DMX512 to D54 Converter

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I created this project to help interface Mintor DMX console to Strand EC90 dimmer which uses D54 analog protocol,

This's the project link: http://www.avrfreaks.net/index.php?module=Freaks%20Academy&func=viewItem&item_type=project&item_id=2866

The only D54 available data I found was Wikipedia which is based on old Strand doc. I updated wikipedia D54 topic according what I found later after I finished.

This's the wikipedia link after update:
http://en.wikipedia.org/wiki/D54_%28protocol%29

You may notice that +-12 volt path is not regulated, that's because I only want +-5 volt signal swing & LF353 has very high supply rejection ratio.

In the forums I found someone asking how to produce negative voltage from AVR (I can't remember where),

I produced -5 volt sync signal using 2 transistors connected to pin PC7,
When PC7 is low => Q2 collector will give -5 volts, When PC7 is high => Q2 collector will give 0 volts.
This works fine to this project.
There may be a better way, I'd like to know about.

In the schematic U3 is symbolized as a connector it's 8 pin DIL IC SN75176B, but it's not found in my schematic capture software, so I used 8 pin connector instead.

Sooner I'll post another version of the firmware reads DMX without using USART.

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I did this about 20 years ago! I can't remember there being much magic about D54, it was much like a video signal and similar to AMX192 which was the precursor to DMX512.

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Quote:
I did this about 20 years ago!

You are an expert, I hope someday be in your experience
The whole project was easy to me to implement.

Quote:
I can't remember there being much magic about D54

You are right it's not hard to get it, but my problem was to find data about it, may be 20 years ago there was available data about it as strand itself was on.

The dimmer I worked with doesn't fully accept the timing mentioned in wikipedia until I enlarged the sync. signal.

Quote:
it was much like a video signal

Yes it is, & it was not a problem to deal with, just I found somewhere in archives someone asking about the negative out from MCU, & I thought it may help to talk about it.

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I cannot remember how exacty I did the output. I recall I used a monostable to generate tbe channel sync that was triggered when the DAC was written to and the frame sync was generated by the micro. There was a handful of transistors in the output stage. Unfortunately I have no copies of the circuitry or the code I wrote ( in Z80 assembler).

Good to hear you got it working.