function [adfreq, n, ts, fn, ad] = plx_ad(filename, ch)

% plx_ad(filename, channel): Read a/d data from a .plx file

%

% [adfreq, n, ts, fn, ad] = plx_ad(filename, ch)

%

% INPUT:

%   filename - if empty string, will use File Open dialog

%   channel - 0 - based channel number

%

%           a/d data come in fragments. Each fragment has a timestamp

%           and a number of a/d data points. The timestamp corresponds to

%           the time of recording of the first a/d value in this fragment.

%           All the data values stored in the vector ad. 

% OUTPUT:

%   n - total number of data points 

%   ts - array of fragment timestamps (one timestamp for fragment, in seconds)

%   fn - number of data points in each fragment

%   ad - array of raw a/d values



if(nargin ~= 2)

   disp('2 input arguments are required')

   return

end



i = 0;

n = 0;

ts = 0;

fn = 0;

ad = 0;



if(length(filename) == 0)

   [fname, pathname] = uigetfile('*.plx', 'Select a plx file');

	filename = strcat(pathname, fname);

end



fid = fopen(filename, 'r');

if(fid == -1)

	disp('cannot open file');

   return

end



% calculate file size

fseek(fid, 0, 'eof');

fsize = ftell(fid);

fseek(fid, 0, 'bof');





disp(strcat('file = ', filename));



% read file header

header = fread(fid, 64, 'int32');

freq = header(35);  % frequency

ndsp = header(36);  % number of dsp channels

nevents = header(37); % number of external events

nslow = header(38);  % number of slow channels

npw = header(39);  % number of points in wave

npr = header(40);  % number of points before threshold

tscounts = fread(fid, [5, 130], 'int32');

wfcounts = fread(fid, [5, 130], 'int32');

evcounts = fread(fid, [1, 512], 'int32');



% A/D counts are stored in evcounts (301, 302, etc.)

count = 0;

if evcounts(301+ch) > 0

	count = evcounts(301+ch);

	ad = [1:count];

end



% skip DSP and Event headers

fseek(fid, 1020*ndsp + 296*nevents, 'cof');



% read one A/D header and get the frequency

adheader = fread(fid, 74, 'int32');

adfreq = adheader(10);



% skip all other a/d headers

fseek(fid, 296*(nslow-1), 'cof');



record = 0;



wf = zeros(1, npw);

adpos = 1;



while feof(fid) == 0

   type = fread(fid, 1, 'int16');

	upperbyte = fread(fid, 1, 'int16');

	timestamp = fread(fid, 1, 'int32');

	channel = fread(fid, 1, 'int16');

   unit = fread(fid, 1, 'int16');

   nwf = fread(fid, 1, 'int16');

   nwords = fread(fid, 1, 'int16');

   if nwords > 0

      wf = fread(fid, [1 nwords], 'int16');

   end

   if nwords > 0

   	if type == 5

         if channel == ch 

        	i = i + 1;

			n = n + nwords;

         	ts(i) = timestamp/freq;

			fn(i) = nwords;

			if count > 0

			    if adpos+nwords-1 <= count

				    ad(adpos:adpos+nwords-1) = wf(1:nwords);

					adpos = adpos + nwords;

				else

					for i=1:nwords

						ad(adpos) = wf(i); adpos = adpos + 1;

					end

				end

			else

				ad = [ad wf(1, 1:nwords)];

			end

      	end

   	end

   end

   

   record = record + 1;

   if mod(record, 1000) == 0

       disp(sprintf('records %d points %d (%.1f%%)', record, n, 100*ftell(fid)/fsize));

   end



   if feof(fid) == 1

      break

   end

   

end



if adpos-1 < count

   ad = ad(1:adpos-1);

end



disp(strcat('number of data points = ', num2str(n)));



fclose(fid);