function current=vstimulate(pre, frequency, gain, scaling, varargin)
%
% VSTIMULATE
%
%    CURRENT = VSTIMULATE(PRE, FREQUENCY, GAIN, SCALING)
%               outputs a pulse of 100mV and 1 msec on the PRE
%               channel at FREQUENCY and returns whatever it
%               finds on both the channels.  GAIN and SCALING
%               need to be specified, otherwise 1 (V/nA) and
%               100 (mV/V) are assumed.  Uses VSTIM to
%               actually deliver the stimulus.
%
%    CURRENT = VSTIMULATE(PRE, FREQUENCY, GAIN, SCALING, NREPEAT)
%               repeats the above operation NREPEAT times.
%

if pre == 1 
	post = 2;
else
	pre = 2;
	post = 1;
end

if frequency <= 0
	frequency = 1000;
end

if gain <= 0
	gain = 1;     % the output gain of the amp, in V/nA
end

if scaling <= 0
	scaling = 100;   % the input scaling of the amp, in mV/V
end

if nargin==5
	n=varargin{1};
else
	n=1;
end

mV=100;       % amplitude of the pulse (in mV)

pulse=mV*[zeros(0.2*frequency,1); ones(10,1); zeros(0.8*frequency - 10,1)];
nothing=zeros(frequency,1);

stim=zeros(frequency,2);
stim(:,pre)=pulse;
stim(:,post)=nothing;

current = vstim (stim, scaling, gain, frequency, n);