DAQmx examples

Examples of talking to a National Instruments (NI) DAQ card without the data acquisition toolbox.

Examples of using matlab to talk to a National Instruments (NI)
DAQ card _without_ the 'data acquisition toolbox'

I have mainly used code and examples from Jens Roesner here:
http://www.jr-worldwi.de/work/matlab/index.html
However, I had to make a few slight tweaks to get it to work for me. I have only tested this on Matlab 7.8.0 (R2009a) on WinXP with a NI PCI 6220 board, so no guarantees.

Using Jens' code, I got an error -200088 whenever I tried to create a channel. To get it working, I had to change the initial task handles to uint32([]) which then returned a pointer for taskhandle

I also had trouble with creating tasks, then losing the taskhandle, and not being able to create the same task because of a name conflict. The solution is to not name any of the tasks - names don't seem to be useful anyway. So all my functions pass an empty string as a name.

Other changes are just cosmetic -
made functions for common tasks to simplify my main code
put all task handles in structure so easy to clear