I am currently working on a robotics project and it required a bit of quick testing. The quickest way to get a reading, other than the LCD was UART + a Matlab script. I wrote my own MATLAB script, but it required some obscure functions to get it working.
So I thought I’ll share the important tidbits.
The serial object
It’s kind of like the file pointer data structure in C. It will store the port info, but you’ll have to use fopen, fgets and fclose like manipulating files in C. Actually, the port data has been abstracted to the file. However, fclose is a big deal if you want other programs (such as a code uploader) to access your port.
s = serial('COM3') % COM3 is a port. Put whatever port your connected to!
set(s,'BaudRate', 115200); %Set your baud rate!
s.InputBufferSize = 5000; %Set the input buffer size (how much data can be stored)
fopen(s);
... %Other code omitted
while(1) %Infinite loop!
if s.BytesAvailable > 0 % To avoid timeout and other weird things
str = fgets(s);
...
end
end
fclose(s); %Now you can access the object
Exception/Error handling
You’ll need this part because you want to close your port and let other programs access it in case something bad happens.
try
... %Your code here
catch err %Catch the damn problem
fclose(s);
end;
Plotting
Here you can plot as usual as except you’ll have to use drawnow to plot your data immediately and hold on if you’re going to add data to the existing plot.
figure(1);
hold on;
...
while(1)
...
plot(A);
drawnow;
end
String manipulation
Here I’ve used sscanf to manipulate the string. I think there is also a direct function to get both getting a line and scanning done at the same time. You can look up the usage easily. The code basically returns a column vector according to the format specified using C’s format specifiers (but look it up, to make sure!).
My data was of a white line sensor and I was getting it’s left, middle and right values hence the L:%d M:%d R:%d.
A = sscanf(str, 'L:%d M:%d R:%d');
All the code
Here it is, in all it’s glory:
clear all;
close all;
figure(1);
delay = 0.5;
s = serial('COM3');
set(s,'BaudRate', 115200);
s.InputBufferSize = 5000;
fopen(s);
input('Ready?');
try
A = [0;0;0];
while(1)
if s.BytesAvailable > 0
str = fgets(s);
A = sscanf(str, 'L:%d M:%d R:%d');
bar(A)
axis([0 4 0 255]);
drawnow
A = [0;0;0];
end
end;
fclose(s);
catch err
fclose(s);
end;