data acquisition setup

datacapture.m

% ME224 Basic Data Output Script

try
   stop(ai); delete(ai);
catch
end

% Settings
Fsi = 1000; % input sample rate
time_length = 1; % length of time to capture samples (seconds)
samples = time_length*Fsi; % How many samples to get

channels = 0; % Channels to get data on

% Get Handle for Analog Output Device
mccdaqinfo = daqhwinfo('mcc');
mccdaqids = find(ismember(mccdaqinfo.BoardNames,'USB-1208FS')==1);

% Create AO and AI handles
ai = analoginput('mcc', mccdaqinfo.InstalledBoardIds{mccdaqids(1)});

addchannel(ai,channels,'in');

set(ai,'SampleRate',Fsi);
set(ai,'SamplesPerTrigger',samples);

start(ai);
data = getdata(ai,samples);

filttest.m

% ME224 Basic Data Output Script

try
   stop(ao); delete(ao);
catch
end

try
   stop(ai); delete(ai);
catch
end

% Settings
Fso = 10000; % output sample rate
Fsi = 10000; % input sample rate
time_length = 5; % length of time to capture samples (seconds)
samples = time_length*Fsi; % How many samples to get

channels = 0; % Channels to get data on

% Get Handle for Analog Output Device
mccdaqinfo = daqhwinfo('mcc');
mccdaqids = find(ismember(mccdaqinfo.BoardNames,'USB-1208FS')==1);

% Create AO and AI handles
ao = analogoutput('mcc', mccdaqinfo.InstalledBoardIds{mccdaqids(2)});
ai = analoginput('mcc', mccdaqinfo.InstalledBoardIds{mccdaqids(1)});

addchannel(ao,channels,'out');
addchannel(ai,channels,'in');

set(ao,'SampleRate',Fso);
set(ai,'SampleRate',Fsi);
set(ai,'SamplesPerTrigger',samples);

t = 0:1./Fso:time_length-1./Fso;
outdata = (chirp(t,0.1,time_length-0.3,500)+1)';

putdata(ao, outdata);
start(ai);

start(ao);
[data time]= getdata(ai,samples);
flushdata(ai) % get rid of any queued data

figure(1);
[X,f] = myFFT(data - mean(data),Fsi);
[Xo,fo] = myFFT(outdata - mean(outdata),Fso);
plot(f,smooth(abs(X./Xo)));
set(gca,'xlim',[0 500]);
set(gca,'ylim',[0 3]);
xlabel('Frequency (Hz)')
ylabel('Vo/Vin')

myFFT.m

function [X,freq]=myFFT(x,Fs)

x = x';
N = length(x);

if mod(N,2)
    k = (-(N-1)/2):((N-1)/2); % if odd, use symmetrical k
else
    k = (-N/2):((N-1)/2); % if even, one extra negative value
end

Tlen = N/Fs;
freq = k./Tlen; % scale k by time length to get frequencies
X=fft(x)./N; % scale fft by length
X=fftshift(X);