {
+                _CLK.Write(PinValue.High);
+                _CLK.Write(PinValue.Low);
+                trim_pot <<= 1;
+
+                if (_MISO.Read() == PinValue.High)
+                {
+                    trim_pot |= 0x1;
+                }
+            }
+
+            _CS.Write(PinValue.High);
+
+            trim_pot >>= 1;
+            //var pot_adjust = Math.Abs(trim_pot - last_read);
+            return trim_pot;
+        }
+    }
+
+    private int ReadSpi(int adc_channel)
+    {
+        // ported code from:
+        // https://github.com/adafruit/Adafruit_Python_MCP3008/blob/master/Adafruit_MCP3008/MCP3008.py
+
+        int command = 0b11 << 6;                  //Start bit, single channel read
+        command |= (adc_channel & 0x07) << 3;  // Channel number (in 3 bits)
+        var input = new Byte[] { (Byte)command, 0, 0 };
+        var output = new Byte[3];
+        _spiDevice.TransferFullDuplex(input, output);
+
+        var result = (output[0] & 0x01) << 9;
+        result |= (output[1] & 0xFF) << 1;
+        result |= (output[2] & 0x80) >> 7;
+        result = result & 0x3FF;
+        return result;
+    }
+}
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