Added DisplayBacklight blog post

input/blog/2017/2017_05_13_display_backlight.md

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+title: Blog
+post: DisplayBacklight
+date: 2017-05-13
+comments: true
+flattr: true
+github: https://github.com/xythobuz/DisplayBacklight
+parent: projects
+position: 100
+---
+
+## {{ page["post"] }}
+<!--%
+from datetime import datetime
+date = datetime.strptime(page["date"], "%Y-%m-%d").strftime("%B %d, %Y")
+print "*Posted at %s.*" % date
+%-->
+
+DisplayBacklight is an Ambilight-clone made with an Arduino controlled by a macOS machine.
+
+<div class="lightgallery">
+    <a href="https://www.youtube.com/watch?v=Sy3Wgt9CKz4">
+        <img src="http://img.youtube.com/vi/Sy3Wgt9CKz4/0.jpg" alt="DisplayBacklight - macOS Arduino Ambilight">
+    </a>
+    <a href="img/ambilight-1.jpg">
+        <img src="img/ambilight-1_small.jpg" alt="Photo 1">
+    </a>
+    <a href="img/ambilight-2.jpg">
+        <img src="img/ambilight-2_small.jpg" alt="Photo 2">
+    </a>
+</div>
+
+### Hardware
+
+The software currently only supports driving RGB-LEDs with the colors from the edge of a screen, so you have to place an RGB LED strip on the outer edges of your computer monitors. Multiple screens are supported using a single LED strip for all of them.
+
+You need an LED strip with individually addressable LEDs like the popular [WS2812 RGB LED strips](https://www.sparkfun.com/products/12025). The data line is connected to pin 2 of the Arduino. The [Adafruit Neo-Pixel library](https://github.com/adafruit/Adafruit_NeoPixel) is used to control the LEDs.
+
+### Protocol
+
+The color data is transmitted using the serial port and the USB-UART converter built into most Arduinos. Communication happens at 115200bps, the LED count is hardcoded in both firmware and host software. First, a magic string, also hardcoded, is sent, followed by 3 bytes containing Red, Green and Blue, for each LED. When the last byte has been received the whole strip is refreshed at once.
+
+### Software
+
+The macOS host software is opening the connection to the serial port, grabbing a screenshot, processing the edges to calculate each LED color and finally sending it to the device.
+
+<div class="lightgallery">
+    <a href="img/ambilight-3.png">
+        <img src="img/ambilight-3.png" alt="Screenshot">
+    </a>
+</div>
+
+### License
+
+DisplayBacklight itself is made by Thomas Buck <xythobuz@xythobuz.de> and released under a BSD 2-Clause License. See the accompanying COPYING file.
+