Fractional divider snippet

fractdiv_snippet.m

Fc    = 10;  % clock frequency
Tfreq = 4;   % Target frequency

% working options
n  = 100000;  % number of points
SR = 10*Fc;   % sampling rate
T  = n/SR;    % sampling time (s)

% working vectors
t = 0:1/SR:T-1/SR; % time vector
w = square(2*pi*2*Fc*t);
out = zeros(1,n);

% calculate counters
idiv = Fc / Tfreq;
rem  = mod(Fc,Tfreq);
icounter_max = floor(idiv);
fcounter_max = round(Fc/rem);

% main loop
icounter = 0;
fcounter = 0;
last_v   = 0;
vout     = 0;

for i = 1:length(w);
    v = w(i);
    
    if (v == 1) && (v ~= last_v) % raising edge
        fcounter = fcounter + 1;
        
        if (fcounter == fcounter_max)
            fcounter = 0;
        else
            icounter = icounter + 1;
        end
    end

    if (icounter >= icounter_max)
        vout = 1 - vout; % toogle output
        icounter = 0;
    end
    
    out(i) = vout;
    last_v = v;
end

out;