How to make the time invtervals between two index fixed when plotting in real time using function 'tic toc'

Hi everyone,

I meet a problem when I'm trying to plotting some signals in real time from Arduino to Matltb. I use 'tic toc' to get elapsed time and it works. But when I look back to the 'time' output, the intervals between two neighouring index are irregular. But I want the time intervals to be fixed, for example, it recordes index every 0.3 seconds regularly. My code is look like below:

a = arduino()
%some other code here
tic
while ishandle(plotGraph1)
    count = count + 1;   
    time(count) = toc;
    %some other code here
end

I understand why that tic toc can lead to such irregular time intervals, so is there any other options I can use to represent the elapsed time with consistent increasement? Thanks a lot for your help!

Answer 1

[KALYAN ACHARJYA]

"But I want the time intervals to be fixed, for example, it recordes index every 0.3 seconds regularly. My code is look like below"

This way?

while condition
%record
pause(0.3)%
end

Tic ​​start is a stopwatch timer, it return time requiremnets for the code execution until toc. Exact Time: Please note, even in the given code, you must calibrate the fraction of tiny fraction of second required to run the loop (excluding pause).

[LuYao Guo]

Hi Sir, first of all, thank you for answering. I try the code 'pause', and it makes the intervals change less, although they are still not consistent. Could you please explain more about the 'calibration' please? Do I need to calibrate inside the while loop? BTW, in my while loop, I read and plot the data from Arduino, is it because this loop is complex that leads to the probleams of irregular time invertals? Just in case, I put the whole while loop here.

tic 
while ishandle(plotGraph1) 
        
         count = count + 1;   
         time(count) = toc;
         
         dat1 = readVoltage(a,'A2'); 
         dat2 = readVoltage(a,'A3'); 
         
         
         %moving average filter
         dat1_filtered = movmean(dat1,10);
         dat2_filtered = movmean(dat2,10);
         
         data1(count) = dat1_filtered(1);
         data2(count) = dat2_filtered(1);

         set(plotGraph1,'XData',time,'YData',data1);
         set(plotGraph2,'XData',time,'YData',data2);
        
         ylim('auto');
         axis([time(count)-10 time(count) min max]);
          %Update the graph
          %pause(delay);
          pause(0.33333);
end
  toc

Thank you very much.