ECE3730J RC3_LAB4

For this RC, we will go through Lab 4 in detail.

CubeMX

We need to generate PWM signal on PB14(embeded with an LED D1, or D2 if you like)

when the PB14 output LOW, D1 will light up.

In STM32, Input Capture and Output Compare is configured in Timer channels.

Let’s check which Timer is connected to PB14

It’s the CH2N channel of timer 1.

Then we configure timer 1.


Prescaler: 7200-1
Counter Period: 200-1 (50Hz)
Pulse: 180 (duty cycle of 90%; TIM_CNT 0179: HIGH, TIM_CNT 180199: LOW)
CHN Polarity: LOW (needed for CHN)

CHxN is the complementary channel of CHx in Timer1.
If the polarity of CHxN and CHx are different, the two channels will follow the same output pattern, otherwise they will be complementary

Also remember to configure PB12 (SW4) as GPIO_Input.

You can try to use Input Capture to capture the press action of the button (as indicated in lab manual, i.e. connecting PB12 to PA0).

Code

Init PWM in main():

/* USER CODE BEGIN 2 */
HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2);
HAL_TIMEx_PWMN_Start(&htim1, TIM_CHANNEL_2);
/* USER CODE END 2 */

Change PWM duty cycle:

void ChangeDutyCycle(int pulse_width)
{
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_2, pulse_width);
    // htim1.Instance->CCR2 = pulse_width;
}

Get the press/release action of the button (PB12):

int pressed = 0;
   /* USER CODE BEGIN WHILE */
   while (1) { // main loop
       /* USER CODE END WHILE */
       /* USER CODE BEGIN 3 */
       if (!HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) && pressed == 0) {
           pressed = 1;
           // what to do when pressed
       }
       else if (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) && pressed == 1) {
           pressed = 0;
           // what to do when releassed
       }
   }
   /* USER CODE END 3 */