replicating Arduino pulseIn() on Matlab

Long story short I have to replicate the Arduino pulseIn() command in MatLAB reading in an acceleration X and Y component. I was doing research and found that this link:

https://www.mathworks.com/matlabcentral/answers/33710-how-to-replicate-an-arduino-timer-function-in-matlab

had a similar request but the "adiosrv.pde" file is outdated and the native command (tic, toc) for Matlab is not consistent enough to give me the accurate readings I need for this project. Apparently the .pde file has changed name and/or been split up into multiple documents and I cannot find it anywhere for the life of me. any input?

Answer 1

[Nagarjuna Manchineni]

I see that the solution in the link that you are referring was written for Giampiy's legacy Arduino library, which I think was the case with the pde file. It is not applicable now.

To measure distance using the new Arduino object, there is an Ultrasonic Sensor add-on library on matlabcentral, but you need to first install a 3rd party library as explained in the instructions on that page.

https://www.mathworks.com/matlabcentral/fileexchange/57898-hc-sr04-add-on-library-for-arduino

If this Add-on does not work with your Ultrasonic Sensor, you can use it as a template to create your own custom add-on library.

Here's the doc for creating custom add-on libraries for Arduino.

https://www.mathworks.com/help/supportpkg/arduinoio/ug/custom-library-concepts.html

I hope this helps!

[Welid Benchouche]

Hi sir, i am trying to run my ultrasonic sensor with the Raspberry pi 3 model B board, i tried mimicing the code from python but it doesnt work , it keeps increamenting nonstop.here is my code for it

clc;
a = raspi;
trig = 26; % gpio 26
echo = 16; % gpio 16
global x y 
x = 0; y = 0;
configurePin(a, trig,'DigitalOutput')
configurePin(a, echo,'digitalinput')
pause(3)
disp('starting')
writeDigitalPin(a,trig,1)
disp('trig is on')
pause(0.00001)
writeDigitalPin(a,trig,0)
while 1
while readDigitalPin(a,echo) == 0
    tic; x = toc;
    break;
end
while readDigitalPin(a,echo) == 1
    y = toc;
    break;
end
dur = -(y-x)
distance = dur * 17150

% dur = y-x;
% distance = dur * 17000;
% distance = round(distance, 3);
% sprintf('Distance : %f cm',distance)
% % writeDigitalPin(a,trig,0)
% %     while true
% %         writeDigitalPin(a,trig,0)
% %         pause(0.1)
% %         writeDigitalPin(a,trig,1)
% %         pause(0.001)
% %         writeDigitalPin(a,trig,0)
% %         while readDigitalPin(a,echo) == 0 
% %             tic;pulse_start = toc;
% %         end
% %         while readDigitalPin(a,echo) == 1 
% %             pulse_end = toc;
% %             return
% %         end
% %     end
% % pulse_duration = pulse_end - pulse_start
% % distance = pulse_duration * 17000
% % if pulse_duration >=0.01746
% % disp('time out')
% % 
% % elseif distance > 300 && distance==0
% % disp('out of range')
% % end
% % distance = round(distance, 3);
% % sprintf('Distance : %f cm',distance)
% % 
%  clear x y distance ans dur 
 end

[Walter Roberson]

tic; x = toc;

I am unclear as to the reason for that?

while readDigitalPin(a,echo) == 0
    tic; x = toc;
    break;
end

Especially since you "break" as soon as the condition is met.

x = toc at that point would only measure the time since the tic that is in the same line, which should be a fairly minor amount of time; I don't think your code is really intended to measure MATLAB internal efficiency there ??

[Welid Benchouche]

could you please tell me how to convert this python code to matlab ? because this is my problem

don't worry about the GPIO. .. stuff, i just need to calculate the time

def distance():
    # set Trigger to HIGH
    GPIO.output(GPIO_TRIGGER, True)
 
    # set Trigger after 0.01ms to LOW
    time.sleep(0.00001)
    GPIO.output(GPIO_TRIGGER, False)
 
    StartTime = time.time()
    StopTime = time.time()
 
    # save StartTime
    while GPIO.input(GPIO_ECHO) == 0:
        StartTime = time.time()
 
    # save time of arrival
    while GPIO.input(GPIO_ECHO) == 1:
        StopTime = time.time()
 
    # time difference between start and arrival
    TimeElapsed = StopTime - StartTime
    # multiply with the sonic speed (34300 cm/s)
    # and divide by 2, because there and back
    distance = (TimeElapsed * 34300) / 2
 
    return distance

[Walter Roberson]

a = raspi;
trig = 26; % gpio 26
echo = 16; % gpio 16

configurePin(a, trig,'DigitalOutput')
configurePin(a, echo,'digitalinput')
pause(3)
disp('starting')

writeDigitalPin(a,trig,1)
disp('trig is on')
pause(0.00001)
writeDigitalPin(a,trig,0)

while 1
    StartTime = tic;
    while readDigitalPin(a,echo) == 0
        StartTime = tic;
    end
    StopTime = toc;
    while readDigitalPin(a,echo) == 1
        StopTime = tic;
    end
    TimeElapsed = StopTime - Starttime;
    distance = dur * 17150;
    %at this point do something with distance
end

But this could also be written as

a = raspi;
trig = 26; % gpio 26
echo = 16; % gpio 16

configurePin(a, trig,'DigitalOutput')
configurePin(a, echo,'digitalinput')
pause(3)
disp('starting')

writeDigitalPin(a,trig,1)
disp('trig is on')
pause(0.00001)
writeDigitalPin(a,trig,0)

while 1
    while readDigitalPin(a,echo) == 0
        %do nothing -- that is, loop until it reads differently
    end
    StartTime = tic;
  
    while readDigitalPin(a,echo) == 1
         %do nothing -- that is, loop until it reads differently
    end
    StopTime = toc;
    
    TimeElapsed = StopTime - Starttime;
    distance = dur * 17150;
    %at this point do something with distance
end

[Welid Benchouche]

Dear @Walter Roberson

Both codes won't work, because the code is stuck in this loop and never passes it

    while readDigitalPin(a,echo) == 0
        %do nothing -- that is, loop until it reads differently
    end

it never detects when the echo pin goes high for some reason.

[Walter Roberson]

It would be interesting to instead use

maxtry = 25;
got_one = false;
for trynum = 1 : maxtry
        value = readDigitalPin(a,echo);
        if value ~= 0; got_one = true; break; end
        disp('pin was 0')
end
if ~got_one
   error('No 0 found in %d tries', maxtry);
end