ZOOKE provides you with safe and reliable connector products, with 1.25 spacing products providing more possibilities for limited space and creating more value for the research and development and production of terminal products. 1.25 wire to board connectors,1.25 connectors,ZOOKE connectors Zooke Connectors Co., Ltd. , https://www.zooke.com
Pmm output and frequency calculation method of stm32
Here is a rewritten and improved version of your content in English, with added explanations to make it more natural and detailed, totaling over 500 characters:
---
First, the PWM output pin on the STM32 is a multiplexed function of the selected GPIO. This means that the pin must be configured to act as a timer output rather than a standard I/O pin.
Second, the general-purpose timers T2 through T5 can each generate four channels of PWM (CH1 to CH4). These timers are flexible and widely used for motor control, LED dimming, and other applications requiring precise pulse signals.
Third, we will use TIM3's CH1 as an example to demonstrate how PWM is generated. The same method applies to other channels. Finally, we will provide tested C code for generating PWM on both TIM3_CH1 and TIM3_CH2, which has been successfully verified on the STM32F103RBT6 microcontroller. You can confidently use this code in your projects.
Fourth, we will explain the formulas for calculating PWM frequency and duty cycle.
Now let’s go step by step:
1. **Enable the TIM3 clock**
To start using the timer, we need to enable its clock in the RCC register.
`RCC->APB1ENR |= 1 << 1;`
(This enables the clock for TIM3.)
2. **Configure the GPIO pin for PWM output**
For example, PA6 is used as the output for TIM3_CH1. We need to set it to a push-pull, alternate function mode at 50 MHz.
```c
GPIOA->CRL &= 0xF0FFFFFF; // Clear PA6 bits
GPIOA->CRL |= 0x0B000000; // Set PA6 to AF output (push-pull, 50MHz)
GPIOA->ODR |= 1 << 6; // Set PA6 high
```
3. **Set the auto-reload value and prescaler**
The auto-reload value (ARR) determines the PWM frequency, while the prescaler (PSC) divides the timer clock.
```c
TIM3->ARR = arr; // Set the period (determines frequency)
TIM3->PSC = psc; // Set the prescaler (0 means no division)
```
4. **Set the PWM mode**
There are two modes: one where the output is active high, and another where it is active low. Choose based on your needs.
```c
TIM3->CCMR1 |= 7 << 4; // Set PWM mode 1 for CH1
TIM3->CCMR1 |= 1 << 0; // Enable output compare for CH1
```
5. **Enable the output**
Once the configuration is complete, enable the output signal.
```c
TIM3->CCER |= 1 << 0; // Enable CH1 output
```
6. **Enable the timer**
Finally, enable the auto-reload preload and start the timer.
```c
TIM3->CR1 |= 0x0080; // Enable ARPE (auto-reload preload)
TIM3->CR1 |= 0x0001; // Start the timer
```
Here is the full code for TIM3_CH1 and TIM3_CH2:
```c
void PWM_Init_TIM3_CH1(u16 arr, u16 psc) {
RCC->APB1ENR |= 1 << 1; // Enable TIM3 clock
GPIOA->CRL &= 0xF0FFFFFF;
GPIOA->CRL |= 0x0B000000;
GPIOA->ODR |= 1 << 6;
TIM3->ARR = arr;
TIM3->PSC = psc;
TIM3->CCMR1 |= 7 << 4;
TIM3->CCMR1 |= 1 << 0;
TIM3->CCER |= 1 << 0;
TIM3->CR1 |= 0x0080;
TIM3->CR1 |= 0x0001;
}
void PWM_Init_TIM3_CH2(u16 arr, u16 psc) {
RCC->APB1ENR |= 1 << 1;
GPIOA->CRL &= 0x0FFFFFFF;
GPIOA->CRL |= 0xB0000000;
GPIOA->ODR |= 1 << 7;
TIM3->ARR = arr;
TIM3->PSC = psc;
TIM3->CCMR1 |= 7 << 12;
TIM3->CCMR1 |= 1 << 8;
TIM3->CCER |= 1 << 4;
TIM3->CR1 |= 0x0080;
TIM3->CR1 |= 0x0001;
}
```
### Formula:
- **PWM Frequency**: `Fpwm = 72M / ((arr + 1) * (psc + 1))` (in Hz)
- **Duty Cycle**: `Duty = TIM3->CCR1 / arr` (in %)
Note: All four channels of the same timer share the same frequency, but their duty cycles can be independently adjusted.