problem with 'Filter function' while filtering data, acquired from NI DAQ Board

I am trying to filter the sampled square wave output from the DAQ,coming from amplifier. Input frequency is 5.2 Hz. so i had set the cut off frequency to 5.5 hz. and filter order of 100.

when i execute the below matlab code, i am getting error " Error using fdesign.abstracttype/window (line 12) Frequency specifications must be between 0 and 1.

Error in fdesign.abstracttype/superdesign (line 126) Hd = feval(method, this, varargin{:},sysObjArgsDesign{:});

Error in fdesign.abstracttype/design (line 11) varargout{1} = superdesign(this, varargin{:});

Error in filter_daq (line 25) Hd1 = design(Hf,'window','window',@hamming,'SystemObject',true); "

what could be the reason for this error. It would be of great help if let me know the reason. Here is my code for the same.

i
p.TriggerTimeout        = 2; %If there is no trigger signal after 2 seconds time out 
p.no_of_measurements    = 50;
p.InputRange            = [-2 2]; %Amplifier output DAQ AI options [-10 10], [-5 5], [-2 2],[-1 1],[-500 500], [-200 200], [-100 100]
p.AInputChannel         = 0;
p.Frequency             = 5;                    %in kHz
p.noise                 = 0.065;
p.no_of_measurementRuns = 6;
ai = analoginput ('nidaq','Dev1');
ch = addchannel(ai,p.AInputChannel,{'PD'}); %Connect the amplifier output to AI0(+) and AI0(-) NRSE
duration = 10;
set(ai,'SampleRate',20000)
ActualRate = get(ai,'SampleRate');
set(ai,'SamplesPerTrigger',duration*ActualRate)
set(ai,'TriggerType','Manual')
blocksize = get(ai,'SamplesPerTrigger');
Fs = ActualRate;
ch.InputRange = p.InputRange;
start (ai);
trigger(ai)
wait(ai,duration + 1)
[data, time] = getdata (ai);
Fc    = 5.5;
N = 100;   % FIR filter order
Hf = fdesign.lowpass('N,Fc',N,Fc);
Hd1 = design(Hf,'window','window',@hamming,'SystemObject',true);
%Hd2 = design(Hf,'window','window',{@chebwin,50},'SystemObject',true);
hfvt = fvtool(Hd1,Hd2,'Color','White');
legend(hfvt,'Hamming window design','Dolph-Chebyshev window design')
y = filter (Hd1,data);
plot (time, y);