Back in 2008, I picked up a few IBM 6094-020 Lighted Program Function Keyboards from someone on the classiccmp mailing list. These are an array of keys and lights which were used as a user interface for some kind of CAD product on the RS/6000 AIX platform.
Codeninja had already reverse-engineered the protocol – but it seems their LPFK used a non-standard protocol.
Michael Brutman later obtained a copy of the LPFK Model 6094-020 commands (used on the standard LPFK) and published these online. liblpfk implements this version of the LPFK protocol.
The API is pretty simple:
Several demos are included in the liblpfk source code:
Doxygen comments are present in the code, which means documentation may be generated simply by running doxygen over it.
Mercurial repository: http://hg.philpem.me.uk/liblpfk/
The LPFK uses RS232 communications, and requires around 500mA of current with all the LEDs on.
I used an FTDI TTL232 cable and a MAX232 to drive the LPFK, with power taken directly from the PC's USB port.
I also reprogrammed the FT232's EEPROM so that it declared its need for 500mA of power to the host PC (this is done with FTDI's FT-PROG tool).
The mini-DIN pinout is as follows:
| Pin | Function |
|---|---|
| 1 | GND (signal return) |
| 2 | GND (DC return) |
| 3 | +5V |
| 4 | Reset (leave floating, +5V/GND levels) |
| 5 | TxD (connect to PC RxD) |
| 6 | RxD (connect to PC TxD) |
| 7 | No connect |
| 8 | No connect |
This is the same as the pinout for the IBM Graphics Input Adapter MCA card, FRU 22F9758.
Pinouts and diagrams are in IBM document SA38-0533-04, "Adapters, Devices, and Cable Information for Micro Channel Bus Systems" on page 1-134 (PDF page 154).
Daniel Drucker has written a Python library to control the LPFK.