Reference for Wiring version 1.0 Build 0100+ If you have a previous version, use the reference included with your software. If see any errors or have any comments, let us know.
... // sets the PWM output frequency prescale to // 1/8th of the main clock frequency // for the analogWrite() command setPWMPrescale(29, CLOCK_PRESCALE_8); ...
|Description||The setPWMPrescale() method sets the PWM output frequency of a PWM output pin. On Wiring v1 boards the PWM capable pins are: 29, 30, 31, 35, 36 and 37. On Wiring S board the PWM capable pins are: 4, 5, 6, 7, 19 and 20. Possible frequency Prescale values are:
CLOCK_PRESCALE_64 (F_CPU/64 default value),
IMPORTANT Note: PWM pins are internally grouped/managed by timers, a single timer can handle 2 or 3 pins, which means that changing operation settings like resolution or prescale for one pin will change it as well for the pins sharing the same timer. For example setting PWM bit resolution to 10 bits for pin 29 on the Wiring v1 boards will automatically change it for pins 30 and 31 (29, 30 and 31 are controlled by the same timer). On Wiring v1 boards timer PWM pin groups are: [29, 30, 31] and [35, 36, 37]. On Wiring S board timer PWM pin groups are: [4,5] [6,7] and [19, 20].