MATLAB Rendition: XBee Test-Sketch

Hello!

A while ago, I created a post titled ‘XBee Test Sketch’. This was the premise:  you hit a key on keyboard and robot moves in the requested direction. From reading more recent posts, however, you’ll know I am working to set up the MATLAB <–> XBees <–> Robot interface(s); incorporating MATLAB is the next step after setting up the simple XBee <–> Robot interface, which is what the ‘XBee Test Sketch’ Post addressed.

(Scroll to bottom for final code).

Working Through It:

I started with these two lines:

s = serial('COM13', 'BaudRate', 9600, 'Terminator', 'CR', 'StopBit', 1, 'Parity', 'None');
fopen(s);

Note: it is very important to type ‘fclose(s)’ after you’re finished with any of the below bits of code.

And I was initially following that with code that looked like this:

while(1) 
fprintf(s, '//'); 
fscanf(s) 
s.BytesAvailable 
end

But I needed a loop that wouldn’t require quitting MATLAB everytime I wanted to change something… and didn’t really need MATLAB responding to XTCU, so I changed it to this:

for c = 1:10
fprintf(s, a)
end

—-

I wanted a simpler way to send commands to XTCU; it turns out you can just use:

fprintf(s, 'whatever you want to send');

The problem, however, was that I didn’t want to have to write ‘fprintf(s, ‘whatever’)’ every time I wanted to send a character. So I tried this:

a = 'hello'

for c = 1:10
pause(10)
fprintf(s, a)
end

I needed to specify ‘a’ ahead of the loop so that MATLAB would recognize it. But I then gave myself 10 seconds delay within the loop, thinking I could change ‘a’s value in that time, and MATLAB would send the new one.

It did not. It took like two whole minutes to get through all those ‘hello’s lol.

—-

I needed a better way for MATLAB to take/send the characters I wanted.

I tried the ‘MATLAB asks for user input’ method, but I still had to hit ‘Enter’ after every key stroke for the command to send to XTCU. Since the idea was for the input/robot-reaction to be continuous, like in ‘XBee Test Sketch’, this wasn’t the best option:

for c = 1:3
x = input('what would you like to send?','s')
fprintf(s, x)
end

The Solution:

I did some more Googling and found a MATLAB function called GetKey. Aptly named, it freezes MATLAB and intakes your next keystroke. Here’s the code I came up with:

(Because I programmed the letters (not ASCII values) ‘i’, ‘j’, ‘k’ and ‘l’ into the ‘XBee Test Sketch’ Arduino code, I used GetKey’s ‘non-ascii’ option).

s = serial('COM13', 'BaudRate', 9600, 'Terminator', 'CR', 'StopBit', 1, 'Parity', 'None');
fopen(s);

for c = 1:3
x = getkey('non-ascii')
fprintf(s, x)
end

The for-loop length can (and should be) adjusted depending. I put 1:100 to test it, and it worked great!

Here’s a video! (will download) 191019KA_MATLABtoRobot