I am measuring voltage from a pot on my Arduino Uno. My time vector grows but all the index values of my voltage vector are the same as I vary the pot.

I need to store the individual voltage values as I vary the pot. I included the file, any help is appreciated.

Answer 1

[Ameer Hamza]

I could not understand the reason for using a for loop inside the while loop. Try the following code. I have also made some other changes e.g. you were calling plot() inside while loop which can make the code slow. I have used figure handle to update the same figure.

%Use a flag so that you can "append" new data to the end of it
time=0;
t=[];   % although pre-allocation is good, but the number of samples are not known in advance.
      % If your data size is small, it will not matter much.
voltage=[];

f = gcf; % instead of creating new axis inside the while loop. Create a figure, and update its handle
ax = gca;
l = line();
l.XData = [];
l.YData = []
ylim([0 5]);
xlabel('time (s)');
ylabel('voltage (v)');
title('analog data from the potentiometer');
while (flag==0)
  t=[t time];
  time=time+1;
  voltage = [voltage readVoltage(a,pot)];   
  if (readDigitalPin(a,button)==1) %button is pressed
      break; % nor need for flag, just break the loop
  end
  c=clock;
  fprintf(fid,'%4.0d %2.0d %2.0d %2.0d %2.0d %6.4d %d\n',c,sin(c(6)));
  pause(1);
  % Plot the data
  l.XData = t;
  l.YData = voltage;
end

Also, you are not writing the voltage value in the file, you might want to look into that.

[Alan Clemenson]

I dont understand the first five lines beginning at f=gcf. I'm still very new to Matlab. I had the plot inside the loop temporarily so I could troubleshoot and see whats happening to the data, so it isn't really needed. I don't know how to amend my code to write voltage to the time stamped file and help with that would be much appreciated as well. I will look up the functions you provided and try to understand. Thank you for your help so far.

[Alan Clemenson]

Ok, those commands are actually relatively straight forward. Thank you very much. I just need to figure out how to write my voltage into the time stamp.

[Ameer Hamza]

I think there is no point in writing sin(c(6)) to the file. You can write the voltages like this

fprintf(fid,'%4.0d %2.0d %2.0d %2.0d %2.0d %6.4d %d\n',c, voltage(end));

[Alan Clemenson]

Thank you, I'm pretty excited about being able to recall and update a figure this way too. That's everything.

[Ameer Hamza]

You are welcome.