ATtiny45 PWM Frequency Selection

Using Arduino Microcontrollers
14

The Tiny Core includes a (partial) hardware veneer that should make changing the "user timer" a bit easier. Give this a try...

#include <UserTimer.h>

void setup( void )
{
  UserTimer_SetToPowerup();
  UserTimer_SetWaveformGenerationMode( UserTimer_(Fast_PWM_FF) );
  UserTimer_ClockSelect( UserTimer_(Prescale_Value_1) );
  // Frequency is F_CPU / (1 * (0xFF+1))
  // (8 megahertz) / 256 = 31.25 kilohertz
}

void loop( void )
{
}

The code changes timer 0 when millis is on timer 1 and vice versa.