Press a Button move a Servo

I am try to do the following:

When a button is pressed, the arm on a servo will go from 0 degrees to 90 degrees, wait 30 seconds, then return to 0.

I am SO lost.

Here is what I have so far.:

I cannot figure out what to write for moving the arm of the servo.

clear s %clear the servo object if used previously
s = servo(a, 'D9', 'MinPulseDuration', 400*10^-6, 'MaxPulseDuration', 2100*10^-6)

%Define cell array variable for key pins and configure with built-in pullup resistors
keyPins = {'D2','D3'};

configurePin(a,keyPins{1},'pullup');

%set the position to 0
writePosition(s, 0);
pause(2) %wait 2 seconds

%Open or close the Chest Depending on Button Press
%While loop runs commands inside as long as the condition in parentheses evaluates to true.
while(1) %Condition in parentheses is always true
    %read states of key pins into vector
    keyStates(1) = readDigitalPin(a,keyPins{1});
    keyStates(2) = readDigitalPin(a,keyPins{2});
    
if keyStates == [1]  %true if the first key is pressed
        % Code goes here to move the arm from 0 to 90 when button is
        % pressed
        
end
end

Answer 1

[Shreshth]

Hey Ravyn,

After analysing the code provided by you to control a servo motor using MATLAB code while interfacing with the Arduino Uno, I could see that the code is missing the part where the servo arm needs a command for movement when the button is pressed.

Here is the corrected code snippet:

clear s %clear the servo object if used previously
s = servo(a, 'D9', 'MinPulseDuration', 400*10^-6, 'MaxPulseDuration', 2100*10^-6)
% Define cell array variable for key pins and configure with built-in pullup resistors
keyPins = {'D2','D3'};
configurePin(a,keyPins{1},'pullup');
% Set the position to 0
writePosition(s, 0);
pause(2) % Wait 2 seconds
 
% While loop runs commands inside as long as the condition in parentheses evaluates to true.
while(1) % Condition in parentheses is always true
    % Read states of key pins into vector
    keyStates(1) = readDigitalPin(a,keyPins{1});
    keyStates(2) = readDigitalPin(a,keyPins{2});
    
    if keyStates(1) == 0  % True if the first key is pressed (pullup resistor makes default state HIGH)
        % Move the arm from 0 to 90 degrees
        writePosition(s, 0.5); % 0.5 corresponds to 90 degrees if the servo is 0-180 degrees
        pause(30); % Wait 30 seconds
        
        % Move the arm back to 0 degrees
        writePosition(s, 0);
        pause(2); % Small delay to avoid bouncing or multiple reads
    end
end

Please note that the “writeposition” function takes a value between 0 and 1, where 0 corresponds to the minimum angle (0 degrees) and 1 corresponds to the maximum angle (typically 180 degrees). So, a value of 0.5 would set the servo to its midpoint, which is typically 90 degrees.

Also, this code assumes that the servo moves linearly across its range, which might not be the case for all servos. You may need to calibrate the position to get exactly 90 degrees if precision is important.

Further to know more about controlling servo motors you can refer to the below MathWorks Documentation:

https://in.mathworks.com/help/supportpkg/arduinoio/examples/control-servo-motors.html

Hope it helps,

Regards,

Shubham Shreshth