Hello, I am working at project of digital speed fan controller with LM2596 power switching converters. I would like to control and measure 4 computer fans channels.
In this project I would like to use 4 pwm outputs (Timer 1 and Timer 3) with 8 bit Fast PWM Mode at prescaller equal 1 ~62kHz (or something lower but not basic 1kHz or 490Hz, maybe about 25kHz to use this signal to control 4 wire fans - I don't know exactly yet). Also I would like to measure RPM of this fan channel. I found informations about Interrupt channels at Leonardo. I could have external interrupts at pins: 3, 2, 0, 1, 7. I've decided to use pins 2,0,1,7. In future I would like to use pin 3 maybe as PWM output if it is possible.
I am looking for some explanation how to do this in proper way. When I am using external interrupts could I change PWM frequency without harm for reading interrupts? Could somebody propose a way of reading this RPM in code or explain how to count RPM? I have little problem with understand it how it works.