Briefly describe the method of using STM32 timer to count and control the orthogonal encoder

As shown in the figure, each TIMER of STM32 has an orthogonal encoder input interface. TI1 and TI2 are input filtered, and edge detection generates TI1FP1. TI2FP2 is connected to the encoder module. By configuring the working mode of the encoder, the encoder can be counted forward/reverse.

 
As shown in the figure below, the encoder uses two-phase signals A and B, but I only need to count the TI1 signal (the first line). I just discovered this error. It turns out that counting both signals results in more than 100 pulses (100-line photoelectric encoder) in one rotation of the encoder disk. By comparing the two level signals through the STM32 encoder module, it is easy to calculate the operation of the encoder.

 
The following is my debugged OK code:

1. 
   

2. void Encoder_Configration(void)
   

3. {
   

4. GPIO_InitTypeDef GPIO_InitStructure;
   

5. TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
   

6. TIM_ICInitTypeDef TIM_ICInitStructure;
   

7. 
   

8. //PC6 A phase PC7 B phase
   

9. GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
   

10. GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    

11. GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
    

12. GPIO_Init(GPIOC,&GPIO_InitStructure);
    

13. 
    

14. 
    

15. 
    

16. 
    

17. 
    

18. 
    

19. TIM_TimeBaseStructure.TIM_Prescaler = 0x0; // No prescaling 
    

20. TIM_TimeBaseStructure.TIM_Period = 10000; 
    

21. TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    

22. TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
    

23. TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);
    

24. 
    

25. TIM_EncoderInterfaceConfig(TIM8, TIM_EncoderMode_TI12, 
    

26. TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);
    

27. TIM_ICStructInit(&TIM_ICInitStructure);
    

28. TIM_ICInitStructure.TIM_ICFilter = 6;//ICx_FILTER;
    

29. TIM_ICInit(TIM8, &TIM_ICInitStructure);
    

30. 
    

31. // Clear all pending interrupts
    

32. TIM_ClearFlag(TIM8, TIM_FLAG_Update);
    

33. TIM_ITConfig(TIM8, TIM_IT_Update, ENABLE);
    

34. //Reset counter
    

35. TIM2->CNT = 0;
    

36. 
    

37. TIM_Cmd(TIM8, ENABLE); 
    

38. 
    

39. }
    

40. 
    

41. n_Counter = TIM_GetCounter(TIM8);
    

42. Diled_Disp_Num((float)n_Counter);
    

Another point worth noting is that the STM32 timer is 16 bits, which means it can only count to 65535. There are two ways to do this. One is to use two timers in a chained manner to expand 16 bits to 32 bits. Another simple method is to enable the overflow interrupt of the timer. Each interrupt represents that the encoder has run a specific angle.

For example, if the encoder has 400 lines, set the ARR register to 400. Each overflow interrupt represents that the motor has turned a circle, and so on.

In addition, the detection of input pulses is actually similar, except that an external trigger module is used inside the STM32 to implement it. As shown in the purple box in Figure 1, the encoder module should be an upgrade of this module. The following is the configuration code:

1. 
   

2. void TIM3_ETR_GetDropCounts_Configuration(void)
   

3. { 
   

4. GPIO_InitTypeDef GPIO_InitStructure;
   

5. TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
   

6. //test PA0 TIM8_ETR
   

7. GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
   

8. GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;;
   

9. GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
   

10. GPIO_Init(GPIOD, &GPIO_InitStructure);
    

11. 
    

12. TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
    

13. TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
    

14. TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
    

15. TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    

16. TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); // Time base configuration
    

17. 
    

18. TIM_ETRClockMode2Config(TIM3, TIM_ExtTRGPSC_OFF, TIM_ExtTRGPolarity_NonInverted, 0);
    

19. 
    

20. TIM_SetCounter(TIM3, 0);
    

21. 
    

22. TIM_Cmd(TIM3, ENABLE);
    

23. }