Teensy LC != the fastest Van

Handwired MiniVan Keyboard with Teensy LC

• PJRC Teensy LC
• ARM Cortex-M0+ (MKL26Z64VFT4)
• 48MHz clock speed
• 3.3v logic
• TMK firmware
• Schottky diodes
• 4x12 matrix

This is a hand wired keyboard running TMK on a Teensy LC board. There is a bug in the compiler or libraries that causes the 30 microsecond delay after setting the row to be executed as a 1 millisecond delay instead. This was causing a single matrix scan to take 4 milliseconds. Replaced the delay with a small loop that toggles the status LED connected to pin 13. Reduced the number of loops so that a single matrix scan is about 101 microseconds. Which is about 9900 scans per second, about twice as fast as TMK on an AtMega32U4.

Example of the files modified for TMK https://gist.github.com/di0ib/4ad961f1f7935f05ace7045cbee50b14 

Graphs of matrix scanning times of other firmware here.

The Teensy 3.0 is even faster.