Acquire data using attached 6218 DAQ in MATLAB and plot FFT

yang_dataacq.m

% Clear out old handles for devices
try
    stop(ai)
    delete(ai)
catch
end

% Settings
Fs = 100000; % Number of samples to collect per second
time_length = 2; % length of time to capture samples (seconds)
samples = time_length*Fs; % How many samples of data to get
channels = [0]'; % Channels to get data on

% Get Handle for Analog Input Device
daqinfo = daqhwinfo('nidaq');
daqid = find(ismember(daqinfo.BoardNames, 'USB-6218')==1);
ai= analoginput('nidaq', daqinfo.InstalledBoardIds{daqid});

% Apply settings to device
addchannel(ai,channels,'in');
setverify(ai.Channel,'InputRange',[-5 5]);
setverify (ai,'SampleRate',Fs);
setverify(ai,'InputType','SingleEnded');
setverify(ai,'SamplesPerTrigger', samples);

start(ai);
wait(ai,time_length+1);
[data, dtime, abstime,events]= getdata(ai, samples);
flushdata(ai);           % get rid of any queued data

%%

L = length(data);
NFFT = 2^nextpow2(L);
UDATA = fft(data,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
figure; clf;
sig_mag = 2*abs(UDATA(1:NFFT/2+1));
[pk n] =  max(sig_mag);
f(n)
semilogy(f,sig_mag);
set(gca,'xlim',[0 4000])