I started trying to write a way to control
hardware that allows a user to organise hardware based on what they
have, and using a configuration file to define what signals (channels)
are connected to what line on hardware.
I found
http://forums.ni.com/ni/board/message?board.id=180&message.id=38304&query.id=363765#M38304
I
have defined an unnamed task, with a single channel "Ignition" as
"Dev0/port0/line4" in a config file. My software loads this config and
calls DAQmxCreateTask() and DAQmxCreateDOChan(task, "Dev0/port0/line4",
"Ignition", DAQmx_Val_ChanForAllLines). On another computer with the
same software, but different configuration file, this might be
"Dev1/port1/line2".
I'm
using the function DAQmxWriteDigitalScalarU32 to set this port and
clear it. How can I determine the correct value when using
DAQmxWriteDigitalScalarU32()? A value of 1 generally won't work (unless
it's portX/line0)
One
solution I have is to write -1 (0xFFFFFFFF), but then if I define
multiple lines separated by commas, both lines will be set and I still
have the problem if I want to separate them.
Like
in the forum highlighted, the original user had initially expected that
the DAQmx drivers would do the automatic bitshifting. Since it doesn't,
I'm wanting to do that myself (for both reads and writes). So I need to
understand how DAQmx internally takes the U32 and maps that to physical
hardware. This will then become a DLL internally in our company for
multiple programs and configurations.
Some notes:
I
found that "Dev0/port2, Dev0/port1" means the lower 8 bits writes to
port 2 and upper 8 bits writes to port 1. Is this only for 8-bit
hardware (I've tested on a USB 6501, but I also have downstairs in my
lab a PCI-DIO-96 card).
If I have 5 lines, over 5 ports, does this imply I can't use DAQmxWriteDigitalScalarU32()?
Thanks in advance,
Jason.
