2015-08-11 (Tu) Wrist Mounted Chording Keyboard

Between the servos and keyboard a lever will be needed. This has been referred to as the servo lever arm. Consideration was given to using a socket and threaded rod here the same way it was done with the wrist mount but a fully modeled lever was decided upon due to simplicity. A parametric model was programmed which could have the relevant sizes altered as necessary. Primarily the adjustments were the:
  • length of the lever.
  • radius of the hole for the servo horn.
  • radius and length of the servo slot hole
  • radius of the hinge hole.

Rotating view of servo lever arm

A lot of deliberation took place on how to approach the programming. Numerous issues were apparent with the current direction. The previous mindset was to program an Arduino Pro Mini to interpret switch data from the keyboard and output serial data to a Bluefruit. This approach was not bad but it meant that a wired keyboard wasn't possible in the meantime. A wired keyboard would be possible only with hardware additions and programming changes. During debugging raw serial data would have to be interpreted through a serial port rather than actual typing so no typing would take place until the program was finished and painstakingly debugged. Doable but tedious.

The solution was to switch programming to an Arduino Micro which supports keyboard commands and doesn't need the ASCII commands used by the Bluefruit. The Micro is substantially more expensive than a Pro Mini. This will allow anyone who only wants a wired keyboard to implement the code immediately with minimal hardware. It will also allow the hardware to be used while debugging so practice can start before the project is finalized.

Once the keyboard is debugged a revision to the program will send the ASCII commands as originally intended but through a SoftwareSerial port instead. This means the Arduino will simultaneously be sending keyboard commands through the standard USB port as well as the SoftwareSerial port into the Bluetooth. Anyone should have little trouble connecting the keyboard. If that goes well the serial data coming into the SoftwareSerial port, like connecting a UART RFID reader, would be turned into keyboard data for the USB keyboard portion. This would allow RFID tags to be "typed." The final step, which is unlikely, would be to translate the incoming UART data through Bluetooth as well.

To do:
  • Wire Arduino Micro with RJ45 end
  • Program Arduino Micro to act as wired keyboard
  • Add SoftwareSerial port to Micro to send ASCII data to Bluefruit.
  • Use the  SoftwareSerial port to "type" data to the USB keyboard.
  • Route incoming data to Bluefruit as well.
  • Secure Ethernet wire with a cable clamp
  • Make model and OpenSCAD code public
  • Write keyboard code

The rest of the posts for this project have been arranged by date.

First time here?

Completed projects from year 1.
Completed projects from year 2

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2015-08-10 (M)