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matlab-qd-PXILockIn.m
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matlab-qd-PXILockIn.m
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classdef PXILockIn < qd.classes.ComInstrument
%PXILOCKIN Digital Lock-In using NI-PXI chassis
% This is a software-based virtual Lock-in amplifier
% It uses a National Instruments PXI chassis with waveform generators
% and signal analysers to generate and measurem signals. All the
% processing is done in software on the computer, by a virtual
% instrument (called DigitalLockin) written in Python.
%
% Note that an instance of this instrument encompasses a full
% instance of the virtual lock-in software which governs a full PXI
% chassis and may contain several virtual lock-in amplifiers. You can
% select one by writing to the 'SELECT' channel.
% Supported commands:
% SELECT
% Select a lock-in instrument
% SET F|FS|A|T|PHASEOFFSET|MEASCH <value>
% Set the value of a variable of the selected lock-in instrument
% GET RPHIBUFFER
% Get multiline representation of all values of R and PHI acquired from
% the selected lock-in instrument since last time they were queried
% GET RPHI|R|PHI|XY|X|Y
% Get the last acquired values of R/PHI/X/Y from the selected lock-in
% This function may still return multiple values (comma-separated) when
% multiple channels are in use
% GET F|FS|A|T|PHASEOFFSET
% Get value of excitation/measurement control variable of selected lock-in instrument
% START
% Start measurements on the selected lock-in instrument
% STOP
% Stop measurements on the selected lock-in instrument
% CLOSE
% Close the selected lock-in instrument
% CLOSE ALL
% Close all lock-in instruments and exit
% PHASENULL
% Set the phase offset of the current lock-in instrument to the current phase
%
% TODO:
% * Create separate channels for each lock-in instead of requiring
% a manual setc('SELECT', <li>). E.g. one could make '1R', '2R',
% '1PHI', '2PHI' channels to specify which lock-in to take a
% channel from. [DONE for GET, not needed for SET]
% * Cache PHI when only R is requested and cache R when only PHI is
% requested. Also do some bookkeeping on which has already been
% requested and which hasn't
% * Make separate channels for each physical channel, i.e. instead
% of returning R and PHI as arrays make each element individually
% accessible as an instrument channel. One could make 'R1', 'R2',
% 'PHI1', 'PHI2' etc., or when combined with the first suggestion
% there would be '1R1', '2PHI1', '1PHI2' etc. Of course, any
% channel that has not been requested yet should be cached, and
% bookkeeping should be done of what has and has not been
% requested.
% * Maybe implement GET RPHIBUFFER
% Though it seems unlikely that this will ever be used
properties (Constant, GetAccess=private)
GENERIC_ERROR = 'An error occured. Check the virtual instrument window for details.';
end
properties (GetAccess=private)
r = [];
phi = [];
rphixyread = [];
numsetsubchans = 1;
end
methods
function obj = PXILockIn(com)
% Constructor
pcom = serial(com);
[email protected](pcom);
end
function rep = query(obj, req)
% Send command and read the response.
% Overridden because %s format string removed whitespace in the
% middle of the response.
% This function may be removed if the right behaviour is
% implemented in ComInstrument.
% This function also implements a debugging message but that does
% not have to go into the ComInstrument implementation
rep = query(obj.com, req, '%s\n', '%c');
if rep(end) == 10
rep = rep(1:end-1);
end
%fprintf(1, '%s : %s\n', req, rep);
end
function r = model(obj)
% Query the instrument for its make and model
r = obj.query('*IDN?');
end
function r = default_name(obj)
% Default name the instrument gets when no name is specified by the
% user
r = 'DigitalLockin';
end
function r = channels(obj)
% Get list of available channels. Needed because getc and setc will
% fail if the requested channel is not in this list, even if it
% exists and is readable/writable.
r = {'rphibuffer' 'rphi' 'r' 'phi' 'xy' 'x' 'y' 'f' 'fs' 'a' 't' 'phaseoffset' 'measch' 'select'};
if isempty(obj.rphixyread)
lastsubchan = 2*obj.numsetsubchans+1;
else
lastsubchan = (size(obj.rphixyread,2) - 1) / 2;
end
for cnt = 0:lastsubchan
r{end+1} = ['r(' num2str(cnt) ')'];
r{end+1} = ['phi(' num2str(cnt) ')'];
r{end+1} = ['x(' num2str(cnt) ')'];
r{end+1} = ['y(' num2str(cnt) ')'];
end
end
function val = getc(obj, channel)
% Get the value of a channel
% If the channel name is prefixed with a number, get the channel
% from the lock-in corresponding with that number
% Note that this selects the corresponding lock-in, and does not
% return to the previously selected one afterward
firstnonnumchar = 1;
while ~isnan(str2double(channel(1:firstnonnumchar)))
firstnonnumchar = firstnonnumchar + 1;
end
if firstnonnumchar > 1;
obj.set('SELECT', str2double(channel(1:firstnonnumchar-1)));
channel = channel(firstnonnumchar:end);
end
switch upper(channel)
case 'RPHIBUFFER'
error('DigitalLockin.GETC(RPHIBUFFER): Not yet implemented');
case {'RPHI', 'XY'}
response = obj.query(['GET ' channel]);
if length(response) > 2 && strcmp(response(1:2), 'OK')
val = str2num(response(4:end));
obj.rphixyread = ones(4, length(val));
else
obj.rphixyread = [];
error(['DigitalLockin.GETC(%s): ' obj.GENERIC_ERROR]);
end
case {'R', 'PHI', 'X', 'Y'}
%warning('DigitalLockin.GETC(%s): Requesting just one output channel at a time is not recommended unless you do not wish to use any other variables', channel);
response = obj.query(['GET ' channel]);
if length(response) > 2 && strcmp(response(1:2), 'OK')
val = str2num(response(4:end));
else
error(['DigitalLockin.GETC(%s): ' obj.GENERIC_ERROR], channel);
end
case {'F', 'FS', 'A', 'T', 'PHASEOFFSET'}
try
val = obj.querym(['GET ' channel], 'OK %f');
catch err
error('DigitalLockin.GETC(%s): %s Additional info from Matlab: %s', channel, obj.GENERIC_ERROR, err.message);
end
otherwise
% TODO reset stuff on getc(rphi)
if ~isempty(regexpi(channel, '(r|phi|x|y)\([0-9]+\)'))
ch = str2double(channel(end-1)); % Assume at most 10 physical channels
switch upper(channel(1))
case 'R'
readboolidx = 1;
case 'P'
readboolidx = 2;
case 'X'
readboolidx = 3;
otherwise
readboolidx = 4;
end
if isempty(obj.rphixyread) || obj.rphixyread(readboolidx, ch+1)
rphi = obj.getc('rphi');
if isempty(obj.r)
obj.r = rphi(1:(end+1)/2);
else
alpha = 1;
obj.r = (1-alpha) * obj.r + alpha * rphi(1:(end+1)/2);
end
obj.phi = rphi((end+3)/2:end);
obj.rphixyread(:,:) = 0;
end
obj.rphixyread(readboolidx, ch+1) = 1;
switch upper(channel(1))
case 'R'
val = obj.r(ch+1);
case 'P'
val = obj.phi(ch);
case 'X'
val = obj.r(ch+1) * cos(obj.phi(ch));
otherwise
val = obj.r(ch+1) * sin(obj.phi(ch));
end
else
error('DigitalLockin.GETC(%s): Unsupported channel.', channel);
end
end
%fprintf(1, 'GET(%s) = %s\n', channel, num2str(val));
end
function setc(obj, channel, val)
switch upper(channel)
case 'SELECT'
comcmd = ['SELECT ' num2str(val)];
case {'F', 'FS', 'A', 'T'}
comcmd = ['SET ' channel ' ' num2str(val)];
case 'MEASCH'
comcmd = num2str(val, '%d,');
if comcmd(end) == ','
comcmd = comcmd(1:end-1); % Remove comma
end
obj.numsetsubchans = length(strsplit(comcmd, ','));
comcmd = ['SET MEASCH ' comcmd];
case 'PHASEOFFSET'
if strcmp(num2str(val), 'now')
comcmd = 'PHASENULL';
else
comcmd = ['SET ' channel ' ' num2str(val)];
end
otherwise
error('DigitalLockin.SETC(%s=%s): Unsupported channel.', channel, val);
end
if strcmp(obj.query(comcmd), 'ERROR')
error('DigitalLockin.SETC(%s=%s): %s.', channel, num2str(val), obj.GENERIC_ERROR);
end
end
function start_lockin(obj)
if strcmp(obj.query('START'), 'ERROR')
error('DigitalLockin.SELECT(%s): %s.', num2str(value), obj.GENERIC_ERROR);
end
end
function stop_lockin(obj)
if strcmp(obj.query('STOP'), 'ERROR')
error('DigitalLockin.STOP_LOCKIN(): %s.', obj.GENERIC_ERROR);
end
end
function close_all(obj)
if strcmp(obj.query('CLOSE ALL'), 'ERROR')
error('DigitalLockin.CLOSE_ALL(): %s.', num2str(value), obj.GENERIC_ERROR);
end
obj.read();
obj.delete();
end
end
end