I found that speed sensor option more useful for me than PS2 keyboard.
I have made same RC filter as for hall sensor on triggers (R48 R91 D27 C33), but for INT6 MCU pin. It is possible to use stock hall sensor.
There is one config variable - signal frequency (Hz) for 100kph.
Interrupt disabled every time after sample captured for save cpu time (calc freq 10Hz but sensor freq may be 200Hz)
Speed calc routine is calls from main loop every 100ms and contains division 32/16.
