App Designer not identifying 'readVoltage'

I had made a callback for a button in App Designer that when pushed would read voltages from an arduino 'A0' pin and it was wokring. Suddenly when I tried to run the app again I was getting an error of "Undefined function 'readVoltage' for input arguments of type 'double'". I had not changed the code in between this happening but now I cannot fix it.

function ButtonPushed(app, event)
    clc
    global b
    x1=0;
    
    global go
    go=true;
    
    while go
        tempA1 = readVoltage(b, 'A0');
        tempA2 = 32+(9/5)*(tempA1*100);
        x1=[x1 tempA2];
        plot(app.UIAxes,x1);
        drawnow
        pause(1);
    end
end

Answer 1

[Ameer Hamza]

You have used 'b' as a global variable. In the base workspace, you need to define it as an Arduino object

b = arduino;

If it has some other type, you will get this error

[Michael Pineda]

I do have 'b' as a an Arduino object. The libaries i have on it are 'I2C' 'SPI' and 'Servo' could I be missing one?

[Michael Pineda]

I can read the voltages of each pin when i type readVoltage(b,'A0') in the command window perfectly. I only get this error in AppDesigner

[Ameer Hamza]

Have you typed global b in command window?

[Michael Pineda]

Yes I did and the error continues to be displayed

Answer 2

[Fazli Wadood]

I have use this its working.

clc

global b

b = arduino;

x1=0;

global go

go=true;

while go

tempA1 = readVoltage(b, 'A0');

tempA2 = 32+(9/5)*(tempA1*100);

x1=[x1 tempA2];

plot(app.UIAxes,x1);

drawnow

pause(1);

end