It configures the timer to operate in single slope fast PWM mode and sets the prescaler to the mode indicated on the function argument. The pwm91011configure function must be called previously to the call of any other function associated to this timer. It can uses all three Timer 1 compare channels to generate PWM signals at Arduino pins 9, 10 and 11. The code associated to timer 1 includes 4 functions and several defines. The sketch includes the needed code to operate 5 pins associated to Timers 1 and 4 in fast PWM modes. I have put together all the above methods to generate PWM in a FastPWM Arduino sketch. Similar tables can be found for channels B and D. The complementary signals can have some deadband between them so that one signal, and its complement are never active at the same time. Mode 11 will give a complementary output whereas mode 01 gives two complementary PWM outputs at different pins. Normal PWM operation corresponds to mode 10. That gives, using the 16MHz Arduino Leonardo system clock, the fiveclock and single slope frequencies shown below for standard 8, 9 and 19 bit modes: The timer gets its clock from the global MCU prescaler that provides five frequencies from the system clock. The other 6 additional PWM modes use programmable terminal counts that can be any 16 bit value and is not restricted to 255, 511 or 1023. Three bit modes 8, 9 and 10 for single and dual slope PWM gives a total of 6 PWM modes. You can also have 9 bits and 10 bits PWM modes with 5 terminal counts that can operate on single and dual slope modes. As single slope is faster that dual slope, it is also called Fast PWM mode. The fastest PWM mode available is single slope 8 bits counting between 0 and 255. The timer has several modes of operations that include 12 PWM modes. That means that it can count from 0 up to 65535 before overflowing. Timer 1 is based arround a 16 bit counter. You should take care if you use the Servo library because it also uses Timer 1. Timer 1 is a good candidate as it has three available compare channels and don't mess with Arduino delay functions. If the maximum 976 Hz that stock Arduino analogWrite is not enough, we need to develop our own PWM functionality.
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