using timer in MATLAB to extract the system time

Question

!I am using MATLAB to design an Analog Clock. Currently, my code simply displays the (or plots rather) the clock design with the hands (hours, mins, secs) and does not tick. Here is my code:

function raviClock(h,m,s)
drawClockFace;


%TIMER begins-------
t = timer;
t.ExecutionMode = 'FixedSpacing';  %Use one of the repeating modes
t.Period = 1;                      %Fire on 1 second intervals
t.TimerFcn = @timer_setup;           %When fired, call this function
start(t);
set(gcf,'DeleteFcn',@(~,~)stop(t));
end

function timer_setup(varargin)

format shortg;
timenow = clock;
h = timenow(4);
m = timenow(5);
s = timenow(6);

% hour hand
hours= h + m/60 + s/3600;
hourAngle= 90 - hours*(360/12);

% compute coordinates for pointing end of hour hand and draw it
[xhour, yhour]= polar2xy(0.6, hourAngle);
plot([0 xhour], [0 yhour], 'k-','linewidth',7.4)

% minute hand
mins= m + s/60;
minsAngle= 90 - mins*(360/60);

% compute coordinates for pointing end of minute hand and draw it
[xmins, ymins]= polar2xy(0.75, minsAngle);
plot([0 xmins], [0 ymins], 'r-','linewidth',4)


%second's hand
second = s;
secAngle = 90- second*(360/60);

[xsec, ysec]= polar2xy(0.85, secAngle);
plot([0 xsec], [0 ysec], 'm:','linewidth',2)
%end   % while ends
end

%--------------------------------------------------------

function drawClockFace

%close all          
axis([-1.2 1.2 -1.2 1.2])  
axis square equal
hold on            


theta= 0;
for k= 0:59
    [xX,yY]= polar2xy(1.05,theta);
        plot(xX,yY,'k*')

        [x,y]= polar2xy(0.9,theta);
    if ( mod(k,5)==0 )  % hour mark
        plot(x,y,'<')
    else                % minute mark
        plot(x,y,'r*')
    end
    theta= theta + 360/60;
    end
end

%-----------------------------------------------------------------
function [x, y] = polar2xy(r,theta)

rads= theta*pi/180;  
x= r*cos(rads);
y= r*sin(rads);
end

This is simply taking a static data of values for the HOUR, MINUTE and SECOND arguments when i initially call my function. I tried using the following in a while loop but it didn't help much

format shortg
c=clock
clockData = fix(c)
h = clockData(4)
m = clockData(5)
s = clockData(6)

and passing the h, m and s to the respective cuntions. I want to know how I can use the TIMER obkjects and callbacks for extracting the information of [hrs mins secs] so i can compute the respective point co-ordinates in real time as the clock ticks.

Answer 1

I'd do a couple of things here.

First, you probably don't really need to pass the h, m, s inputs, if you are displaying current time. Add this to the top of your function to auto set these variables.

if nargin == 0
    [~,~,~,h,m,s] = datevec(now);
end

Then, it is pretty easy to use a time to call this function periodically. Something like this.

t = timer;
t.ExecutionMode = 'FixedSpacing';  %Use one of the repeating modes
t.Period = 1;                      %Fire on 1 second intervals
t.TimerFcn = @(~,~)raviClock;      %When fired, call this function (ignoring 2 inputs)
start(t);                          %GO!

Use docsearch timer for in depth documentation of the timer objects. But the code above should get you started.

To stop the timer, run

stop(t);

To stop the timer when the window is closed, put the stop command into the window deletion callback:

set(gcf,'DeleteFcn',@(~,~)stop(t));  %NOte:  Better to explicitly use a figure number, rather than gcf.