Turn AV32R AC3 input into SP/DIF input?

canavan

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Has anyone here ever thought about turning the second digital output / AC-3 input into another SP/DIF input? I'd assume that the AC3-RF board does nothing but turn AC3-RF into a normal SP/DIF signal. Additionally, I'd think that it doesn't even have a mechanism to announce its presence, since one has to change jumpers elsewhere on the mainboard to make the card accessible. If things actually are that easy, all one would have to do would be to connect the input signal and ground pins of the AV32R mainboard with the output signal and ground (and pull the mute signal to 5V or gnd, depending on if it is GND or !GND) to get another input. I have a AC3-RF board, but no LD-Player for testing. If anyone has a Laserdisc player, an AV32R, a scope and some spare time, I'll pay for shipping the AC3 card both ways.
 
I've just got all the required bits and pieces (Laserdisc player, AC3-Laserdisc, software scope incluing windows PC, windows, software etc...) together last friday. There's good news and bad news. The good news iis that all except one pin of the AC3-RF board are easy to map, mosty because there are neatly labled test vias all over the board), the bad news is that the board generates TTL-Level SP/DIF style signals, i.e. 5V instead of 0.5V. The pinout of the board is as follows, assuming the same orientation as in the picture here http://www.avforums.com/forums/10160060-post5.html

Code:
Gnd     o  o   oscon 
sreset  o  o   unknown
Mute    o  o   Ac3Out
Gnd     o  o   Gnd
AC3In   o  o   Gnd
Gnd     o  o   Gnd
N5V     o  o   P5V
N5V     o  o   P5V

oscon is pulled to 5V

unknown is pulled to Gnd

Mute is 5V if no valid signal is present, Gnd otherwise

sreset is pulled to ground (by the AVR) during powerup or reset of the AV32R

AC3In is directly connected to the center pin of the AC3In conector on the back if the switch is in the proper position

Converting the signal is actually quite simple, as described in epanorama.net/S/PDIF Interface

In the screenshot blow, channel 1 (yellow) is the signal on AC3Out of the AC3-RF board, channel 2 (green) is the signal on the AV32R's remaining SP/DIF out.
 

Attachments

  • ac3board3.png
    ac3board3.png
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I finally found the time to solder a prototype, and so far, it's working flawlessly - except of course for the fact that the firmware doesn't allow the trigger switches to be programmed for the AC3-RF input.
 

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