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C=Key Keyboard Adapter

  • C=Key (PS/2 KB to VIC/64 Configuration Shown)
2.40 Ounces
Calculated at checkout

Product Description

C=Key bridges the gap between Commodore and PC keyboard operation!

Depending on configuration, C=Key offers VIC-20, C64, C64C, SX64, C128, C128D, and C128DCR owners the ability to either use their CBM keyboard with a PS/2 supported PC, or utilize a PS/2 keyboard on their Commodore machine.  In either usage, multiple keyboard mappings are supported, to handle keyboard differences and application preferences.  No drivers or programming are required for operation.

C=Key can be purchased in the following configurations:

  • PCB Only: Bare circuit board
  • PCB + uC: PCB and programmed Atmel ATMEGA162, used for connecting CBM KB to PC (includes uC Crystal and trimming capacitors)
  • PCB + uC + Crosspoint Switch: Allows either configuration
  • Preconfigured kits for specific CBM models.
  • Full Kit: Adds resistors, diodes, and jumper blocks for correct operation and connectors for any configuration

Additional options include:

  • dual joystick connectors can be added, to allow CBM joystick operation on the PC.
  • Any kit can be ordered pre-assembled (please allow additional handling time)


  • A PS/2 compatible keyboard (USB keyboards with PS/2 converters may not work) with a Mini-DIN6 plug.
  • One of the following machines:
    • VIC-20, C64, C64C
    • SX64
    • C128
    • C128D/C128DCR
  • For the C128D/C128DCR operation with a PC Keyboard, a DB25M to DB25M cable is also required.

Technical Details

C=Key consists of an Atmel ATMEGA162 microcontroller in DIP format and an optional Mitel/Zarlink MT8812 crosspoint switch.  In "host" mode, the system reads data from the PS/2 keyboard and emulates the Commodore switch matrix with the crosspoint switch.  In "device" mode, the system scans the Commodore keyboard matrix 60 times a second, converting keypresses into PS/2 compliant scan codes.  GPLv2 licensed C firmware source code can be modified to support nearly any matrix-style keyboard configuration.

Firmware features include:

  • Multiple key rollover support
  • Configurable keyboard matrix scanner supports 1x1 to 16x8 matrices (hardware supports a maximum of 12x8 matrices)
  • Single IC solution (for matrix keyboard to PC configuration)
  • Key repeat functionality supported and PS/2 keyboard compliant

The PCB features include:

  • A single PCB for VIC/64/128/SX64
  • Support for dual joysticks for emulator use.
  • Through hole design makes "do-it-yourself" construction easy.


We've hesitated to offer these kits in the store because the firmware has not been extensively tested and cannot be easily upgraded by the end user.  In fact, we are planning to redesign this unit to utilize USB technology, which would allow easier upgrades and support for more current technology.  However, due to overwhelming demand, we're offering the kits and assembled units.  Nonetheless, we consider this a project, not a product and do not intend to offer complete support for the unit.  If you are looking for a complete product offering with full support, please wait for our USB development effort to complete.  If you purchase this unit, we highly encourage your to obtain an Atmel AVR USB Programmer.

Note: Assembled units are hand manufactured after orders are placed, and typically ship 4 weeks after order placement.

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