Hi all! Could you please help me understand this piece of code here?

%% setup

hold all

a = arduino('COM3', 'Uno');

mpu = i2cdev(a,'0x68'); %mpu adress is normally 0x68

writeRegister(mpu, hex2dec('B6'), hex2dec('00'), 'int16'); %reset

data = zeros(10000,14,'int8'); %prelocating for the speed

j = 1;

a1 = animatedline('Color',[1 0 0]);

a2 = animatedline('Color',[0 1 0]);

a3 = animatedline('Color',[0 0 1]);

legend('Accel_x','Accel_y','Accel_z')

%% loop

while(true)

x=1;

for i=59:72 % 14 Data Registers for Accel,Temp,Gyro

data(j,x) = readRegister(mpu, i, 'int8');

x = x + 1;

end

y = swapbytes(typecast(data(j,:), 'int16')) %if your system is big-endian remove the swapbytes function

addpoints(a1,j,double(y(1)));

addpoints(a2,j,double(y(2)));

addpoints(a3,j,double(y(3)));

j = j+1;

drawnow limitrate

end

Answer 1

[Walter Roberson]

It initializes an i2c register on the arduino. It loops indefinitely. Each cycle it reads 14 bytes of data that are in big-Endian order. It rearranges the data to be 16 bit little-Endian signed 16 bit integers. It takes the first three of those and adds them to the plot and ignores the rest.

After 10000 points it will slow down a lot for memory allocation reasons.

The code could be trimmed a bit, such as not reading the values it is not going to use.

[WAN NOR NAZIRA MUSTAPA KAMAL]

For the last part of your answer, can you explain more? can you give an example? actually, I am having problem with the code where when I first run the code, the outcome that I get is data in values and graph but when I want to re run the code for the second time and so on, the outcome that I get is zero data values and the graph is in straight line. Is there any problem with the code? Could you help me?

[Walter Roberson]

Trimming:

data = zeros(10000,6,'int8'); %prelocating for the speed

for i=59:64 % 6 Data Registers for Accel

[WAN NOR NAZIRA MUSTAPA KAMAL]

It still the same. The data of outcome is zero in 3 matrix vector and the graph is in straight line.

[Walter Roberson]

How are you terminating the run when you stop it the first time? Do you do anything particular before you run again, or do you just start the program again?

[WAN NOR NAZIRA MUSTAPA KAMAL]

before I start again, I clear the workspace and command window. then I run the program again

[Walter Roberson]

You are control-c or clicking the Pause button in the editor? I am concerned that the arduino connection might still be open.

[WAN NOR NAZIRA MUSTAPA KAMAL]

I am clicking the Pause button in the editor. I clear the command window and workspace the run again.