USB serial data receive problem and 'COM' port problem?

I have written following code to receive serial data and move cube. But I am not receiving data in MATLAB command window as well cube not rotating. I checked in terminal software about data receive, and hardware worksfine. Please correct my code.

    A1 = 0; B1 = 0; C1 = 0; 
   A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
pause
s = serial('COM6');
fopen(s)
for i = 1:1000
   P = fgets(s)

 if P == '5'
       A1 = 0; B1 = 0; C1 = 0; 
   A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
   grid on
 elseif P == '1'

   A1 = A1+1; B1 = B1; C1 = C1; 
   A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
   grid on
 elseif P == '2'

    A1 = A1-1; B1 = B1; C1 = C1; 
 A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
   grid on
 elseif P == '3'

    A1 = A1; B1 = B1; C1 = C1+1; 
 A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
   grid on
 elseif P == '4'

    A1 = A1; B1 = B1; C1 = C1-1; 
   A = [A1 B1 C1];
   B = [A1+1 B1 C1];
   C = [A1 B1+1 C1];
   D = [A1 B1 C1+1];
   E = [A1 B1+1 C1+1];
   F = [A1+1 B1 C1+1];
   G = [A1+1 B1+1 C1];
   H = [A1+1 B1+1 C1+1];
   P = [A;B;F;H;G;C;A;D;E;H;F;D;E;C;G;B];
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3),'g'), hold on
   roll = 2*pi; pitch = 2*pi; yaw = 2*pi;
   dcm = angle2dcm(yaw, pitch, roll);
   P = P*dcm;
   axis([-25 25 -25 25 -25 25])
   plot3(P(:,1),P(:,2),P(:,3)) % rotated cube
   axis([-25 25 -25 25 -25 25])
   plot3(0,0,0,'or')
   xlabel('X')
   ylabel('Y')
   zlabel('Z')
   grid on
 else 
 end
 end
 fclose(s)
 delete(instrfindall)

Answer 1

[Walter Roberson]

fgets() always returns the line with the line terminator included. You then compare the line to a single character. The line terminator is not going to match the character so the comparison will always be false.

I always recommend using fgetl() instead of fgets() except under uncommon circumstances. And if you are reading a single character, use fread() with a count of 1.

[Nimisha]

I just replaced fgets by fgetl and getting following results, and cube not able to move.

 Warning: Unexpected Warning: A timeout occurred before the Terminator was reached. 

 P =

 1
 4
 2

Getting this data occasionally and simultaneously.There is no smooth moving of cube.

[Nimisha]

please help as soon as possible.!

[Walter Roberson]

For the moment, for testing purposes, switch back to fgets(), but after you read the value, display double(P) and tell us what the values look like.

You should also be switching to use strcmp() instead of using == for strings.

I did not compare line for line, but it looks to me as if your different cases involve one different line such as

   A1 = A1; B1 = B1; C1 = C1-1;

and that the rest of the drawing code is the same? If so then it would be more readable to have the if block only set the A1, B1, C1 as appropriate, and then after the end of the if, have the common drawing code.