How can I call a function for a specific amount of time, using a Timer function?

I'm currently working on a serial port communications function, wherein I take multicolumn data from the serial port (from an Arduino, via Bluetooth), for saving the sensor data stream into a database, for later work with Machine Learning and curve fitting algorithms. Currently, I am facing the issue where I'm controlling the flow of data from Arduino to Matlab by sending either a '1' (enable transmission) or '0' (Stop Transmission). I want to ensure that whenever I send a 1 (by calling a separate function sendval), it runs for 5 seconds, and then sends a 0,so that the data stream captured during that period is being saved into a database on MATLAB.

At the moment, I'm having no problem sending a '1' and saving the incoming data, except that I'm only getting ONE instance of the sensor readings, rather than a repeating stream. How do I call the same function repeatedly for, say, 5 seconds? (I can include a pause of 0.1 seconds in the function to get the readings at intervals of 0.1 seconds). This is my current code:

     function bttest()
  % This function sends a 1 and 0 alternately to the Bluetooth module, trying
  % to fetch random numbers generated on an Arduino
  % The base Arduino Sketch (later modified to transmit random numbers, rather than digitalWrite for LEDs) is given at:
  % http://www.instructables.com/id/Arduino-AND-Bluetooth-HC-05-Connecting-easily/
  clear;clc;
  b=Bluetooth('HC-05',1);
  fopen(b);
  for(i=1:10) % Repeat for 10 sets of samples
  pause(2);   % Two second delay initially
  sendval(1);     % Initiate serial data reception
  pause(5);       %Run for 5 seconds
  sendval(0);     %Stop serial data reception
  pause(5);
  end

function sendval(val)
fprintf(b,'%u',val);
    % while(val = 1)
    m = fscanf(b);
    pause(0.1);
   end
end

Any help or suggestions would be greatly appreciated. I'm not very familiar with the Timer function, but if anyone could help me figure out how to use a timer function to call that sendval function repeatedly for 5 seconds at 0.1 sec intervals, I'd be thankful.

Thank you in advance!

Answer 1

[Chad Greene]

The sendval function has no outputs. Perhaps you want the first line of sendval to be

function m = sendval(val)

which will return whatever is the output of fscanf(b).

Another problem: When you call

sendval(1);     % Initiate serial data reception
pause(5);       %Run for 5 seconds

it does not run sendval for 5 seconds. Rather, it runs sendval for however long sendval takes (I think the way you've written it, it will take roughly 0.1 seconds). Consider rewriting sendval with a second input where you can specify how long sendval will run. For example:

function m = sendval(val,RunFor)

% Start a timer: 
tic       

% Do this loop over and over until the timer reaches RunFor seconds:  
while toc<RunFor 
   fprintf(b,'%u',val);
   m = fscanf(b);
   pause(0.1);
end

end

To illustrate the while loop with tic and toc run this by itself:

RunFor = 3; 

% Start a timer: 
tic       

% Do this loop over and over until the timer reaches RunFor seconds:  
while toc<RunFor 
   disp(['It has been ',num2str(toc),' seconds.'])
   pause(0.1);
end

[Ravikiran B A]

Thank you very much! I have used tic-toc before for timing my scripts, but I hadn't thought about using them as a timer.

I went ahead and removed the function (It was just displaying the values, rather than saving them in an array). Then, I just took the fscanf command and put it in the tic-toc timer loop, did a bit of debugging, and was finally able to load the data into an array.

Thank you very much!

[Chad Greene]

Great, glad I could help.