Documentation for “Zerocat PS/2-Keyboard”
Generated on: Sat, 18 Jun 2022 13:33:21 +0200
Copyright (C) 2017, 2018, 2020, 2021, 2022 Kai Mertens email@example.com
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
Within this project’s git repository, versions are tagged according to the following pattern:
<major>– The resulting product is a major change or upgrade.
<minor>– Additional functionality or new features are introduced.
<revision>– Bug fixes, minor changes, graphical stuff.
The goal of Zerocat PS/2-Keyboard is to provide you with a save keyboard, driven by a free-design microcontroller board.
All paths within this document are relative in respect to the original
location of this source file, which is located in the project’s
It is assumed that you are running a GNU/Linux-libre operating system.
Use git to clone the project’s sources:
git clone git://zerocat.org/zerocat/projects/ps2-keyboard
Change into the project’s documentation folder:
README.md to get started:
If you are on GNU Guix System, use make to create a dedicated profile, once. This allows you to match your environment to the one used by Zerocat, thus producing bit-identical results:
make -C ../guix pull
Create an empty environment with dedicated guix channel:
make -C ../guix environment
Create a shell with all prerequisites set up:
make -C ../guix shell
To leave the shell and the environment, later on, when you are done with this project, type:
To remove this project’s handy guix profile, type:
make -C ../guix clean
This will remove symlinks only. If you want to remove the profile from your system, run the GNU Guix Garbage Collector.
To list all available targets, type:
make -C ../guix help
If you are on another distro, check file ../guix/manifest.scm and install the listed packages with your package manager, manually. Adapt package names as required.
To build the documentation, type:
make -C ../doc
To get a full list of available targets, type:
make -C ../doc help
To clean-up, type:
make -C ../doc clean
To build the firmware, type:
make -C ../firmware/src
To get a full list of available targets, type:
make -C ../firmware/src help
To clean-up, type:
make -C ../firmware/src clean
Zerocat PS/2-Keyboard ships copyrighted work.
Zerocat PS/2-Keyboard is free software. It makes use of free software approved licenses only and should be freely distributable:
Authorship, copyright and license information may be provided in more detail on a per-folder and/or per-file basis. Check the sources.
Please report a bug if you find the distribution hindered.
See Zerocat Website for contact information.
Documentation source files are written in markdown syntax. They should carry their individual copyright and license notices right below the title giving headline, e.g.:
<Title-of-Document> =================== Copyright (C) <Year> <Name-of-Author> <Email-Address> Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". <Other-Headline> ---------------- ...content...
The generated documentation carries a license notice right at top on
its title page, with copyright statements generated from
Sections of the generated documentation are build from selected markdown source files, with their individual copyright and license notice stripped.
In order to enrich the generated documentation ...
*.mdmarkdown source files to
... and adapt ../doc/Makefile to produce nice output.
In case more tools are needed, don't forget to update ../guix/manifest.scm.
To make your image look nice within the documentation, select a landscape layout of 16:9 aspect ratio.
Use ImageMagick to prepare your image, e.g.:
If your image is big, reduce it to a maximal width of 2000 pixel:
mogrify -resize 2000x <image>
Please clean image files from metadata, before committing, i.e.:
mogrify -strip <image>
If you embed your image into a markdown documentation file, use this syntax:
![<path/to/image>] [<path/to/image>]: <path/to/image> "title message"
![<path/to/image>][my-image-shortcut] [my-image-shortcut]: <path/to/image> "title message"
These patterns will guarantee that
<img> tags will have their
title attributes properly set within the html output.
Please use this license header for code source files:
Zerocat PS/2-Keyboard --- Get rid of keyloggers. Copyright (C) <Year> <Name-of-Author> <Email-Address> This file is part of Zerocat PS/2-Keyboard. Zerocat PS/2-Keyboard is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. Zerocat PS/2-Keyboard is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Zerocat PS/2-Keyboard. If not, see <http://www.gnu.org/licenses/>.
If you intend to write shell scripts, use this skeleton to make them work for GNU Guix:
#!/bin/sh # Re-exec if we are not using Bash or are using Bash in POSIX mode. if [ -z "$BASH" ] || [ "$BASH" = "/bin/sh" ]; then bash=`command -v bash` if [ -z "$bash" ]; then echo "Couldn't find Bash, sorry!" exit 1 else exec "$bash" "$0" "$@" fi fi # We're using Bash now. set -o errexit set -o nounset set -o pipefail # Your code goes here ...
Update ../doc/NEWS.md and list your contributions.
You can use
git shortlog to get a starting point for your edit.
Looking for articles by author Adam Chapweske
PS/2 is now considered a legacy port, which continues to be included on many computer motherboards.
PS/2 ports may be favored for security reasons [...] as they allow USB ports to be totally disabled, preventing the connection of [...] malicious USB devices
The PS/2 interface provides no restriction on key rollover.
The PS/2 interface has near-universal compatibility with BIOS.
They cause fewer problems when KVM switching with non-Wintel systems.
The PC 97 standard introduced a color code: the keyboard port, and the plugs on compliant keyboards, were purple; mouse ports and plugs were green.
The pinouts of the connectors (keyboard vs. mouse) are the same, but most computers will not recognize devices connected to the wrong port.
PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable.
Standard PS/2 mice send interrupts at a default rate of 100 hertz when they have data to send to the computer.
PS/2 allows the sample rate to be overridden, with PS/2 supporting a sampling rate of up to 200 Hertz.
Function | 6-pin DIN (PS/2) | 5-pin DIN (AT/XT) | 6-pin SDL -------- | ---------------- | ----------------- | --------- +5V | 4 | 5 | E DATA | 1 | 2 | B not connected | 2, 6 | 3 | A, F GND | 3 | 4 | C CLK | 5 | 1 | D
> > Socket: Plug: > 6 _ 5 5 _ 6 > o | | o · | | · > |_| |_| > o o · · > 4 3 3 4 > o o · · > 2 1 1 2 >
> > Socket: Plug: > _ _ _ _ > \_/ \_/ > > 3 1 1 3 > o o · · > 5 4 4 5 > o 2 o · 2 · > o · >
> > Socket: Plug: > > > xxxxxxxxxxxxxxx xxxxxxxxxxxxxxx > | | | | | | | | | | | | > F E D B C A A B C D E F > >
Mainboards and ThinkPad docking stations often carry a so called PS/2 Combi Port, with keyboard and mouse icons at the outlet. The exact wiring is unknown to the author, three options should be taken into account. Each option would require different usage of a dedicated Y-Splitter-Cable.
Combi Port is a PS/2-Keyboard Port with extra clock and data lines for mouse at pins 6 and 2.
Combi Port is a PS/2-Mouse Port with extra clock and data lines for keyboard at pins 6 and 2.
Combi Port is a standard PS/2 port (pins 6 and 2 not connected) which is able to detect the type of device at boot time. Using both devices (keyboard and mouse) simultaneously is not supported.
Port types 1.) and 2.) would require to use a Y-Splitter-Cable (see Figure A) for simultaneous operation of keyboard and mouse. Port type 2.) would additionally require to twist the plugs, thus using the mouse with the keyboard plug and vice-versa.
> > Figure A: PS/2 Y-Splitter-Cable > =============================== > > 6-pin Mini-DIN 6-pin Mini-DIN 6-pin Mini-DIN > (PS/2 Combi Port) (PS/2-Keyboard) (PS/2-Mouse) > > 1 -------------------------- 1 > 2 --------------------------------------------------------1 > 3 -------------------------- 3 -------------------------- 3 > 4 -------------------------- 4 -------------------------- 4 > 5 -------------------------- 5 > 6 --------------------------------------------------------5 > >
Note the different layout of a Y-Splitter-Cable which allows for simultaneous usage of keyboard-like devices:
> > Figure B: PS/2 Y-Splitter-Cable > =============================== > > 6-pin Mini-DIN 6-pin Mini-DIN 6-pin Mini-DIN > (PS/2 Keyboard Port) (PS/2 Keyboard) (PS/2 Barcode Scanner) > > 1 -------------------------- 1 -------------------------- 1 > 3 -------------------------- 3 -------------------------- 3 > 4 -------------------------- 4 -------------------------- 4 > 5 -------------------------- 5 -------------------------- 5 > >
Coreboot seems to not support PS/2 hardware in first place. Documentation about PS/2 is often lacking details on coreboot’s board status pages. i.e.:
Exact lists about which hardware works how has to be gathered individually and would be a required source of information.
What about ground connection? Ground Loop?
+-----------------------+ +----------------------+ | | | | | ASRock E350M1 |<-- USB Power -->| Zerocat | | Coreboot Machine |<---- PS/2 ----->| PS/2 Controller | | with PS/2 Port, | | Board | | no Keyboard attached | | | | | +----------------------+ +-----------------------+ ^ ^ | | | | RS232 | | | | | v +-----------+ +----------------------+ | | | | | 230VAC |------------------->| Laptop ZC-X60 | | Power | | + Docking | | | | + RS232 Port | +-----------+ | | | uploads firmware, | | issues key-strokes | | | +----------------------+
+-----------------------+ | | +----------------------+ | Laptop ZC-T60 | | | | + Docking |<-- USB Power -->| Zerocat | | + RS232 Port? |<---- RS232 ---->| PS/2 Controller | | + PS/2 Port |<---- PS/2 ----->| Board | | | | | | | +----------------------+ +-----------------------+ ^ | | +-----------+ | | | 230VAC | | Power | | | +-----------+
Nothing evolved, so far. Let’s start with this basic board:
Board Schematic PNG Preview
Article about USB Security Flaw
General info about PS/2
The PS/2 Keyboard Interface
The PS/2 Mouse/Keyboard Protocol
Keyboard Scan Codes -- Set 1
Keyboard Scan Codes -- Set 2
Keyboard Scan Codes -- Set 3
good short description
Keyboard scancodes in detail
See photo in section “Keyboards And Webcams And Hard Drives”.
Informative resource on keyboards and pointing devices
ThinkPad X200 Keyboard Disassembled (Mechanics of one Key Missing)
Original Layout: DE
Seems to have 8 rows and 15 columns of keys:
However, the corresponding X200 sysboard schematics depicts a matrix of 8 rows and 16 columns.
No internal keyboard controller in use.
Foil connector pads in total: 40 (see photo)
Double layer connector cable, schematic needed!
simple flat connector pads to keyboard: 40
splits towards... (see photo)
Sysboard Plug “JAE CONN40A-1-U1GP”
Similar, but wrong JAE Connectors:
and trackpoint board (6x signal, 2x power)
note cable is covered with self-adhesive thick aluminium foil when mounted
integrated trackpoint hardware
soldered towards flat-cable with eight pads
Trackpoint controller is PTPM754DR 32-pin SSOP, no datasheet available. To get some ideas, please refer to:
additional chip (Quad OpAmp):
Keyboard Cable, splits towards Systemboard and Trackpoint
Systemboard Connector, unknown Type
Schematic of an X200 Keyboard Cable with 32-pin PTPM754DR TrackPoint Controller
As visible from the x200 keyboard cable schematics, the keyboard foil pads are organized in...
...resulting in 36 active pads.
Double Layer with integrated Vias
Keyboard Connector Pads, Top and Bottom
Please read PS/2 to get prepared for PS/2 basics.
The trackpoint board is connected to the keyboard cable by eight soldered pads, referenced by names Pad-1..Pad-8 within this documentation. Pad-1 is located close to the board’s edge.
Pad Number | Function | Remarks | 9-pin Sub-D Test Plug ---------- | -------- | ------- | --------------------- 1 | CLK | close to board’s edge | 9 2 | RST | can be connected to positive POR, alternatively | 4 3 | MIDDLE BUTTON | - | 8 4 | RIGHT BUTTON | - | 3 5 | LEFT BUTTON | - | 7 6 | DATA | - | 2 7 | VSS (GND) | connected to thicker route in keyboard cable | 6 8 | VCC (+5V) | connected to thicker, edgemost route of keyboard cable | 1 - | - | - | 5
> > Alternative POR at RST (Pad 2) > ============================== > > C > VCC --------||------+ > 2.2µF | > | R > RST ----------------+------/\/\/------- GND > 100K >
The Keyboard Cable has been modified to ease experimenting with the disassembled Trackpoint Board. Test Connector is a SUB-D9 male plug.
Modified Keyboard Cable to Ease Experimenting
Controller in use is the TPM754 from Philips Semiconductors. This is a 8051-based machine which runs proprietary code from IBM:
“IBM has licensed Philips Semiconductors to sell microcontrollers with TrackPoint code. By purchasing a TPM from Philips, the purchaser becomes a sub-licensee of Philips. The selling price of Philips’ TPM includes the royalties for IBM’s intellectual property, which Philips in turn pays to IBM. Customers for TPMs do not need to sign any licensing agreement with either IBM or Philips. This code is the intellectual property of IBM, which is covered by numerous patents, and must be treated accordingly.” --- Philips Semiconductors TPM754 Datasheet
The TPM754 comes in different packages with different ordering codes. Unfortunately there is no datasheet nor pinout available for the 32-pin SSOP package (ordering code PTPM754DR), but in regard to measurements and the 28-pin SSOP datasheet, the pinout can be guessed in a straight foreward approach.
Pin | Function | Connected Board Pad | External PS/2 Mouse (6-pin Mini-DIN) --- | -------- | ------------------- | ------------------------------------ 1 | RxD/T0/P3.4 | - | Pin 1 (DATA) 2 | TxD/T1/P3.5 | Pad 1 (CLK), close to edge | - 3 | ECI/P3.6 | - | - 4 | INT1/P3.7 | - | Pin 5 (CLK) 5 | RST | Pad 2 (RST) | - 6 | X2 | - | - 7 | X1 | - | - 8 | VSS | Pad 7 (GND) | Pin 3 (GND) 9 | ZIN | - | - 10 | YIN | - | - 11 | XIN | - | - 12 | XYZRAMP | - | - 13 | AVSS | - | - 14 | AVCC | - | - 15 | not connected | - | - 16 | not connected | - | - 17 | VCC? AVCC? | - | - 18 | not connected | - | - 19 | DECOUPLE | - | - 20 | VREG | - | - 21 | XYDACBIAS | - | - 22 | XYSOURCE | - | - 23 | ZDAC/ASEL | - | - 24 | XYDAC | - | - 25 | P1.2 | - | - 26 | VCC | Pad 8 (VCC) | Pin 4 (VCC) 27 | CEX/P1.1 | - | - 28 | INT0/P1.0 | Pad 6 (DATA) | - 29 | P3.0 | Pad 5 (LEFT BUTTON) | - 30 | P3.1 | Pad 4 (RIGHT BUTTON) | - 31 | P3.2 | Pad 3 (MIDDLE BUTTON) | - 32 | P3.3 | - | -
Warning: If the TrackPoint is replaced by a PS/2-Mouse, interfacing with the sysboard’s H8 controller doesn't work. Probably, H8 and TrackPoint Controller do not talk according to PS/2 standards??
Although no interface is provided to attach an additional external PS/2 Mouse, pins 1 and 4 of the TPM754 can be used as a workaround in conjunction with the VCC and GND power lines. The IBM code separates data streams from Trackpoint and Mouse clearly, so that one device moves the screen pointer without being irritated by the other.
Experimental Setup with External PS/2 Mouse
Connecting the Trackpoint Board
> > Connect Trackpoint via Test Plug to a Standard PS/2 Mouse Port > ============================================================== > > > +---------VCC---------------------+--------> to Pin 4 > | +----------------DATA-----------|--------> to Pin 1 > | | | > | | +------RST-------+---||-----+ > | | | | 2.2uF > 1|2|3 4|5 | > \ · · · · · / +--/\/\/---+ > \ · · · · / 100K | > 6|7 8 9| | > | | | > | +-----------CLOCK----------|--------> to Pin 5 > +---------GND--------------------+--------> to Pin 3 > > Sub-D9 Test Plug ----> PS/2 6-pin Mini-DIN > >
This setup has been proved to work with a D945GCLF Intel Desktop Board, running blobless coreboot firmware and the Trisquel7 Operating System. The Trackpoint and its attached external PS/2-Mouse is recognized at the PS/2 Mouse Port along with a PS/2-Keyboard (IBM Model M) attached to the PS/2 Keyboard Port. The reset line of the Trackpoint is simulated by the alternative Power-On-Reset circuit.
Trackpoint with External PS/2-Mouse at Standard PS/2 Mouse Port of a Blobless Coreboot Machine
> > PS/2-Keyboard Setup using an X200 Keyboard Matrix with Trackpoint and external Mouse > ==================================================================================== > > > ···························································································· > : : > : +-----------------------------------+ : > : +-----------------------+ | Board with Free-Design Controller | : > : | X200 Keyboard |-----GND---/4----------| ================================= | : > : | ============= | | | : > : | |=====PB and Hotkey=========discard or translate====+ | : > : | No controller in use. | |___ | | : > : | |-----KBDID0----------->| | | | : > : | * Power Button (PB) |-----KBDID1----------->| ? | | | : > : | * Fn Hotkey |-----KBDID2----------->|___| | | : > : | * Matrix 16x8 | | | | : > : | * 3 Mouse Buttons |-----Matrix 16x8-----------------/24----------+ | | : > : | * KBDID0..2 Lines | | | | | : > : | * 4x Ground |---Mouse Button M----->| | /2 | : > : | = 36 Pads |---Mouse Button R----->| | | | : > : | |---Mouse Button L----->| | | | : > : +-----------------------+ | v v | : > : | +················+ | : > : | : translate into : | : > : +-----------------------+ | : PS/2 : | : > : | TrackPoint Board |<<====+5V, GND===============\\ +················+ | : > : | ================ | | || ^ | : > : | |<---Mouse Button M-----| __||___________ | | : > : | 8051-based controller |<---Mouse Button R-----| | +5V, GND | | | : > : | (PTPM754DR) runs |<---Mouse Button L-----| |_______________| | | : > : | proprietary code | | | ^ ^ | | : > : | from IBM. |<-------Reset----------| | | | | | : > : | | | /2 /2 /2 /2 | : > : | * 3x Mouse Buttons | PS/2-Trackpoint | | | | | | : > : | * PS/2 (clock, data) |<=======clock/data================+ | | | : > : | * Reset Line | PS/2-Mouse | | | | | | : > : | * Ground | | | | +-----| | : > : | * +5V Power | Ext. PS/2 Mouse | v | | | : > : | * Ext. PS/2 |<======clock/data===========+ | | | : > : | = 10 Lines | | | | | | : > : | | | | | | | : > : +-----------------------+ +----|-----|-----------|------------+ : > : | | | : > : PS/2-Keyboard with Trackpoint /4 /4 /4 : > ························································|·····|···········|················· > | | | > +--------Ext. PS/2-Mouse-----------------+ | | > | | | > | v v > | +-----------------------------------------------------+ > v | :| PS/2 | | PS/2 |: | > +------------------------+ | :| Mouse | | Keyboard |: | > | External PS/2 Mouse | | :|_______| |__________|: | > | =================== | | ·····PS/2-Combi-Port?····· | > | | | | > | proprietary controller | | Blobfree Coreboot Computer or Laptop | > | | | ==================================== | > | * PS/2 | | | > | = 4 Lines | | * with two PS/2 Ports | > | | | * or with one PS/2 Combi Port and Y-Splitter-Cable | > +------------------------+ | | > | Working Example(s): | > | | > | * D945GCLF Desktop Board with Blobless Coreboot | > | |
In case a desktop board with blobless coreboot is used as host, this PS/2 free-design keyboard would significantly improve the computer user’s situation in respect to freedom and security. Let’s go for prototyping!
Version 1.3, 3 November 2008
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