Introduction:
Pulse Width Modulation (PWM) is a widely used technique for controlling the brightness of LEDs in embedded systems. In this blog post, we'll delve into the world of PWM control using the ARM mbed platform on the STM32 microcontroller. By the end of this guide, you'll have a solid understanding of how to implement PWM to achieve precise control over the intensity of your LEDs.
Understanding PWM:
PWM works by varying the duty cycle of a square wave signal to control the average power delivered to a device. For LEDs, this means adjusting the time the LED is on versus off to control its brightness. In the context of mbed and STM32, we'll be manipulating the PWM signals to regulate LED brightness.
Setting Up mbed and STM32:
1. **Hardware Setup:**
Ensure you have an STM32 development board and an LED connected to one of the PWM-capable pins.
2. **mbed Configuration:**
Create an mbed project and import the STM32 library. Configure your project settings to match your specific STM32 board.
Coding the PWM Control:
Now, let's get into the code. Below is a basic example using the mbed API for PWM control:
```cpp
#include "mbed.h"
// Define the PWM pin and LED
PwmOut led(PA_5);
int main() {
// Set the PWM frequency and initialize duty cycle
led.period(0.01); // 100Hz frequency
led.write(0.5); // 50% duty cycle (initial brightness)
while(1) {
// PWM fading effect - increase brightness
for(float brightness = 0.1; brightness < 1.0; brightness += 0.1) {
led.write(brightness);
wait(0.2); // Adjust the delay for your desired fading speed
}
// PWM fading effect - decrease brightness
for(float brightness = 1.0; brightness > 0.1; brightness -= 0.1) {
led.write(brightness);
wait(0.2); // Adjust the delay for your desired fading speed
}
}
}
```
Explanation:
- **PwmOut:** This class is part of the mbed API and is used to create a PWM output on a specified pin.
- **led.period():** Sets the PWM signal period, controlling the frequency of the signal.
- **led.write():** Sets the duty cycle, determining the LED brightness.
- **wait():** Pauses the program for a specified amount of time.
Feel free to adapt this code to your specific needs and explore other PWM features provided by mbed and STM32.
Conclusion:
By incorporating PWM control into your LED projects with mbed and STM32, you can achieve dynamic lighting effects and precise brightness adjustments. This fundamental skill opens the door to more advanced applications in embedded systems and IoT projects. Happy coding!