How do I perform buffered digital I/O using the Data Acquisition Toolbox?

I need to be able to set up a buffered acquisition with external trigger and external clock and use a DMA transfer after the acquistion is completed. I would like to know the complexity level with doing this with the Data Acquisition Toolbox.

Answer 1

[MathWorks Support Team]

This enhancement has been incorporated in Release 2012a (R2012a). For previous product releases, read below for any possible workarounds:

The Data Acquisition Toolbox does not directly support buffered DIO or handshaking (latching) at this time. However, you can write your own MATLAB code to support this functionality.

If you want to do it in MATLAB code using callbacks, here is an example showing how to do it. This example is for output.

1. Create a MATLAB file to handle the output. The file should be saved as dooutput.m (for the example; it can be named anything for other instances) and have the following contents:

function dooutput(obj, event)

% The UserData field is the common way of passing data around.

% In this example it holds a struct with two fields, 'count'

% the number of times the function has been called and 'data'

% which is the data to be output.

outdata = obj.UserData

if (outdata.count < length(outdata.data))

      outdata.count = outdata.count + 1;

      putvalue(obj, outdata.data(outdata.count, :));

else

      stop(obj)

end

obj.Userdata = outdata;

% end of MATLAB file

2. In MATLAB do the following:

% Generate the output data.

data = myData(...);

% Create the object, add the dio lines

obj = dio('nidaq', 1);

addline(obj, 1:8, 'out');

% Configure the callbacks

obj.TimerFcn = @dooutput;

obj.TimerPeriod = .01;

% Setup the userdata

outdata.count = 0;

outdata.data = data;

obj.UserData = outdata;

% Start the output

start(obj)