% Remote control of a function-generator by GPIB from Matlab ICT.
%      Hewlett-Packard 33120A '15MHz function / arbitrary waveform generator'.
%
% This script is (relatively) short and clear because it uses a 
% separate function fg_cmd() that does most of the work.
% 
% 2010-02-16.  
% Nathaniel.
%


%% open the function generator instrument and do basic settings

global ih;
fg_cmd('!!CONNECT!!');



%% set up an 'arbitrary waveform' on the function generator


Vpk = 2.5;  % peak voltage
f   = 50; % frequency at which to repeat the waveform-data
Vdc = 0.0;  % offset voltage (dc level)

% how many points to use:  min is 8, max is 16000
N = 1024;

% make the waveform: as an example, let's have a first-half of
% a sinusoid, then a possible gap (zero) then the other half
% of the sinusoid, then a similar gap

% how much of the total time should be on the sinusoid (nonzero)
duty = 0.5;

% the signal
s = [ ...
    sin( linspace(0, pi, round(N*duty/2)) ),  ...
    zeros(1, round(N*(1-duty)/2)), ...
    sin( linspace(pi, 2*pi, round(N*duty/2)) ),  ...
    zeros(1, round(N*(1-duty)/2)) ...
    ];


% check/correct number of points (arkward duty cycles might
% have caused rounding errors when generating s)
if length(s)>N,
    s = s(1:N);
    warning('the auto-generated data has been truncated');
elseif length(s)<N,
    s = [s, zeros(1,N-length(s))];
    warning('the auto-generated data had been zero-padded');
end

% write the data as waveform data in binary form
% (it gets normalised so that the largest magnitude in 's' 
% will always be the largest available number in the 
% function-generator's memory)
fg_cmd(s);

% name the data, set it as active, set amplitude and frequency
fg_cmd(  {
    'DATA:COPY DIAGWAVE, VOLATILE'
    'FUNC:USER DIAGWAVE'
    sprintf('FREQUENCY %f', f)
    'OUTPUT:LOAD 50'  % assume 50ohm load (so, double the voltage)
    sprintf('VOLTAGE %f', Vpk)
    sprintf('VOLTAGE:OFFSET %f', Vdc)
    'FUNC:SHAP USER'  }  );



%% close the connection

fg_cmd('!!DISCONNECT!!');