[REQUEST FOR TEST] TMK IBM PC Keyboard Converter

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05 Dec 2019, 01:11

IBM PC Keyboard Converter

The converter translates IBM PC keyboard protocols to plug classic keyboards into modern computer with USB ports. It supports both IBM XT and AT protocols, and all of scan code set 1, 2 and 3 with one firmware.

This project is intended to integrated existent TMK XT, PS/2 and Terminal converters.
- IBM XT converter: https://geekhack.org/index.php?topic=94649.0
- PS/2 converter: https://geekhack.org/index.php?topic=14618.0
- IBM Terminal converter: http://geekhack.org/index.php?topic=27272.0

This is not finished project yet and still work in progress as of 2019-12-02. Test in the field and feedback from users are needed to improve.

Try prebuilt firmware below and report your result, please.
Post your keyboard model number here, also debug outputs on hid_listen would be helpful.

The converter need to be tested with keyboards below particularly, as of 2020-03-02.

- IBM PC XT 83-key
- IBM PC AT 84-key

Keyboards tested
Looking forward to your report!

- IBM 122-key Terminal: 6110345, 6111070, 6110344

- IBM XT 83-key: 4584656

- AT Keyboards: DS-2001

Keyboards that should be tested

- PC XT keyboard of IBM 5150 5160
- - 83-key: 1501100 1501105
- PC AT keyboard of IBM 5170
- - 84-key: 6450200 6450225
- PC Terminal keyboard of IBM 5271(3270 PC)
- - 122-key: 6110344 6110345 1397000
- - 102-key: 1390680 1395764 1392595
- PS/2 keyboards
- Clones of above models


Firmware supports ATMega32u4 by default, Teensy2/2++ or ProMicro can be used.
Wire controller pins below to keyboard signals, besides VCC and GND. This is compatible for Soarer's converter.

- Data: PD0
- Clock: PD1
- Reset: PB6 or PB7 (For some of XT keyboards. Not needed for AT, PS/2 and Terminal)

Pull up resistors of 1-4.7K Ohm on both Data and Clock line are recommended, without them it won't work in some cases.

Old Type-1 IBM XT keyboard and some of XT clones need this to reset its controller on startup. Many of IBM XT keyboards available are Type-2 and don't need the reset pin.

See this for Type-1 vs Type-2:
https://vintagecomputer.ca/ibm-pc-model ... vs-type-2/

As for clones Zenith Z-150 XT and Leading Edge DC-2014 are known to need this.

Connector pinouts
- http://www.kbdbabel.org/conn/kbd_connector_ibmpc.png
- https://allpinouts.org/pinouts/connecto ... -xt-5-pin/

- http://www.kbdbabel.org/conn/kbd_connector_ps2.png
- https://old.pinouts.ru/InputCables/Keyb ... nout.shtml

- https://pinouts.ru/InputCables/KeyboardPC6_pinout.shtml

- http://www.kbdbabel.org/conn/kbd_connector_ibmterm.png
- http://www.kbdbabel.org/conn/kbd_connec ... x_319x.png

Source Code

https://github.com/tmk/tmk_keyboard/tre ... /ibmpc_usb

Prebuilt Firmware

https://github.com/tmk/tmk_keyboard/tre ... usb/binary

Build Firmware

$ cd converter/ibmpc_usb
$ make clean
$ make

Keyboard discrimination

This section explains how the converter determines proper protocol and scan code set for keyboard. The converter need to do that before starting to receive and translate scan codes from keyboard.

Keyboard ID
After startup the converter sends 0xF2 command to get keyboard ID and sees how the keyboard responds to the command.

Response from keyboard:

- XT keyboard doesn't support any command and returns no response.
- AT keyboard should respond with 0xFA to the command but returns no keyboard ID.
- PS/2 keyboard should respond with 0xFA to the command, followd by keyboard ID, such as 0xAB86.
- Terminal keyboard should respond with 0xFA to the command, followed by keyboard ID, such as 0xBFBF.

Now we can dscriminate the keyboard and determine suitable protocol and scan code set as described below.

- Signals from XT keyboard are recognized by XT protocol.
- Signals from AT, PS/2 and Terminal keyboard are recognized by AT protocol.

Scan code Set
- Scan codes from XT keyboard are handled as CodeSet1.
- Scan codes from AT and PS/2 keyboard are handled as CodeSet2.
- Scan codes from Terminal keyhboard are handled as CodeSet3.


Use hid_listen to see debug outputs from the converter.


Code: Select all

Waiting for new device:...


USB configured.

Keyboard start.
rAA rBF rBF wF5 rFA wF2 rFA rBF rBF wF4 rFA ID: BFBF
kbd: Terminal
wF8 rFA  


IBM PC Keyboard Protocol Resources:

a. Microsoft USB HID to PS/2 Translation Table - Scan Code Set 1 and 2
http://download.microsoft.com/download/ ... nslate.pdf

b. Microsoft Keyboard Scan Code Specification - Special rules of Scan Code Set 1 and 2
http://download.microsoft.com/download/ ... ancode.doc

1. PS/2 Reference Manuals - Collection of IBM Personal System/2 documents

2. Keyboard and Auxiliary Device Controller - Signal Timing and Format

3. Keyboards(101- and 102-key) - Keyboard Layout, Scan Code Set, POR, and Commands

4. IBM PC XT Keyboard Protocol
https://github.com/tmk/tmk_keyboard/wik ... d-Protocol

5. IBM Keyboard Scan Code by John Elliott - 83-key, 84-key, 102-key and 122-key

6. IBM 1391406 Keyboard - Scan Code Set 2 of 102-key PS/2 keyboard

7. The IBM 6110344 Keyboard - Scan Code Set 3 of 122-key terminal keyboard

y. TrackPoint Engineering Specifications for version 3E
https://web.archive.org/web/20100526161 ... nload.html

z. Soarer's XT/AT/PS2/Terminal to USB converter


* Reset method for rescue
For converter without accesible reset button when magickey combo doesn't work.
Check pin status at powerup:
- if Data and/or Clock are pull down to GND

* Force protocol and scan code set
Keyboard discrimination may fail and you have to configure them by hand.

Last edited by hasu on 14 Mar 2020, 01:48, edited 7 times in total.

User avatar

05 Dec 2019, 01:22

This is exciting! I will begin to convert my soarer's converters to this for my F122 and other boards. Just have to break open the orihalcon cable and jerryrig reset pins directly to the 32u4.

User avatar

05 Dec 2019, 01:54

Looks promising: TMK has learned all of Soarer’s multi-protocol handling tricks!

I hope this will be Unimap compatible when you’re done! I love defining everything graphically.

User avatar

05 Dec 2019, 02:02

Okay. I'm in for this.

User avatar

05 Dec 2019, 02:21

ZedTheMan ,
Yes, reset button would be a must-have when in trouble.
I don't recommend to use converter without reset button like orihalcon's for now at least. To use Teensy or Pro Micro is fine and safe.

If the firmware recognize your keyboard correctly you can put it into bootloader mode by holding 'Left shift + Right shift + Pause'. But if not you won't be able to acccess bootloader without reset button. I have a plan to add emergency rescue method for the situation.

I'll add specific support for this converter to my Keymap Editor some later.
But until then, you can do with trick below.

0. Download prebuilt firmware
1. Open Editor: http://www.tmk-kbd.com/tmk_keyboard/edi ... p/?usb_usb
2. Select the downloaded file on file chooser in 'Base Firmware File:' section
3. Click 'Load keymap from firmware' button
4. Edit your keymap
3. Then, click 'Download' button

John Doe

05 Dec 2019, 02:23

Nice job, ill have a try on my at/122 to see what will happen. Appreciate it.

User avatar

06 Jan 2020, 03:09

anyone can help?

REQUEST FOR HELP: Try and report your result.
Post your keyboard model number here, also debug outputs on hid_listen would be helpful.

User avatar

04 Mar 2020, 04:14


User avatar
Gotta start somewhere

04 Mar 2020, 04:56

Would it be possible to test a Wyse? I can test some AT boards soon.

User avatar

04 Mar 2020, 05:53

Hi Hasu, sorry for not responding. I will flash this to my xt usb converter and try it with various boards I have when I have time, but this may take a bit, sorry.

User avatar
Gotta start somewhere

04 Mar 2020, 06:39

Works like a dream on my DS-2001! Thanks Hasu!

Soarer's kept messing up every time I stopped using it for awhile. DS-2001 uses AT protocol fyi.
IMG_9700.JPG (281.43 KiB) Viewed 294 times

User avatar

04 Mar 2020, 10:53

Redmaus, Thanks for the test!
and good to know it works with the keyobard.
As for Wyse, this doesn't support Wyse proprietary protocol. If the board speaks in AT, XT or Terminal protocol the converter should works.

At this time I'm interested in test results with keyboards below particularly.
It would be helpful to debug firmware if someone with the boards can test the converter with them.

- IBM PC XT 83-key(Model F)
- IBM PC AT 84-key(Model F)

User avatar

13 Mar 2020, 21:32

I can't promise I'll do it yet (not sure if I have parts on hand) but I own both of those keyboards so I'm going to "half" commit to testing the two Model Fs for you today or tomorrow.

Stuff like this is the least we can do after you've contributed so many great projects to the keyboard world, Hasu :)

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