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geekhack Projects => Making Stuff Together! => Topic started by: snhstq on Sat, 16 November 2013, 00:46:39

Title: IBM 3278 to PS/2 interface
Post by: snhstq on Sat, 16 November 2013, 00:46:39

Hi,

You all  know that the model M  is one of the best keyboard ever produced.

(http://clickykeyboard.com/2012/mar24/010.jpg)

The buckling spring technology used in this keyboard is only surpassed by the beam spring technology used by IBM in their IBM 3277 and 3278/79 keyboards.
Unfortunately these keybaords have a parallel interface via a DB25 connecter and can't be connected with a IBM PC.
I have developed with a ATmega48/88/168 interface which converts the parallel scancode from the 3278 keyboard to a serial PS/2 scancode.

See: http://www.ibmsystem3.nl/IBM3278 (http://www.ibmsystem3.nl/IBM3278)

Henk

(http://ibmsystem3.nl/IBM3278/Doc&Pics/PCB.jpg)

Title: Re: IBM 3278 to PS/2 interface
Post by: snhstq on Sat, 16 November 2013, 00:56:21

Forgot to add a picture of a 3278 keyboard.

(http://az413224.vo.msecnd.net/img/7741/m_s_p_7741_1.jpg)

Title: Re: IBM 3278 to PS/2 interface
Post by: fohat.digs on Sat, 16 November 2013, 09:50:08

Great work!

I presume that it is programmable. Now I just have to find one of those dinosaurs.

Title: Re: IBM 3278 to PS/2 interface
Post by: Halvar on Mon, 18 November 2013, 00:55:42

Thanks for posting here!

We had a short discussion about your converter on Deskthority (http://deskthority.net/keyboards-f2/ibm-3278-beamspring-to-ps-2-controller-t6828.html) just yesterday.

Yours looks like a very cool  solution with the advantange that it can be used fully extern, without even opening the historic keyboard. And I would probably even be able to build it, because there's no SMD soldering involved.

I'd also like to know more about how programming the controller works. I think the ATMega has an EEPROM -- do you take the chip out and put it in a programmer if you want to change something?

How did you cope with only three keys that send break signals? I'm not sure if I understand how you programmed the modifiers. Do you use one of the shift keys as Control? Or did you define shortcuts in the adapter for just some common Linux CTRL combinatons and have no way to use others?

I just bought an 3278 two weeks ago, and have one of xwhatsit's controllers (http://deskthority.net/workshop-f7/beamspring-usb-controller-t6044.html) on its way to me. His approach is different (and more intrusive), he completely replaces the controller and uses an ATmega32u2 to convert to USB. He also posted in the thread that I mentioned. Very exited to get my hands on one.