HCSR04 Ultrasonic Sensor Driver

HC_SR04 is a widely used ultrasonic ranging module. The module diagram is as follows

The module has four pins, namely VCC GND TRIG ECHO, where VCC GND is the power supply pin

TRIG is the ranging trigger pin, ECHO is the ranging input pin

The drive mode of this module is

The control port sends a high level of more than 10US, and then you can wait for the high level output at the receiving port. Once there is an output, you can start the timer. When this port becomes a low level, you can read the timer value, which is the time of this distance measurement, and then you can calculate the distance. By continuously measuring in this way, you can reach the value of your mobile measurement.

The module works as follows

(1) Use IO to trigger the ranging and provide a high-level signal of at least 10us;

(2) The module automatically sends 8 40khz square waves and automatically detects whether there is a signal return;

(3) When a signal is returned, a high level is output through IO. The duration of the high level is the time from the ultrasonic wave being emitted to the ultrasonic wave being returned.

(4 Calculate the test distance Test distance = (high level time * sound speed (340M/S))/2;

According to the working principle, we can choose two modes to drive

1. Use the interrupt + timer method, define ECHO as both the rising and falling edges can trigger interrupts. After trig is triggered, echo high level will interrupt and turn on the timer, echo low level will turn off the timer and count the timer count value

2. Use normal IO+timer mode, wait for echo response after triggering, turn on the timer when responding, and turn off the timer until echo returns to low, and get the time

1: This module should not be connected with power on. If it is to be connected with power on, connect the Gnd end of the module first. Otherwise, it will affect

Modules work.

2: When measuring distance, the area of ​​the object to be measured should be no less than 0.5 square meters and should be as flat as possible. Otherwise, the test results will be affected.

The detailed driver code is as follows

Hcsr04.c

1. #include "hcsr04.h"  

2.   

3.   

4. #define HCSR04_PORT GPIOB  

5. #define HCSR04_CLK RCC_APB2Periph_GPIOB  

6. #define HCSR04_TRIG GPIO_Pin_5  

7. #define HCSR04_ECHO GPIO_Pin_6  

8.   

9. #define TRIG_Send PBout(5)  

10. #define ECHO_Reci PBin(6)  

11.   

12. u16 msHcCount = 0; //ms count  

13.   

14. void Hcsr04Init(u32 NVIC_PriorityGroup,u32 PreemptionPriority,u32 SubPriority)  

15. {  

16.     u32 NVICtemp = 0; //Variables for NVIC controller  

17.     TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; //Generate a structure for timer settings  

18.     GPIO_InitTypeDef GPIO_InitStructure;  

19.     RCC_APB2PeriphClockCmd(HCSR04_CLK, ENABLE);  

20.       

21.     NVICtemp = NVIC_EncodePriority(NVIC_PriorityGroup, PreemptionPriority, SubPriority); //Interrupt priority variable decoding  

22.       

23.     //IO initialization  

24.     GPIO_InitStructure.GPIO_Pin =HCSR04_TRIG; //Send level pin  

25.     GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;  

26.     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; //Push-pull output  

27.     GPIO_Init(HCSR04_PORT, &GPIO_InitStructure);  

28.     GPIO_ResetBits(HCSR04_PORT,HCSR04_TRIG);  

29.       

30.     GPIO_InitStructure.GPIO_Pin = HCSR04_ECHO; //Return level pin  

31.     GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;  

32.     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD; //Pull-down input  

33.     GPIO_Init(HCSR04_PORT, &GPIO_InitStructure);      

34.     //Timer initialization using basic timer TIM6  

35.       

36.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE); //Enable the corresponding RCC clock  

37.     //Configure the timer infrastructure structure  

38.     TIM_TimeBaseStructure.TIM_Period = 1000; //Set the value of the auto-reload register period to load the activity at the next update event. Count to 1000 for 1ms  

39.     TIM_TimeBaseStructure.TIM_Prescaler = (72-1); //Set the prescaler value used as the TIMx clock frequency divisor 1M counting frequency 1US counting  

40.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM up counting mode  

41.     TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure); //Initialize the time base unit of TIMx according to the parameters specified in TIM_TimeBaseInitStruct  

42.       

43.     TIM_ClearFlag(TIM6, TIM_FLAG_Update); //Clear the update interrupt to avoid an interrupt being generated immediately after the interrupt is enabled  

44.     TIM_ITConfig(TIM6,TIM_IT_Update,ENABLE); //Enable timer update interrupt  

45.     NVIC_SetPriority(TIM6_IRQn,NVICtemp); //Set interrupt priority  

46.     NVIC_EnableIRQ(TIM6_IRQn); //Enable the corresponding interrupt  

47.       

48. }  

49. static void OpenTimerForHc() //Open the timer  

50. {  

51.     TIM_SetCounter(TIM6,0); //Clear count  

52.     msHcCount = 0;  

53.     TIM_Cmd(TIM6, ENABLE); //Enable TIMx peripherals  

54. }  

55.   

56. static void CloseTimerForHc() //Close the timer  

57. {  

58.     TIM_Cmd(TIM6, DISABLE); //Enable TIMx peripherals  

59. }  

60.   

61.   

62. //Timer 6 interrupt service routine  

63. void TIM6_IRQHandler(void) //TIM3 interrupt  

64. {  

65.     if (TIM_GetITStatus(TIM6, TIM_IT_Update) != RESET) //Check whether TIM3 update interrupt occurs  

66.     {  

67.         TIM_ClearITPendingBit(TIM6, TIM_IT_Update ); //Clear TIMx update interrupt flag   

68.         msHcCount++;  

69.     }  

70. }  

71.   

72. u32 GetEchoTimer(void)  

73. {  

74.     u32 t = 0;  

75.     t = msHcCount*1000; //Get MS  

76.     t += TIM_GetCounter(TIM6); //Get US  

77.     return t;  

78. }  

79.   

80. //Get ultrasonic distance measurement data once. There needs to be a period of time between two distance measurements to cut off the echo signal.  

81. void Hcsr04GetLength(u32* length)  

82. {  

83.     u32 t = 0;  

84.     float lengthTemp;  

85.     TRIG_Send = 1; //Send port high level output  

86.     DelayUs(10);  

87.     TRIG_Send = 0;  

88.     while(ECHO_Reci == 0); //Wait for the receiving port to output high level  

89.     OpenTimerForHc(); //Open the timer  

90.     while(ECHO_Reci == 1);  

91.     CloseTimerForHc(); //Close the timer  

92.     t = GetEchoTimer(); //Get time, resolution is 1US  

93.     lengthTemp = ((float)t/58);//cm  

94.     *length = (u32)lengthTemp;   

95. }  

Hcsr04.h

1. #ifndef __HCSR04_H  

2. #define __HCSR04_H  

3. #include "stm32f10x.h"  

4. #include "delay.h"  

5. #include "ioremap.h"  

6. #include "common.h"  

7.   

8.   

9.   

10.   

11.   

12. //Ultrasonic module initialization  

13. void Hcsr04Init(u32 NVIC_PriorityGroup,u32 PreemptionPriority,u32 SubPriority);  

14.   

15. //Ultrasonic module once distance acquisition  

16. //Return 0 Success  

17. //Return 1 if failed  

18. void Hcsr04GetLength(u32* length);  

19.   

20. #endif  

21.