Simple motor control with STM32 microcontroller

Outcome is this!

Experimental environment

The machine spec and motor information are described in the table.

The circuit is expressed as follows. This is based on the article about writing a schematic of a drone.

STM32 configuration and source code

Configuration

Choose TIM3 this time since Timer 3 can be used in all of STM32 series (ref).

I set the following configurations.

A screenshot of the above configuration is shown here. This is specified in a .ioc file.

PWM frequency is calculated as follows (ref).

$$ \mathrm{PWM \ frequency} = \frac{\mathrm{frequency \ of \ the \ clock}}{\mathrm{prescaler} \times \mathrm{counter \ period}}$$

※ As for STM32CubeIDE setting, we should subtract $1$ from the prescaler and the counter period values because they are 0-based (ref).

Here, the prescaler is $1$, the counter period is $256$, and the frequency of the clock is $8 \, \mathrm{Mhz}$, thus the PWM frequency is $31.25 \, \mathrm{kHz}$.

After setting the above configuration, automatically PA6 was chosen for the timer output PIN.

Referring to PIN layout shown below, we need to connect D12 to use PA6 for timer 3 channel 1.

Source code

The main source code is uploaded on github repository.

The point is the generation of PWM signals depending on time and creates a sine wave for PWM input. The data variable ranges from $95$ to $255$ and the period of the sine wave is around $6.28$ seconds.

  while (1)
  {
	double t = HAL_GetTick() / 1000.0;  // ms -> s
	const double gain = 80.0;
	const double offset = 175.0;
	int data = gain * sin(t) + offset;

	__HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_1, data);
	printf("data: %d \n", data);
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }

The function __HAL_TIM_SET_COMPARE() can change the PWM value dynamically (ref).

Reference

Some references are in Japanese but are quite well documented.

• STM32でDCモータを回す – 元Web屋のマイクロマウス製作記 Part.18
• STMマイコンでPWMを出力するときのメモ（HAL, CubeMX）
• Getting Started with STM32 – Timers and Timer Interrupts