mccUsbErb24(arg1)

function relay = mccUsbErb24(arg1)
% Constructor for the class representing an Measurement Computing relay
% card, USB-ERB24. This class uses the DAQ object's UserData to store
% information about this object that isn't already embedded in the DAQ
% object.
% 
%
% Behavior:
%
%   relayCard = mccUsbErb24();  % object is initialized with the first
%                               % constructor from 
%                               % daqhwinfo('mcc','ObjectConstructorName')
%                               % whose BoardName is 'USB-ERB24'
%                               % same as relayCard = mccUsbErb24(1);
%
%   relayCard = mccUsbErb24(i); % returns an initialized relay object, the 
%                               % non-empty constructor from daqhwinfo
%                               % indexed by the input number whose
%                               % BoardName is also 'USB-ERB24'.
%
%   relayCard = mccUsbErb24(daqObj); % creates the object with the given
%                                    % relay card w/re-initialized lines. 
%                                    % Throws an error if it's not a 
%                                    % USB-ERB24.
%
%   on(relayCard,1:24);         % turns on all relays
%   off(relayCard,2:2:24);      % turns off even-numbered relays
%   off(relayCard,1);           % turns off first relay
%   off(relayCard,1:24);        % turns off all relays
%
%   clear relayCard     % Removes var from workspace, but retains hardware
%   and all information in this session. An identical object can be created
%   by calling this constructor on the daq object directly, provided the
%   object's UserData hasn't been externally modified.
%
% TODO: for the first two uses, check daqfind() for valid cards before
% constructing them from scratch.

boardName = 'USB-ERB24';

%relay.devObj = [];

switch nargin
    case 0
        relay = mccUsbErb24(1);
        return
    case 1
        if isnumeric(arg1)
            idx = arg1; % it's an index into the constructors
            if idx < 1
                error('Relay card index must be an integer >= 1')
            end
            relay = mccUsbErb24(initMccUsbErb24(idx));
            return
        elseif isa(arg1,'mccUsbErb24')
            relay = arg1;
            return
        elseif isa(arg1,'digitalio') && strcmp(daqhwinfo(arg1, 'DeviceName'), boardName)
            relay.devObj = initLines(arg1);
        else
            error('mccUsbErb24: first argument must be a number or digitalio object of ''USB-ERB24''')
        end
    otherwise
        error('Constructor expects 0 or 1 argument. %d were given.', nargin)
end
    
% TODO: maybe inherit from the DAQ object instead of just embedding it?
% relay = class(relay, 'mccUsbErb24', relay.devObj)
relay = class(relay, 'mccUsbErb24');
off(relay,1:24);

%% initMccUsbErb24()
function relayCard = initMccUsbErb24(idx)
% Initializes the DAQ hardware
mccHardware = daqhwinfo('mcc');
constructorIdx = strcmp(mccHardware.BoardNames, 'USB-ERB24');
constructors = mccHardware.ObjectConstructorName(constructorIdx, :); % get only valid cards
emptyRowIdx = all(cellfun('isempty',constructors),2);
constructors = constructors(~emptyRowIdx, :); % eliminate rows that are entirely empty
if isempty(constructors)
    error('Could not find any USB-ERB24 relay cards. Check hardware is installed and restart MATLAB.')
elseif idx > size(constructors,1)
    error('Only %d USB-ERB24 relay card(s) are installed. The index %d is too high.', size(constructors,1),idx)
end

% Now construct it
constructor = [constructors{idx,:}];
relayCard = eval(constructor);
relayCard = initLines(relayCard);

%% initLines()
function relayCard = initLines(relayCard)
% If lines exist, then delete them
if length(relayCard.Line) > 0
    delete(relayCard.Line)
end
% Now setup the lines to make sense
addline(relayCard, 0:7, 2, 'out'); % configure relays 1-8 as outputs
addline(relayCard, 0:7, 3, 'out'); % configure relays 9-16 as outputs
addline(relayCard, 0:3, 0, 'out'); % configure relays 17-20 as outputs
addline(relayCard, 0:3, 1, 'out'); % configure relays 12-24 as outputs