Peter, thanks for your reply.
I have found this document:
Creating a variable frequency PWM output on Arduino UNO / by Sami Mughal, April 7, 2011 with other suggestion to program registers, but obviously for the UNO!
So I have tried is in a sketch:
// alternative mode for setting bits
// see http://www.arduino.cc/playground/Main/TimerPWMCheatsheet
//TCCR0B = TCCR0B & 0b11111000 | 0x01; //for timer 0, effects millis() and delay()
TCCR1B = TCCR1B & 0b11111000 | 0x01; //for timer 1, pin 9 and 10
TCCR2B = TCCR2B & 0b11111000 | 0x01; //for timer 2, pin 11 (and 3)
But that gives this error message from the compiler:
pwm_9_10_11_125Hz.ino: In function 'void setup()':
pwm_9_10_11_125Hz:37: error: 'TCCR2B' was not declared in this scope
I guess that there are only two PWM registers in the Arduino Leonardo?
I did not yet check with an oscilloscope what the outputs do with using TCCR1B and TCCR0B, will do so tomorrow :-)
Kind regards, Dick van Fulpen, Houten (NL)