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 0~179: HIGH, TIM_CNT 180~199: 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 */