Custom bluetooth keyboard

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Revision as of 13:15, 23 September 2011 by Ron (talk | contribs)
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Bluetooth conversion of a Kinesis contour keyboard to a bluetooth keyboard.

Brainstorming

Available approaches

Options Pros Cons
USB HID to bluetooth adapter
  • No modification of the keyboard necessary (for USB versions of the keyboard)
  • Usable on any USB keyboard
  • USB HID host chips are uncommon and expensive
  • Programming USB HID host may be complicated
  • PS/2 version of keyboard may or may not have USB output (though there are USB related markings on the PCB)
    • If capable, would likely require modifications to the original controller board
PS/2 to bluetooth adapter
  • Simpler to decode than USB HID
  • Any microcontroller can be used
  • No modification of the keyboard necessary (for PS/2 versions of the keyboard)
  • Usable on any PS/2 keyboard
  • USB version of keyboard may or may not have PS/2 output
    • If capable, would likely require modifications to the original controller board
Custom replacement keyboard controller with integrated bluetooth
  • Getting data directly from button matrix is likely simpler than decoding some other protocol
  • Opportunity to add extra features
  • Likely better battery life
  • Any microcontroller (with enough IO) can be used
  • Supposedly replacement key wells can be had for < $90 directly from Kinesis. Add on some extra keycaps and the thumb boards and the custom controller and you could have a brand new, bluetooth Kinesis for much less than a brand new one.
    • A case would need to be made, but many people have modded their existing cases so the two halves are physically separated anyway, plus I personally think that the the thumb buttons could be at a slightly better angle, so that could be considered another pro (good use for AsentWorks 3D printer)
  • Kinesis keyboards have some advanced programmability - reimplementing that on a custom controller could take some time
  • Requires interfacing with the key matrix directly which either requires special connectors or soldering to the key matrix

Features

  • Bluetooth module might have audio capabilities in addition to the required HID function
    • Use keyboard as audio extender - include a headphone port in keyboard
    • Kinesis has a key recognition click speaker built in which can be hard to hear when listening to music, but might still annoy others
      • Overlay key click sound over bluetooth audio signal
  • USB interface for charging
    • disable bluetooth while charging and instead use the USB connection
  • Saving, editing, and uploading custom keyboard layouts to the keyboard from the computer
    • Cross platform application
    • Keyboard layers could be saved, exported, and uploaded individually
      • Example:
        • Standard keyboards have "qwerty" on the base layer and the shift key brings them to the next layer containing "QWERTY" (assuming qwerty keyboard)
        • The Kinesis firmware has a keypad layer, so when you press the keypad button, the keys under the right hand become a numpad and the shift key moves between the layers of the numpad (numbers or arrows)
      • Separate keys and their shifted values for more finely tuned layouts (can be done in xmodmap in Linux, but this isn't portable/cross platform)
        • May not act as expected in some programs as normally it is the computer that determines the shift's effect on the key, not the keyboard
        • Probably need to take special consideration into key sequences (eg pressing shift then x as opposed to x then shift)
  • Integrated pointing device
  • Bluetooth pedal
    • Needs to connect to the controller directly for most functions, so really only feasible with the custom controller
    • Need to verify keyboard's bluetooth controller can connect to two devices at once (PC and pedal(s))

Prototype

The Kinesis Advantages was found to natively support PS/2 output. This was tested using the PS/2 cable from a Kinesis Essential 132 (the 132 was also found to be capable of outputting USB using the Kinesis Advantages USB cable/board). The USB Kinesis Advantage is the first board that is going under the knife. Because of the relative simplicity of reading PS/2 data, this is the method that will be used.

PS/2 communication (according to the Arduino PS/2 library) only requires an interrupt pin and a generic IO pin. The WT12 requires a serial channel. These requirements are pretty basic, so any microcontroller should work fine. Additional IO might be desirable for a BT pairing button, but this feature could also be embedded into a special key combination on the keyboard itself.

Parts

  • Bluegiga WT12 Bluetooth module (serial only breakout board - $40, full breakout board - $50)
  • Microcontroller development board
    • Arduino (easy to use, PS/2 libraries) - $10-$50
    • ATmega32u4 based dev board (native USB HID output which can be used while plugged in and charging for improved reliability and charging speed) - $15-$40
    • MSP430 (specialize in low power, great for battery operation) - $5+
  • Logic level converter (PS/2 device requires 5v and WT12 requires 3.3v; microcontroller could use either) - $2
  • Power supply (for testing could use bench supply but USB charged Lithium Ion would be good to prototype too)

Reference

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