I am using HC-SR04 ultrasonic sensor with raspberry pi 3 interfaced with MATLAB 2017b. When I run my code to measure distance of an object from sensor my code goes in infinite loop detecting nothing. Code is as follows:

 trig=17;
 echo=27;

 configurePin(mypi,echo,'DigitalInput')
 configurePin(mypi,trig,'DigitalOutput')

    writeDigitalPin(mypi,trig,0)
    pause(1)

    writeDigitalPin(mypi,trig,1)
    pause(0.00001)
    writeDigitalPin(mypi,trig,0)

    readDigitalPin(mypi,echo)
    while readDigitalPin(mypi,echo)== 0
    a = toc

    while readDigitalPin(mypi,echo)== 1
    b = toc;
    end
    end

    pulseDuration = b-a;

    distance = pulseDuration*17150;
    distance= round(distance,2)

    display(distance)

[David-Gabriel Verrette]

I have the exact same issue with a similar code. Have you been able to solve the issue ?

[Sinan Çolak]

could you solve the error??

[松繁]

两个循环嵌套了，不应该这样写，这样肯定出不了循环

Answer 1

[松繁]

% clear mypi

% mypi=raspi;

configurePin(mypi,4,'DigitalOutput'); % 5脚设置为输出脚 21 Trig发送引脚

configurePin(mypi,17,'DigitalInput'); % 13脚设置为输入脚23 Echo接收引脚

%disp(readDigitalPin(mypi,17));

while (1)

dis=0;

try

dis=distance(mypi);

catch error % 捕获到异常

pause(2);

% disp("超出量程(4米)");

continue; % 跳出本次循环

end

pause(2);

if (dis>4) % 异常数据

pause(2);

% disp("超出量程(4米)");

continue; % 跳出本次循环

end

disp(dis+"米");

end

%编写测距函数并调用

function distance=distance(mypi)

while(readDigitalPin(mypi,17)==0)% 假如13脚一直为低电平，则一直循环

writeDigitalPin(mypi,4,0);

pause(0.5);

writeDigitalPin(mypi, 4, 1); % trig输出正向脉冲

pause(0.00001); % 10US=1.0e-5# pause(0.0001); % 100微妙 原//pause(n秒)

% pause(0.000012)= pause(1.2e-5) 保持10us以上（选择12us）

writeDigitalPin(mypi, 4, 0); % trig低电平

%pause(2.0e-4);%8个40kHz的TTL

disp("Echo脚低电平"); % 调试控制台打印数据

end

tic; % Echo脚变高电平时开始本次计时

while(readDigitalPin(mypi,17)==1)% 假如13脚一直为高电平，则一直循环

%disp("Echo高电平"); % 可能为HCSR04模块内部短路

end

distance=toc*343/2; % Echo脚变高电平时结束本次计时

% 中间时段便是HCSR04模块一次超声波传播并返回的总时间

end % 距离=时间*声速/2