Add Hummingboard GPIO node

hardware/HummingboardGPIO/README.md

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+node-red-node-hbgpio
+====================
+
+A <a href="http://nodered.org" target="_new">Node-RED</a> node to read and write the digital IO of a SolidRun HummingBoard.
+
+Install
+-------
+
+Run the following command in the root directory of your Node-RED install:
+
+    npm install node-red-node-hpgpio
+
+**Note :** This **should** be run as root in order to move and set SUID permissions on a script to talk to the gpio pins. Alternatively you can run as a normal user and then move the file and change permissions manually.
+
+    sudo cp node_modules/node-red-node-hpgpio/gpiohb /usr/local/bin/
+    sudo chmod 4755 /usr/lcoal/bin/gpiohb
+
+
+Usage
+-----
+
+Hummingboard GPIO input and output nodes.
+
+This requires a small script (gpiohb) to run as root in order to work. It should be placed in /usr/local/bin/ and have SUID permissions 4755.
+
+**Note:** We are using the actual physical pin numbers as they are easier to locate.
+
+###Output node
+
+Expects a <b>msg.payload</b> with either a 0 or 1 (or true or false).
+
+Will set the selected physical pin high or low depending on the value passed in.
+
+The initial value of the pin at deploy time can also be set to 0 or 1.
+
+
+###Input node
+
+Generates a **msg.payload** with either a 0 or 1 depending on the state of the input pin.
+
+The **msg.topic** is set to **pin/{the pin number}**
+
+**Note:** The input node waits for a change on the level of the pin before reading the value - and then resets to wait for the next interrupt - so it is possible to miss very fast changes as we may still be reading the value when the second edge occurs.