# HG changeset patch
# User Tero Marttila <terom@fixme.fi>
# Date 1311709421 -10800
# Node ID 3803c0b40a9c7b294c9c7f5bb61e6450ba95decf
# Parent  0d0309787be360c4d43f5460fe48b585acc8c330
docs: own dmx writeup

diff -r 0d0309787be3 -r 3803c0b40a9c docs/dmx.txt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/docs/dmx.txt	Tue Jul 26 22:43:41 2011 +0300
@@ -0,0 +1,53 @@
+* 250 kHz clock
+    * 250000 bits / s
+    * 4µs / bit
+* idle line = high (transmitter/master drives line high)
+
+        
+
+Packet structure:
+
+* paket format
+    * break
+    * mark (MAB)
+    * 2-512 frames
+        * frame 0 = start code = 0x00
+        * frame N = channel N = 0-255
+        * 1 start bit, 8 data bits, 2 stop bits, no parity
+        * mark (MTBF)
+    * mark (MTAP)
+
+* break
+    * syncs start of DMX packet
+    * >= 22 low bits (88 µs)
+    * up to 1s
+    * recommended 25 - 30 low bits
+
+* mark after break (MAB)
+    * immediately follows the break
+    * high mark of > 2 bits (8µs)
+    * up to 1s
+    * recommended 3 high bits
+
+* (channel frames)
+    * first frame is start code (SC)
+        * data value = 0x00 signifies dimmer data
+
+    * 11 bits / frame
+        * 1 low bit (start bit)
+        * 8 data bits (0-255)
+        * 2 high bits (stop bits)
+ 
+    * mark time between frames (MTBF)
+        * idle time between frames; line kept high
+        * can be as short as desired
+
+    * between 1 and 512 sequential frames
+
+* mark time between packets (MTBP)
+    * after the last frame's stop bits
+    * same as MTBF
+    * idle time between packets; line kept high
+    * can be as short as desired
+
+