![]() ![]() Each timer has two output compare registers that control the PWM width for the timer's two outputs: when the timer reaches the compare register value, the corresponding output is toggled. By manipulating the chip's timer registers directly, you can obtain more control than the analogWrite function provides.The AVR ATmega328P datasheet provides a detailed description of the PWM timers, but the datasheet can be difficult to understand, due to the many different control and output modes of the timers.A word on the relationship between the Arduino language and the datasheet may be in order here.The Atmega 168/328 timers.The ATmega328P has three timers known as Timer 0, Timer 1, and Timer 2. Finally, it's difficult to determine the appropriate constants for a particular duty cycle and frequency unless you either carefully count cycles, or tweak the values while watching an oscilloscope.A more elaborate example of manually PWMing all pins may be found.Using the ATmega PWM registers directlyThe ATmega168P/328P chip has three PWM timers, controlling 6 PWM outputs. A second disadvantage is you can't leave the output running while the processor does something else. One major disadvantage is that any interrupts will affect the timing, which can cause considerable jitter unless you disable interrupts.
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