DMX 512
How to receive
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Receiving DMX 512 is very easy. The basic Idea is to set the UART in 9 bit mode, and look at the ninth bit. If it is a "0" we are still in the "Make before break" if it is "1" we have a valid data byte. Data bytes are always counted from the second byte received, as the first is the start code (usually 00H, although the specifications say this is for dimmers, I am yet to see any other start code used)
Following is a schematic for receiving DMX 512 with an 8051 (using my favorite SN75176 RS 485 receiver chip). I have also provided a sample source code, Please note it only decodes the first 256 channels, to decode the second 256 you will need to add another switch, and re work the channel detection section of the source code. I will further comment the code when I have time.
This schematic was produced under protel and converted over to a gif.
Here is the ASM source code to receive DMX 512.