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geekhack Community => Keyboards => Topic started by: hyperlinked on Sat, 07 November 2009, 20:58:46

Title: Mini DIN 8 vs ADB to USB Convertors?
Post by: hyperlinked on Sat, 07 November 2009, 20:58:46

I've come across a number of references here about the relatively high cost of getting iMate adapters to convert ADB cables to USB so you can use an AEKII on modern machines. It's been a while since I've fumbled with old Apple ADB cables, but I seem to remember that a male mini DIN 4 plug fit fine into a female mini DIN 8 plug.

If my memory serves me true, then shouldn't you be able to buy a mini DIN 8 to USB connector if you can't find a reasonably prices iMate? They've got them here:
http://store.microconnectors.com/servlet/-strse-1186/USB-to-2-Port/Detail

The convertor would still cost more than most AEKII's on eBay, but wouldn't be twice as much.

Title: Mini DIN 8 vs ADB to USB Convertors?
Post by: ak_nala on Sun, 08 November 2009, 02:55:03

Wow, interesting thought, but pretty sure there's no way it would work.

Don't know about the pin-for-pin compatibility (data, power, ground), but though they are both part of the mini-DIN family and the pin layout looks more or less the same, there is a key in the ADB plug that would prevent insertion into the serial adapter. (Note that ADB cables are basically identical to S-Video cables.)

The real problem is that there is a whole lot that needs to go on to communicate to an ADB device that is normally done by the host computer. The iMate takes care of that communication, while a normal serial adapter wouldn't know where to start.

Same goes with trying to hack a PS/2 to USB adapter to work with ADB. They just don't speak the same language. ADB was invented by the Woz to be a better solution for its intended purpose and is a very different beast to standard PC serial protocols and PS/2.

For starters, ADB is a bus architecture and all communication on that bus is instigated by the host computer (which does periodic polling of the devices detected at startup for status updates), while with PS/2 either the keyboard or the computer can instigate communication by manipulating the clock line, IIRC. ADB doesn't even HAVE a clock line.

So the iMate has to mimic a host computer as well as translate the ADB protocols to USB in both directions. Bit more complicated than a Blue Cube or a serial Adapter.