Openharmony South learning notes - hi3861+hc-sr04 ultrasonic testing

Preface

Recently participated in the Lichuang training camp , use Hi3861 Be a robot dog , Then continue to study for a period of time OpenHarmony Device development learning , The ultrasonic module has not been used in the previous notes , In this training camp , I intend to try in Hi3861 try .

Module introduction

The manufacturer's manual is shown below , The author bought 2022 paragraph , Links are as follows ：「 Ultrasonic ranging module HC-SR04 ultrasonic sensor Support compatibility UNO R3/51/STM32」.

The module supports four modes to obtain distance , It can be selected through the resistance setting on the back .

1. GPIO Pattern

Sequence diagram

This mode requires Hi3861 Of the two IO Mouth comes with the ultrasonic module TRIG and ECHO Two feet communicate .

Communication process

According to the manufacturer's information , The communication flow of this module is as follows ：
1. The main control chip and TRIG Connected IO Configured for output mode , And ECHO Connected IO Configured as input mode ;
2.MCU to TRIG Pin output is greater than 10us High level pulse of ;
3. Module through ECHO The pin returns a high-level pulse signal ;
4. Master record ECHO Pin high level pulse time T And substitute it into the formula .

Code

This code refers to Runhe intelligent tracking obstacle avoidance car sample code . The author here uses the vitality School of intellectual education , Some interface definitions are different .

// An highlighted block

#define Echo  8   //Echo //GPIO8
#define Trig  7   //Trig //GPIO7
#define GPIO_FUNC 0

float GetDistance  (void) {
    
    static unsigned long start_time = 0, time = 0;
    float distance = 0.0;
    IotGpioValue value = IOT_GPIO_VALUE0;
    unsigned int flag = 0;
            /* =============== GPIO Communication mode process  1 initialization GPIO======================================== */
    IoTIoSetFunc(Echo, GPIO_FUNC);// Set up Echo Connect IO For the ordinary GPIO Pattern , No reuse 
    IoTGpioSetDir(Echo, IOT_GPIO_DIR_IN);// Set up Echo Connect IO Is the input mode 
    IoTGpioSetDir(Trig, IOT_GPIO_DIR_OUT);// Set up Trig Connect IO For output mode 
            /* =============== GPIO Communication mode process  2 Output start signal ======================================== */
    IoTGpioSetOutputVal(Trig, IOT_GPIO_VALUE1);// pull up Trig
    IoTUdelay(20);//20us
    IoTGpioSetOutputVal(Trig, IOT_GPIO_VALUE0);// Pull it down Trig
           /* =============== GPIO Communication mode process  3 testing Echo High level time of pin output ======================================== */
    while (1) {
    
        IoTGpioGetInputVal(Echo, &value);// Read Echo The level state of the pin 
        if ( value == IOT_GPIO_VALUE1 && flag == 0) {
    // If it's high 
            start_time = IoTGetUs();// Get this time 
            flag = 1;
        }
        if (value == IOT_GPIO_VALUE0 && flag == 1) {
    // High level ends and becomes low level 
            time = IoTGetUs() - start_time;// Calculate the high level maintenance time 
            start_time = 0;
            break;
        }
    }
               /* =============== GPIO Communication mode process  4 Substitute the formula to calculate ======================================== */
    distance = time * 0.034 / 2;
    // printf("distance is %f\r\n",distance);
    return distance;
}

Print the results

About the other three modes of communication , Waiting for the author 10K o 0603 When the resistance arrives, I'm making an introduction .