Currently we are using LabWindows/CVI with a 96 bit DIO card (PXI-6509).
What we have found and NI support confirmed is that with the following the software needs to be aware of the bit offset during a write to one or more lines on a port.
Virtual Channel Physical Channel
dataEnable dev1/port0/line 2
Our assumption was that writing to 'dataEnable' a value of 1 using DAQmxWriteDigitalU8() would write to the virtual channel 'dataEnable'. What we found is that is not the case. We need to write a value of 0x04. But that the bits that are set to zero in this value written to 'dataEnable' have no affect on other lines on the port that are already set. This gives us the impression that the driver has knowledge of what bit position we are trying to write too.
So based on this why is it not possible that when I call from LabWindows/CVI to do a write to a virtual channel I cannot just do something like this:
Virtual Channel Physical Channel
dataEnable_Clk dev1/port0/line2:3
Line 2 = dataEnable
Line 3 = dataClk
write( dataEnable_Clk, 1) // to set enable line high
write( dataEnable_Clk, 3) // to keep enable line high and raise clk line
write( dataEnable_Clk, 1) // keep enable line high and lower clk line
write( dataEnable_Clk, 0) // lower enable line
** assumption is that seperate lines on another port are used to present the data to the external hardware and are not shown here. The data would have bee setup before the sequence above and then change data and repeat sequence as needed.
Here I don't have to keep in mind that Enable is on line 2 and Clk is on line 3 or have to setup values of 0x04 for hte Enable and 0x08 for the Clk. If I have to do this I would rather have direct access to each port to just write the values directly. i know there is the register level I can use but doing this at a higher level is better.
In our code when a internal function is called to write data we would like to just write a value out to the virtual channel and not have to figure out the bit alignment to shift over the value to use one of the current functions.
Let me know your thoughts.
Bob Delsescaux
