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

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%% 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

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Accepted Answer

Walter Roberson
Walter Roberson on 21 Jan 2021
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.

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WAN NOR NAZIRA MUSTAPA KAMAL
before I start again, I clear the workspace and command window. then I run the program again
Walter Roberson
Walter Roberson on 22 Jan 2021
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.

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