#Purpose

• This program lets your Raspberry Pi control control RGB LEDs.

#Features

1. Color correction. Some RGB LED strips have imbalanced LEDs, and this program allows you compensate by reducing brightness on any color channel.

2. Simple file-based API. During continuous operation, simply put your desired target color into a CSV file containing RGB values ranging from 0-255, and the program will implement your target color. Change it as often as you like.

3. Transition options. You can fade from the current color to the target color directly, by fading to black and then fading to the target color, or by changing to the target color instantaneously. You can change these preferences on the fly.

4. Integration with openHAB via the exec binding.

#HOWTO

##What You Need

1. Raspberry Pi (Rev B tested, but any revision should work.)

2. An RGB LED strip (I bought this one, but any 4-pin common-anode RGB LED strip will work. Deviations will work, but you'll need to come up with your own wiring diagram.)

3. A DC power supply (My strip is 12VDC, with a maximum current of 0.6A, and I have a 12VDC 8.5A power supply.)

4. Three MOSFETs (I used these N-channel MOSFETs. Deviations can work, but you'll need to come up with your own wiring diagram.)

5. Three free GPIO pins

6. At least 60% available CPU on your Pi

7. Basic Linux skills (package installing, file copying and editing, running commands)

##Hardware Setup

1. Wire up your MOSFETs and RGB LED strip as you see on the first diagram in this Adafruit tutorial for the Arduino, except that:

   1. You have a Pi, not an Arduino, but the basic principle is the same.

   2. You power the LED strip with your dedicated power supply, not any pin from the Pi.

   3. You will run a ground wire from your Pi to the ground terminal of the power supply.

   4. Pick three GPIO pins to control red, green, and blue. Read the pigpio documentation carefully before picking your pins. If you get this wrong, various bad things can happen.

##Software Setup

1. As shown here, download, build, and install pigpio on your Raspberry Pi, then start the pigpio daemon.

   1. Download, build, and install.

        wget abyz.co.uk/rpi/pigpio/pigpio.zip
        unzip pigpio.zip
        cd PIGPIO
        make
        make install
      

   2. Start the pigpio daemon.

        sudo pigpiod
      

2. Install, configure, and run Hugh.

   1. Copy the Hugh directory tree to your Pi. Mine is in /home/pi/hugh

   2. Edit hugh_config.ini to match the BCM-indexed GPIO pins that you chose above.

   3. Run Hugh from its directory:

        cd /home/pi/hugh
        sudo python ./hugh.py
      

   4. Any edits to the files hugh_config.ini or rgb will be loaded and quickly implemented by Hugh.

##openHAB Integration (optional)

• My solution builds on this example for KNX and this example using MQTT.

###items

1. Add this Color item to any of your *.items files, which gives you a color picker UI.

    Color  HSB   "Color Light"   <slider>  (Lights)
   

2. Add a String item to any of your *.items files, as your interface to the Hugh software running on your Pi.

   1. If the Pi running Hugh is also your openHAB server, add this:

      String RGB "RGB Value" { exec=">[*:echo %2$s > /home/pi/hugh/rgb]" }

   2. Otherwise, add this entry:

      String RGB "RGB Value" { exec=">[*:ssh pi@pi2 echo %2$s > /home/pi/hugh/rgb]" }

3. DON'T put RGB item into any groups or sitemaps. It's not something that users should directly interact with.

4. Put the HSB item into any groups and sitemaps you prefer. The reference example assumes you want it in the Lights group.

5. Edit the RGB item to match the device name, username, and target directory for Hugh's RGB file.

###rules

1. Add this rule to any of your *.rules files. This converts the HSB (hue, saturation, brightness) color to comma-separated RGB (red, green, blue) values, and puts them into the RGB String item, which in turn gives the RGB values to Hugh.

    rule "Set RGB Value from HSB"
    when
    	Item HSB changed
    then
    	var HSBType hsbValue = HSB.state as HSBType 
    
    	// scale the values to 256 levels
    	var int red = Math::round(hsbValue.red.floatValue * 2.55)
    	var int green = Math::round(hsbValue.green.floatValue * 2.55)
    	var int blue = Math::round(hsbValue.blue.floatValue * 2.55)
    
    	sendCommand(RGB, red+","+green+","+blue)
    	postUpdate(RGB, red+","+green+","+blue)
    end
   

###SSH

1. If the Pi running Hugh is also your openHAB server, then you can skip this step. Otherwise:

   1. As the root user, generate an SSH keypair on your openHAB server with an empty passphrase.

   2. On the Pi, as a regular user (e.g. pi), append the public key to ~/.ssh/authorized_keys in the user account on the Pi (e.g. /home/pi/.ssh/authorized_keys) to allow your openHAB server to automatically log in when it runs ssh via the exec binding in the RGB item.

###usage

• openHAB will pick up on the items and rules changes. You should be able to interact with the HSB color picker in any openHAB UI and see the color reproduced by your RGB LEDs.