Warning: A Timeout Occurred Before Terminator Was Reached + Significant Time Delay

Hey All,

I am plotting data obtained from an accelerometer (ADXL345) through serial port from an Arduino uno. I have two questions:

1) When the code fails to work, the aforementioned error appears, preventing me from plotting the results.

I looked at similar threads, but I was unable to resolve the issue - I'm hoping if I provide some more details specific to my situation, someone may be able to help me.

2) When the code does work, the plot has a significant time delay - how can I make my code as efficient as possible?

Thanks for your help!

Here's the code:

%%Plots data from serial port in real time

% variables
time = 0;
data1 = 0;
data2 = 0;
data3 = 0;
index = 0;
scrollWidth = 10;
delay = 0.005;
min = -100;
max = 100;

graph1 = plot(time, data1, 'm-');
hold on;
graph2 = plot(time, data2, 'c-');
hold on;
graph3 = plot(time, data3, 'g-');

% setup serial port

s = serial('/dev/tty.usbmodem1411');
set(s, 'InputBufferSize', 1024);
set(s, 'FlowControl', 'hardware');
set(s, 'BaudRate', 115200);
set(s, 'Parity', 'none');
set(s, 'DataBits', 8);
set(s, 'StopBit', 1);
set(s, 'Timeout', 10);

fopen(s);

% start time
tic; 

while ishandle(graph1)

      stream = fscanf(s, '%f %f %f')';

      if(~isempty(stream))
          index = index + 1;
          time(index) = toc;

          if (numel(stream) < 3)
             continue;
          else
              data1(index) = stream(1, 1);
              data2(index) = stream(1, 2);
              data3(index) = stream(1, 3);
          end

          if(scrollWidth > 0)
              set(graph1,'XData', time(time > time(index) - scrollWidth), 'YData', data1(time > time(index) - scrollWidth));
              set(graph2,'XData', time(time > time(index) - scrollWidth), 'YData', data2(time > time(index) - scrollWidth));
              set(graph3,'XData', time(time > time(index) - scrollWidth), 'YData', data3(time > time(index) - scrollWidth));
              axis([time(index) - scrollWidth time(index) min max]);
          else
              set(graph1,'XData', time, 'YData', data1);
              set(graph2, 'XData', time, 'YData', data2);
              set(graph3, 'Xdata', time, 'YData', data3);
              axis([0 time(index) min max]);
          end
          pause(delay);
      end
  end

fclose(s);
delete(s);

Answer 1

[Walter Roberson]

One bit of improvement is

selidx = time > time(index) - scrollWidth);
xtime = time(selidx);
set(graph1, 'XData', xtime, 'YData', data1(selidx));
set(graph2, 'XData', xtime, 'YData', data2(selidx));

and so on.

You might also want to change the pause(delay) to drawnow()

You should also be considering whether you really need to update the graph after every line that is successfully read in. The less often you update the graph, the more efficient the drawing will be. Well, up to 10000 points or so at least.