First argument provided is not valid for addlistener

I'm trying to pipe some data from and acquisition device to a function. The function is stored in separate file and is added to the working directory earlier in the code so Matlab finds the function ok but I get the error report below any ideas? (section of code added, Channel in use is AI)

Regards Stu

??? First argument provided is not valid for addlistener. (Check its type or validity)

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n_ch=1; % the number of channels in use
% Preparing and setting uo the DAQ card (NI USB-6210)
AI=analoginput('nidaq','Dev1');

% set to single ended, Fs and durationid1
set(AI,'InputType','SingleEnded')
chan=addchannel(AI,0:(n_ch-1)); % create number of channels

SampleRate = 2000;          % used as frequency content exceeds 500hz
cd C:\Users\Ghost\Desktop\MATLab\
addpath(' C:\Users\Ghost\Desktop\MATLab\Codes')
addpath(' C:\Users\Ghost\Desktop\MATLab\Functions')

% set Fs and durarion

set(AI,'SampleRate',SampleRate);
set(AI,'SamplesPerTrigger',inf);
set(AI,'TriggerType','Manual');
set(AI,'TriggerRepeat',0);

    type('.\Functions\emg_processing.m')
    addlistener(AI,'DataAvailable', @emg_processing);
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function emg_processing(src, event, newdata)

end

[Jan]

Who has written this code?

[jenni]

I too have encountered the same problem. Did you find the solution?