[STM32 learning] (22) STM32 realizes 360 degree rotary encoder

360 degree The object of rotary encoder is as follows ：

KY-040 Rotary encoder module

  Working voltage ：5V

Number of pulses per cycle ：20

The rotary encoder can count the number of output pulses in the process of positive and negative rotation by rotation , Rotation counting is not like potentiometer , This rotation count is unlimited . Cooperate with the keys on the rotary encoder , It can be reset to the initial state , From 0 Start counting .

  working principle ： Incremental encoder is a kind of rotary sensor that converts rotary displacement into a series of digital pulse signals . These pulses are used to control the angular displacement . stay Eltra The conversion of angular displacement in the encoder adopts the photoelectric scanning principle . The reading system consists of a radial dividing plate composed of alternating light transmission windows and light tight windows （ Code disk ） Based on the rotation of , At the same time, it is vertically illuminated by an infrared light source , Light projects the image of the code disk onto the surface of the receiver . The receiver is covered with a diffraction grating , It has the same window width as the code disk . The work of the receiver is to feel the changes caused by the rotation of the disc , Then convert the light change into the corresponding electrical change . Then raise the low-level signal to a higher level , There is no square pulse without any interference , This must be handled by electronic circuits . The reading system usually adopts differential mode , That is, the two waveforms are the same, but the phase difference is 180° Compare different signals , In order to improve the quality and stability of the output signal . The reading is based on the difference between the two signals , Thus, the interference is eliminated .

The incremental encoder gives two-phase square wave , Their phase difference 90°, Often referred to as A Channels and B passageway . One of the channels gives information related to speed , meanwhile , Compare the signals of two channels in sequence , Get information about the direction of rotation . There is also a special signal called Z Or zero channel , This channel gives the absolute zero position of the encoder , This signal is a square wave and A The center lines of the channel square waves coincide .

 

Now realize the detection of this incremental encoder Positive rotation still reverse

Here we use read IO To read data , To determine whether it is a forward turn or a reverse turn .

Single chip model ：STM32L052K8*

connection ：CLK  Pick up   PA0

            DT    Pick up   PA1

            SW  Pick up   PA2

int main(void)
{
  /* USER CODE BEGIN 1 */
	unsigned char dt;
	unsigned char clk,key;
  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  /* USER CODE BEGIN 2 */
	printf("\n\r****wantin****\n\r");
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  printf("\n\**************\n\r");
	  clk = HAL_GPIO_ReadPin(DT_GPIO_Port,DT_Pin);
	  dt = HAL_GPIO_ReadPin(DT_GPIO_Port,DT_Pin);
	  key = HAL_GPIO_ReadPin(SW_GPIO_Port,SW_Pin);
	  if(1 == clk)
	  {
		  printf("\n\clk == 1\n\r");
	  }
	  else
	  {
		  printf("\n\clk == 0\n\r");
	  }
	  if(1 == dt)
	  {
		  printf("\n\dt == 1\n\r");
	  }
	  else
	  {
		  printf("\n\dt == 0\n\r");
	  }
	  if(1 == key)
	  {
		  printf("\n\key == 1\n\r");
	  }
	  else
	  {
		  printf("\n\key == 0\n\r");
	  }
	  HAL_Delay(1000);
  }
  /* USER CODE END 3 */
}

 

In terms of implementation effect , Not ideal ：

Whether you turn forward or backward ,CLK and DT The level of these two pins , All are successful 0、1 alternate , And the two levels are the same , It is impossible to distinguish between forward rotation and reverse rotation .

And then , Plug it in , Use an oscilloscope to test the waveform generated by these two pins . The effect is as follows ：

Acquisition interrupted 0 mouth , And then clk The signal

Waveforms of forward rotation ： The yellow line is clk, The blue line is dt

Falling edge trigger , Collected level   All for Low level   clk = 0   dt = 0;

Inverted waveform ： The yellow line is clk, The blue line is dt

Falling edge trigger , Collected level   clk = 0   dt = 1;

It can be seen from the waveform that , There is waveform difference between positive and negative , How to realize forward and reverse detection , Interrupt can be used to realize .

Adopt the falling edge trigger method to collect the changes of waveform .

int main(void)
{
  /* USER CODE BEGIN 1 */
	unsigned char dt;
	unsigned char clk,key;
  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  /* USER CODE BEGIN 2 */
	printf("\n\r****wantin****\n\r");
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  printf("\n\**************\n\r");
	  if(10 == spped_counter)
	  {
		  printf("\n\*** Positive rotation ***\n\r");
	  }
	  else
	  {
		  printf("\n\*** reverse ***\n\r");
	  }
//	  clk = HAL_GPIO_ReadPin(DT_GPIO_Port,DT_Pin);
//	  dt = HAL_GPIO_ReadPin(DT_GPIO_Port,DT_Pin);
//	  key = HAL_GPIO_ReadPin(SW_GPIO_Port,SW_Pin);
//	  if(1 == clk)
//	  {
//		  printf("\n\clk == 1\n\r");
//	  }
//	  else
//	  {
//		  printf("\n\clk == 0\n\r");
//	  }
//	  if(1 == dt)
//	  {
//		  printf("\n\dt == 1\n\r");
//	  }
//	  else
//	  {
//		  printf("\n\dt == 0\n\r");
//	  }
//	  if(1 == key)
//	  {
//		  printf("\n\key == 1\n\r");
//	  }
//	  else
//	  {
//		  printf("\n\key == 0\n\r");
//	  }
	  HAL_Delay(1000);
  }
  /* USER CODE END 3 */
}

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)  // External interrupt   Callback function 
{
	if(GPIO_Pin == CLK_Pin) // If any change is detected, come in and deal with it 
	{
		if(HAL_GPIO_ReadPin(CLK_GPIO_Port,CLK_Pin) == HAL_GPIO_ReadPin(DT_GPIO_Port,DT_Pin))  //clk pb0 == dt pb1
		spped_counter=10;		//	 Express   Positive rotation 
		else
		spped_counter=100;		//	 Express   reverse 
		
	}
}

 

 

The effect is as follows ：