Real Time MULTIPLE Plot Data Accelerometer STM32 F4 Discovery

Dear all,

my name is FIlippo from Bologna, Italy. I am using the STM32 F4 Discovery microcontroller that has a built-in accelerometer. I am streaming the three acceleration values through the serial port (Via USART) in this format: Value_x,Value_y,Value_z . I would like to stream these datas in a Matlab plot that refreshes continuosly. I made some researches on the web, and I found out a code that works well. I modified a little bit it. The problem is that this code allows to stream only ONE data (in my case, only one axis). As you can see, in the variable dat = fscanf(s,['%d,%d,%d']); i can correctly read all three acceleration, but actually i do not now how to plot three values instead of only one.

I just need three run-time plot, every form of plot is good: 3xsubplots, 3x different figure, 1 plot with three lines...everything will be ok.

Thank you very much.

Best regards Filippo

   clear
   clc

   %User Defined Properties 
   serialPort = 'COM9';            % define COM port #
   plotTitle = 'Serial Data Log';  % plot title
   xLabel = 'Elapsed Time (s)';    % x-axis label
   yLabel = 'Data';                % y-axis label
   plotGrid = 'on';                % 'off' to turn off grid
   min = -2010;                     % set y-min
   max = 2010;                      % set y-max
   scrollWidth = 10;               % display period in plot, plot entire data log if <= 0
   delay = .01;                    % make sure sample faster than resolution

   %Define Function Variables
   time = 0;
   data_x = 0;
   count = 0;

   %Set up Plot
   plotGraphx = plot(time,data_x,'-mo',...
                'LineWidth',1,...
                'MarkerEdgeColor','k',...
                'MarkerFaceColor',[.49 1 .63],...
                'MarkerSize',2);

   title(plotTitle,'FontSize',25);
   xlabel(xLabel,'FontSize',15);
   ylabel(yLabel,'FontSize',15);
   axis([0 10 min max]);
   grid(plotGrid);

   %Open Serial COM Port
   s = serial(serialPort)
   disp('Close Plot to End Session');
   fopen(s);

   tic 

   while ( ishandle(plotGraphx)  ) %Loop when Plot is Active && ishandle(plotGraphy) && ishandle(plotGraphz)

       dat = fscanf(s,['%d,%d,%d']); %Read Data from Serial as Float: PLEASE NOTE: Here i modified the code, in order to adjust the correct format of data in input.

       if(~isempty(dat) && isfloat(dat)) %Make sure Data Type is Correct        
           count = count + 1;    
           time(count) = toc;    %Extract Elapsed Time
           data_x(count) = dat(1); %Extract 1st Data Element   

           %Set Axis according to Scroll Width
           if(scrollWidth > 0)
           set(plotGraphx,'XData',time(time > time(count)-scrollWidth),'YData',data_x(time > time(count)-scrollWidth));
           axis([time(count)-scrollWidth time(count) min max]);
           else
           set(plotGraphx,'XData',time,'YData',data_x);
           axis([0 time(count) min max]);
           end

           %Allow MATLAB to Update Plot
           pause(delay);
       end
   end

   %Close Serial COM Port and Delete useless Variables
   fclose(s);
   clear count dat delay max min plotGraph plotGrid plotTitle s ...
           scrollWidth serialPort xLabel yLabel;

   disp('Session Terminated...');

[Mansi Gupta]

U ended the code with two ends, is it necessary to end communication when we are uploading the program to Arduino or other microcontroller.

Answer 1

[Ameer Hamza]

Refer to my answer here, which deals with exactly the same problem. The main point is, you can have several lines on a single axis and obtain their handles. Then you add data to those handles in a similar way as you are doing now. Here is a general sketch of what you need to do

plotGraphx = plot(time,data_x,'-mo',...
              'LineWidth',1,...
              'MarkerEdgeColor','k',...
              'MarkerFaceColor',[.49 1 .63],...
              'MarkerSize',2);
hold on;  % it will hold all the lines on same axis
plotGraphy = plot(time,data_y,'-mo',...   <---- define data_y before this
              'LineWidth',1,...
              'MarkerEdgeColor','k',...
              'MarkerFaceColor',[.49 1 .63],...
              'MarkerSize',2);
plotGraphz = plot(time,data_x,'-mo',...
              'LineWidth',1,...
              'MarkerEdgeColor','k',...
              'MarkerFaceColor',[.49 1 .63],...
              'MarkerSize',2);

Then in the while loop, do something like this

data_x(count) = dat(1);  
data_y(count) = dat(2); 
data_x(count) = dat(3);

and for adding the points, use the respective handles

set(plotGraphx,'XData',time(time > time(count)-scrollWidth),'YData',data_x(time > time(count)-scrollWidth));
set(plotGraphy,'XData',time(time > time(count)-scrollWidth),'YData',data_y(time > time(count)-scrollWidth));
set(plotGraphz,'XData',time(time > time(count)-scrollWidth),'YData',data_z(time > time(count)-scrollWidth));

similar for the else statements.

[Filippo Marinelli]

Thank you really much, everything now works perfectly. I did not create 3x different plots...this was my mistake. I share the code below, maybe it could help someone.

Best regards Filippo clear clc

   %User Defined Properties
   serialPort = 'COM3';            % define COM port #
   plotTitle = 'Serial Data Log';  % plot title
   xLabel = 'Elapsed Time (s)';    % x-axis label
   yLabel = 'Data';                % y-axis label
   plotGrid = 'on';                % 'off' to turn off grid
   min = -2010;                     % set y-min
   max = 2010;                      % set y-max
   scrollWidth = 10;               % display period in plot, plot entire data log if <= 0
   delay = .01;                    % make sure sample faster than resolution

   %Define Function Variables
   time = 0;
   data_x = 0;
   data_y = 0;
   data_z = 0;

   count = 0;

   %Set up Plot
   plotGraphx = plot(time,data_x,'-mo',...
       'LineWidth',1,...
       'MarkerEdgeColor','k',...
       'MarkerFaceColor',[.49 1 .63],...
       'MarkerSize',2);
   hold on;  % it will hold all the lines on same axis

   plotGraphy = plot(time,data_y,'-mo',...   <---- define data_y before this
       'LineWidth',1,...
       'MarkerEdgeColor','k',...
       'MarkerFaceColor',[.49 1 .63],...
       'MarkerSize',2);
   plotGraphz = plot(time,data_z,'-mo',...
       'LineWidth',1,...
       'MarkerEdgeColor','k',...
       'MarkerFaceColor',[.49 1 .63],...
       'MarkerSize',2);

   title(plotTitle,'FontSize',25);
   xlabel(xLabel,'FontSize',15);
   ylabel(yLabel,'FontSize',15);
   axis([0 10 min max]);
   grid(plotGrid);

   %Open Serial COM Port
   s = serial(serialPort)
   disp('Close Plot to End Session');
   fopen(s);

   tic

   while ( ishandle(plotGraphx)  ) %Loop when Plot is Active && ishandle(plotGraphy) && ishandle(plotGraphz)

       dat = fscanf(s,['%d,%d,%d']); %Read Data from Serial as Float: PLEASE NOTE: Here i modified the code, in order to adjust the correct format of data in input.

       if(~isempty(dat) && isfloat(dat)) %Make sure Data Type is Correct
           count = count + 1;
           time(count) = toc;    %Extract Elapsed Time
           data_x(count) = dat(1);
           data_y(count) = dat(2);
           data_z(count) = dat(3);

           %Set Axis according to Scroll Width
           if(scrollWidth > 0)
               set(plotGraphx,'XData',time(time > time(count)-scrollWidth),'YData',data_x(time > time(count)-scrollWidth));
                set(plotGraphy,'XData',time(time > time(count)-scrollWidth),'YData',data_y(time > time(count)-scrollWidth));
               set(plotGraphz,'XData',time(time > time(count)-scrollWidth),'YData',data_z(time > time(count)-scrollWidth));
               axis([time(count)-scrollWidth time(count) min max]);
           else
               set(plotGraphx,'XData',time,'YData',data_x);
               set(plotGraphy,'XData',time,'YData',data_y);
               set(plotGraphz,'XData',time,'YData',data_z);
               axis([0 time(count) min max]);
           end

           %Allow MATLAB to Update Plot
           pause(delay);
       end
   end

   %Close Serial COM Port and Delete useless Variables
   fclose(s);
   clear count dat delay max min plotGraph plotGrid plotTitle s ...
       scrollWidth serialPort xLabel yLabel;

   disp('Session Terminated...');

[Ameer Hamza]

You are welcome.

[ASHISHREDDY THUMMALA]

hello Ameera Hamza,

Im doing the similar work, the output I am geeting is in the format

Value_x Value_y Value_z(without commas)

" " " " " "

continously,

i have tried using your code, please suggest me in this .

[karthiknatarajan baskaran]

please give me example arduino code..

[Francesco Lucarelli]

Hi all,

i would like to read continuos data from an accelerometer.Before i was using hterm but it does not support long recording.

I was wondering if i can do that with matlab

My port is COM15 with a baud 8200000, it should create a new line every 13 characters (i have 1 byte to identy the accelerometer, 4 for time, 2 for x 2 for y 2 for z 2 for the current)

Can anyone help me with this?