Anyone know how to make one of these? I see them on eBay but I don't really want to pay like $30 for one. Anyone have a schematic or anything?
Probably has some logic in it, not a simple device. I would guess it could be built but not without some custom chip programming.
Those adapters perform a fairly complicated set of transformations, both electrical (supporting an ADB port on one side and USB target interface on the other) and protocol (converting ADB keyboard codes to USB HID data). They're not just wires pasted together. To make your own you'll need a USB-equipped microcontroller (as cheap as a few bucks each in quantity, but more like $15-$20 for quantity one), a few discrete components to fake up an electrically-compliant subset of an ADB port, and a fairly intricate bit of software to run the whole mess.
If your time is worth *anything* making your own will cost you a lot more then $30. There are oodles of schematics Google-able out there for doing similar projects with PS/2 keyboard ports, but good luck finding sufficient documentation on ADB to boil one up.
Searching completed auctions turns up a number of ADB-USB adapters that sold for less than that, and several what sold for under $20. A bit of patience and you'll have your adapter for a price (I expect) you can afford. Heck, recently an iMate _with_ an ADB keyboard went for US$5!
Here's a USB/ADB adapter I've got that came with a Kensington USB mouse, similar to the PS/2 adapters that came with most USB mice. Probably the opposite direction of the connection you're looking for, but I assume it has all the circuitry you guys are describing also, although, it's significantly smaller than a Griffin iMate, isn't it? Or does going in the opposite direction require less or no chip circuitry?
I assume it has all the circuitry you guys are describing also, although, it's significantly smaller than a Griffin iMate, isn't it? Or does going in the opposite direction require less or no chip circuitry?
That's a passive plug adapter. It changes pinouts, for devices that can output both signals, but lacks any ability to convert one type of signal to another.
So, if I plug any other USB mouse into it, it's not going to work? Well, that's interesting. Then that Kensington USB mouse was a lot more unique than I had thought. It must have been one of the only USB devices capable of ADB too. I found it in a box full of ADB stuff someone was throwing away. I tossed it. It was a two buttom roller mouse and I couldn't see how it could be any better than a regular ADB mouse like the Macally two button mouse. I wonder who Kensington had in mind as the target consumer? Someone with an ADB Mac who planned on getting an iMac in the future? Or else, the Kensington mouse software was exceptionally good enough to attract people still on ADB to buy a new mouse.
Probably more likely it was cheaper to just produce the one line of mice rather than two, and throw the adapter in the box for free, in the period when ADB machines were still current and USB was coming in. And it would have made it a no-brainer for the consumer.