Keyboard controller chip

Discussion in 'The Projects Forum' started by Scott_M, Feb 5, 2010.

  1. Scott_M

    Thread Starter Active Member

    May 8, 2008
    Hi Guys

    I havn't been around in awhile .... seems I only show up when I need help :( sorry.

    I am looking for a preprogrammed USB Keyboard chip. Or a suggestion for a chip that will fill my needs.
    I do have access to an eprom programmer but have no programming skills.

    Here is what I need the chip to output.

    "alt + r "
    "alt + s "

    That's it.
    It needs to be a USB interface and recognized by windows as a HID compliant device

    I built my prototype by hacking an old keyboard, it works great. I need to build some more and need some alternatives.

    Here is a picture of the prototype.


    The yellow button has one pair of wires and one switch, it is sending the “space” command.
    The green and red buttons are the “alt + r" and "alt+ s “ commands. I filled a little bit off of the “r + s “ switch lobes so the “alt” command comes first.
    All switches are N.O. momentary contacts.

    When plugged in it is recognized as a Compaq keyboard and is listed as a HID compatible device.

    I have looked at devices like the ipac keyboard emulators but they are pretty pricey.

    Any help would be greatly appreciated
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
    You can use a microcontroller that has USB interface. An example would be Microchip PIC18F2550, or the cheaper PIC18F13K50. There is a free example firmware available implementing a HID USB keyboard, it is included in the Microchip USB Framework package. You can modify this example firmware to scan the pins connected to the buttons and send the appropriate scancode. This is the most economical soution, IMO.

    The drawbacks are you need to modify the firmware program to your particular application, and need a programmer to burn the firmware to the micro. If you are not up to the task of modifying the firmware, maybe you could find someone who could.
  3. Scott_M

    Thread Starter Active Member

    May 8, 2008
    Thank you !

    From my initial look that looks like it will work nicely.

    Now I need to find someone to help with the programming.