Reefwing PWM

This library is a fork of MD_PWM by MajicDesigns. Apart from cosmetic changes, the main difference is to increase the maximum number of concurrent PWM pins to 6 (MAX_PWM_PIN), and to reduce the maximum PWM Frequency (MAX_FREQUENCY) to 100 Hz.

Library for AVR PWM on arbitrary pins

This library is designed to provide 'software' PWM output for any digital pin.

Important Notes:

• This library uses AVR TIMER1 or TIMER2 to implement the interrupt driven clock, selectable in the library header file. The library defaults to TIMER2.
• This library has been tested on Arduino Uno and Nano only (i.e., Arduino boards with the ATMega328P processor).

Implementation

This library implements user defined frequency PWM output for any digital pin software limited to MAX_FREQUENCY Hz.

The TIMERn is set for 255 times this frequency (eg, 200Hz becomes 51kHz). This causes the TIMERn interrupt routine to be called 255 times for each PWM cycle and, depending on where it is in the cycle, allows the software to set the digital output pin to LOW or HIGH, thus creating the desired PWM signal.

The duty cycle can be changed smoothly by changing the set point at which the digital transition occurs. The new duty cycle takes effect at the start of the next PWM transition.

TIMERn is a global resource, so each object instance of class is driven from the same TIMERn interrupt. The constant MAX_PWM_PIN is used to set limits the global maximum for instances allowed to be processed by the interrupt.