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

Question

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

Answer 1

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.