Apple Display Connector Adapter Board
I picked up an Apple Cinema Display at a garage sale for a few bucks. I noted that it had no apparent power connection, but the cable terminated in what appeared to be a DVI connector. Once I got it home, I realized that wasn’t the case. Not only was the connector not DVI, but it was a proprietary connector type called the Apple Display Connector (ADC) that carried digital video data in DVI format along with USB and power. Apple used it on late G3 and G4 Macintosh computers with an ADC video card. Several companies made adapters that supplied power, but they are rare these days and often expensive, such as this Apple-branded one on Amazon.
I looked for several options and found this DIY ADC Adapter article on Tony’s Look, It’s Another Blog. He hand-wired an adapter that worked, but I wanted to do it tidier and with a circuit board; also to improve my skills. Alex also wired a circuit board that he sells on BatchPCB, but in a related Instructable, he notes that he updated to version 1.1 to correct a wiring bug, yet the BatchPCB board appears to say “1.0″ on it (I tried contacting him but without success.) In addition, his version did not include VGA which I wanted to add, and I wanted an Altoids-tin ready board.
Oh, and I wanted to experiment with Open Source Hardware (OSHW) so the project is open-source. See the blog category for updates.
Update: (OK, I’ll make an exception.) I made a final version of the board that corrects the inconsequential ground wire error and you can can order it from BatchPCB here.
I’m curious: You mentioned the 1.0 vs 1.1 versions of the Alex_MP PCB; I ordered what I guessed would be the most current version – but mine also said 1.0 – but I received 2 boards. I would not have a clue how to design the layout, or what the electrical rules are, but since you have also designed your own, maybe you can shed some light on a problem with the Alex_MP board. I see where the USB needs to go to the ADC pins 21, 22 and 23; however, just because 22 and 23 say “Data-” and “Return” respectively, that doesn’t mean that they can occupy (intersect) the main ground path, correct? Wouldn’t that explain why the USB won’t work? It seems like an error that would be easy to make – that is, if it is actually an error? What do you think? Cause this is really driving me crazy. My display does work (finally) but the USB does not. I realize you didn’t design the board in question, I just thought you may have run into this issue in your design? Again, I really don’t know if it is the problem.
I’m not sure what the Alex_MP board is like since I never bought one. If I remember correctly, USB has a differential data path, so you can’t connect either of the data pins to ground nor +5V. ADC pin 23, “Return” is the 0V reference for the 5V power, so it’s at the same potential as electrical ground and can safely be connected.
ADC pin 21 should be connected to USB data + and pin 22 should be connected to USB data – (and not to ground). On my board, that’s the way they are connected and that permits the USB hub feature of my monitor to work (although as I note, it’s not “seen” by the system, not even in Apple System Profiler.)
A source for ADC connectors
http://www.surplussales.com/Connectors/Video-Data.html