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geekhack Community => Keyboards => Topic started by: fohat.digs on Thu, 06 March 2014, 08:10:41
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I have a number of adapters and converters, and I use them without really understanding what they do.
For ADB-to-USB converters for old Apples, I know that circuitry is require to actually change the signals.
As I understand it, AT-to-PS/2 adapters are usually just pass-through wiring to change plug size.
But, in simple layman's terms, do the PS/2-to-USB adapters do? I am a smart guy, but I have never tried to understand what is going on electronically inside them.
I have had near-100% success with the cheapest simplest PS/2-to-USB adapters with a variety of keyboards, but other people seem to have loads of problems unless they use the more complicated and expensive ones. What, for example, does a Blue Cube do, electrically, that a $1 Chinese Y-cable does not?
Where I want to go with this is to change some of my attached PS/2 keyboard cables to USB, and wondering how to avoid the kludge of concealing wires, plugs, adapters, and/or converters inside the case so that only a simple USB cable emerges.
Thanks for keeping it simple.
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There are active PS/2 to USB adapters and passive ones. In order for the passive adapters to work, the mouse or keyboard has to have special circuitry inside. Those little green (passive) adapters included with your mouse will *only* work with a mouse with this special circuitry, and not just any mouse.
Microsoft has such circuitry and is very protective of it. Just Google "microsoft u2 lawsuit" and you'll see.
I recently had an interesting experience here with an active (Trendnet) PS/2 to USB adapter. When I used it with 2 different brand of trackball I was getting phantom right mouse clicks & scroll wheel movement (just one notch). I replaced it with one from Ziotek and all is fine now.
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Thanks for the reply.
I have never had a mouse issue and have mostly used USB mice for a decade or so.
My conceptual question is what does an "active" converter actually do?
And why have the passive ones always worked for me, with literally dozens of different keyboards, some quite old?
And, lastly, does "passive" actually mean "does nothing" so that I can simply cut and splice wire from the controller to USB?
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Hello good sir!
I believe I have a found a document that will help you understand the underlying science behind said converters.
Here it is:
https://mega.co.nz/#!kIdUzQJR!IHcbhqdGM8NizlXwdTxeDdUjG4lMZhHt981IaG86WCY
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I have a number of adapters and converters, and I use them without really understanding what they do.
For ADB-to-USB converters for old Apples, I know that circuitry is require to actually change the signals.
As I understand it, AT-to-PS/2 adapters are usually just pass-through wiring to change plug size.
But, in simple layman's terms, do the PS/2-to-USB adapters do? I am a smart guy, but I have never tried to understand what is going on electronically inside them.
I have had near-100% success with the cheapest simplest PS/2-to-USB adapters with a variety of keyboards, but other people seem to have loads of problems unless they use the more complicated and expensive ones. What, for example, does a Blue Cube do, electrically, that a $1 Chinese Y-cable does not?
Where I want to go with this is to change some of my attached PS/2 keyboard cables to USB, and wondering how to avoid the kludge of concealing wires, plugs, adapters, and/or converters inside the case so that only a simple USB cable emerges.
Thanks for keeping it simple.
i would be one of the few i guess that has minor issues with adapters.............
my ziotek works like a charm on all my ps2 boards
my purple ended one (see below) does not and my belkin died, so i give up :-\
the generic one will not power my model m at all, my dell 101's at times, but most of the other ones fine
i run win 7 on my one desktop and win 8 on the other
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Thanks for the reply.
I have never had a mouse issue and have mostly used USB mice for a decade or so.
My conceptual question is what does an "active" converter actually do?
And why have the passive ones always worked for me, with literally dozens of different keyboards, some quite old?
And, lastly, does "passive" actually mean "does nothing" so that I can simply cut and splice wire from the controller to USB?
Passive can man that it "does nothing". Usually this is the case, it just adapts the size/shape. However, I would say that a passive convert is simply one without an "active" (or powered) device, usually a microcontroller.
Some keyboards need what is called a pull-up resistor. If your adapter just includes this item, then it will be passive but also doing something.
I have had a few of the cheap USB-to-PS2 adapters and the biggest issue I had with them is that they "reset" randomly, at least once every few hours. The more expensive ones (ID innovations, xkeys "y mouse", and possibly the blue cube) will generally not have this issue.
Also cheap ones will only support 2KRO, whereas more expensive ones (ID innovations, soarer) will support at least 6KRO.
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Good, thanks.
I think I have about 50 1K ohm .25 watt resistors that I got for use with my Teensies. So, my first experiment with be to cut and splice the wires from a PS/2 keyboard (with resistors between Vcc and data and clock) straight to a USB cable, if I can find the USB pin-out, which now I can't recall ever having seen .....
There is room for that inside even the tightest case.
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For PS/2 to USB, it's the same thing as ADB to USB. It's changing all the signals actively. The only difference is that PS/2 is more well known. When they're saying that there is 'special circuitry' for passive adapters, all it means is that for devices which can use them they recognize which protocol they are plugged into, and use that language. Not all do. When on the other hand it's an active converter, it acts like a translator. On the computer side it acts like a normal usb device, since usb is polling based, it polls the device and asks for any changes however fast the connection is set. On the device side it thinks it is talking to its native bus device (the convertor/translator) in its native language. So the ADB or PS/2 keyboard thinks that it is connected to a computer in its usual setting - PS/2 is interrupt-based, so when something happens it makes what it's talking to stop what it is doing and listen to its updated information - in this case the convertor. At this point the convertor translates and creates usb packets which are picked up when the computer polls what it sees as the USB device. Most of that's probably identical for ADB, PS/2 and things like soarer's convertor.
Also that's exactly what AT-to-PS/2 does. When IBM changed from XT to AT they changed the signal, but not the plug. When they changed to PS/2 they made the plug smaller but kept the signal/protocol identical. I have no idea why they went from 5 pins to 6 though, because obviously the 6th pin can't do anything useful because they were without it when the protocol was made.
If you don't game, that's the reason why you've not had a problem with the cheap ones. I had a cheap one and couldn't walk and do anything else at the same time - it was built only for typing. I looked at what it was doing using aquakey test, and what it did was send a key up for *everything* whenever just one key was released. Obviously completely useless for holding down anything while doing other stuff.
The blue cube and certain belkin converters are known to be able to do at least 6KRO and are able to keep up with anything the PS/2 keyboards can do otherwise. No reinitializing (time when no input can be done while it does so) or anything, just solid conversion. They are also known for being able to power more demanding things such as the model m. This is why when ripster wanted to do what you want to do, he would open a blue cube up and solder it inside a keyboard so that it would physically seem to be just a USB device. Maybe you can find his guide for that somewhere.