Source: Paul Stoffregen, FreqCount vs FreqMeasure

A good introduction on timer interrupts of AVR MCs is given by Amanda Ghassaei on Instructables: http://www.instructables.com/id/Arduino-Timer-Interrupts?ALLSTEPS

• Paul Stoffregen (Teensy, Freescale)
  • FreqCount Library: https://www.pjrc.com/teensy/td_libs_FreqCount.html
  • FreqMeasure Library: https://www.pjrc.com/teensy/td_libs_FreqMeasure.html

• Max Bader (M0, zero): https://github.com/maxbader/arduino_tools
  • timer_m0_tc_counter
  • timer_m0_tc_interrupt
  • timer_m0_tcc_interrupt

• Nonsintetic (M0, zero): https://gist.github.com/nonsintetic/
  • ArduinoZeroTimer

• Arduino Forum: Arduino ZERO Timer Interrupts