ShiftPWM is a library/class for Arduino (tested on ESP32 only) to generate a PWM signal over a shift register (74HC595)

• copy ShiftPWM.h and ShiftPWM.cpp in the same folder of your program
• add include "ShiftPWM.h"
• Create instance of ShiftPWM by specifying duty cycles in Duties struct (can be updated later)
• Create a timer (preferably 1MHz), in its handler call ShiftPWM::Calculate() which returns a byte
• Write the byte returned from Calculate() to the shift register
• [ESP] To make timer creation simpler include ESPTimerHelper.h then call StartTimer(SetTimer(TIMER_INDEX,TIMER_HANDLER))

The class doesn't write the value to shift register anymore but returns a value, this is done to make it compatible with other environments (the ones that don't have pinMode, digtalWrite...etc)