matlabvisaspmd

Read two visa instruments in parallel with Matlab

I try to read data from two Keysight oscilloscopes in parallel with Matlab (2015a). To do that I use the parallel computing toolbox with the spmd command. I have a function to read the data which accepts a visa object as parameter and returns the rawdata. This works fine outside the spmd command like this (scope1 and scope2 are open visa objects):

scope = {scope1, scope2}
scopedata1 = scopeGetCh1Raw(scope{1});
scopedata2 = scopeGetCh1Raw(scope{2});

I get the data from both oscilloscopes.

If I do:

spmd
    scopedata = scopeGetCh1Raw(scope{labindex});
end

I get the following error:

Error detected on workers 1 2.

Caused by:
    Error using icinterface/fprintf (line 147)
    OBJ must be connected to the hardware with FOPEN.
    Error using icinterface/fprintf (line 147)
    OBJ must be connected to the hardware with FOPEN.

Any ideas what's going wrong?

Cheers Nils

Solution

  • The workers operating on the body of your spmd block are separate processes. I presume you'll need to call fopen inside spmd, something like:

    spmd
    myScope = fopen(...); % do whatever to open the scope
    scopedata = scopeGetCh1Raw(myScope);
end