Source: Paul Stoffregen, FreqCount vs FreqMeasure

Paul Stoffregen's libraries for Teensy and “standard” Arduinos (not M0):

• FreqCount Library:
  • About: https://www.pjrc.com/teensy/td_libs_FreqCount.html
  • Github: https://github.com/PaulStoffregen/FreqCount
• FreqMeasure Library:
  • About: https://www.pjrc.com/teensy/td_libs_FreqMeasure.html
  • Github: https://github.com/PaulStoffregen/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/

The configuration of timers in ARM cortex M processors such as SAMD21 is somewhat more complex. The links below may help to understand the timer/counter configurations.

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

• 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