Description
Pulse Width Modulation is one of the important functions of timer. PWM is a technique to control analogue circuits with digital output from microcontroller.
As you all know that an Analogue signal is the one whose value varies continuously with time whereas digital signals can only be either high or low. PWM is used for generating an analogue signal using a digital source.
PWM consist of two main components:-
1.) Duty cycle
2.) Frequency
Duty cycle describes the amount of time, the signal is in HIGH state as a percentage of total time, it takes to complete one cycle. Frequency describes how fast the PWM completes a cycle and therefore how fast it switches between HIGH and LOW.
By cycling a digital signal ON and OFF at a fast enough rate and at a certain duty cycle, the output will appear like a constant voltage analogue signal. For eg: To create a 2V signal from a digital source which is either HIGH(5V) or low (0). We can use PWM with duty cycle of 40% here. This 40% duty cycle would yield an average voltage of 5×0.4=2V.
Duty cycle of 25%
Duty cycle of 75%
Some Insight into the Code:-
if (!(HAL_GPIO_ReadPin (GPIOC, GPIO_PIN_13))) // if the user button is pressed
{
while (!(HAL_GPIO_ReadPin (GPIOC, GPIO_PIN_13))); // wait for the button to be released
htim3.Instance->CCR1 = increment; // increase the pulse width in the steps of 10
increment+=10; // increment in 10 steps or by 10% for the duty cycle
if (increment>100) increment =0; // if increment is > 100 than reset its value to 0
}
Result
Duty cycle 70%
Duty Cycle 50%
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How to generate a center aligned pwm.
I am running a Nucleo-64 with a STM32F401RE on it and the PWM frequency, as clocked by APB1, is nothing compared to what it should be. Say APB1 clock frequency is 84MHz and the pre-scale is 20 I get 19.84MHz on the PWM output?