TeensyKey

Keyboard firmware for Teensy 3.1

This firmware runs on the Teensy 3.1 microcontroller (and maybe other Arduino platforms?) and supports a range of features suited to Atreus like keyboards such as:

• Tapping modifiers Tapping the key produces a keystroke like space or return. Holding the key and hitting a normal key (within the timeout period) makes the key act like a modifier.

• Sticky modifier keys The shift keys can act like normal shift keys if held down and then a normal key is hit. Or, a single tap causes the next key to be shifted. Or a double tap acts like caps-lock.

• Layers Keys can have more than the normal two meanings (eg 'a' and 'A' or '1' and '!'). Layer modifiers select the meanings. The layers currently implemented include a layer of punctuation keys and a layer of number keys (and media keys). This is necessary because the Atreus only has 42 keys but normal keyboards have 80-100 keys.

These ideas are based on similar features found in the Atreus firmware, in the TMK Keyboard firmware and in Edgar Matias's Half Qwerty. I made my own implementation because I was having trouble porting TMK and Atreus to the Teensy 3.0.

Future directions

• It is traditional to put the keymap in a separate .h file and select the keymap at build time.

• The software does a lot of busy waits. It should go into a low power sleep mode instead. (I want to get a power meter first so that I can see if this matters.)

• Instead of running in the main loop, it may be better to scan in a timer interrupt so that I can run another program in the foreground. Better yet would be to get the matrix to generate interrupts when a key is pressed so that if nothing is happening the processor is completely asleep.

• I keep thinking about adding a mini joystick and sending mouse move commands. I am not sure if there is any point unless I also have mouse buttons though.

• The binary is far larger than it should be. I need to be smarter about which parts of the Teensy library I link in.