Using DAQmxWriteDigitalScalarU32 to write channels sharing same port(s)?

[evizz]

Hello,

I have a USB-6509 and NI-DAQmx 15.5.1 installed. Using the ansi c api.

Is it possible to create several independent channels that use different lines from the same port?

DAQmxCreateTask("",&th1)

DAQmxCreateDOChan(th1,"Dev1/line0:4","",DAQmx_Val_ChanForAllLines)

DAQmxStartTask(th1)

DAQmxCreateTask("",&th2)

DAQmxCreateDOChan(th2,"Dev1/line5:9","",DAQmx_Val_ChanForAllLines)

DAQmxStartTask(th2)

....

and repeat for the following channels:

Dev1/line0:4
Dev1/line5:9
Dev1/line10:14
Dev1/line15:19
Dev1/line24:28
Dev1/line29:33

So I can use DAQmxWriteDigitalScalarU32 to write to each task independently?

for example:

DAQmxWriteDigitalScalarU32(th1,1,10,0x1,NULL)

DAQmxWriteDigitalScalarU32(th2,1,10,0x2,NULL)

DAQmxWriteDigitalScalarU32(th3,1,10,0x3,NULL)

...

DAQmxWriteDigitalScalarU32(th6,1,10,0x6,NULL)

Will these tasks interfere with each other since they use the same port, but are assigned different lines?

If not, do I need to bit shift the data if the task/channel doesn't start at line Px.0?

Thanks!

[niarena · Accepted solution]

yes, as long as you are not using the same line on different channels, they should not interfere with each other for that reason, you can create a channel per line if you want

From the help reference of the DAQmxWriteDigitalScalarU32 function:
"Writes a single 32-bit unsigned integer sample to a task that contains a single digital output channel. Use this format for devices with up to 32 lines per port."

http://zone.ni.com/reference/en-XX/help/370471AC-01/daqmxcfunc/daqmxwritedigitalscalaru32/

so yes too, the DAQmxWriteDigitalScalarU32 can write to each task independently

[evizz]

Thanks!

I just received my usb-6509 today and sure enough it works! Also verified that I do have to shift bits based on where the line starts in a port.

Is there a way to readback the bits that were written on a digital output channel? It would be nice to verify the correct value was written.

[niarena]

Hi evizz

how about with the printf function? 

check this other forum, they used it to check the output status

https://forums.ni.com/t5/LabWindows-CVI/PCI-6528-Digital-output/m-p/564405

[evizz]

Nice, so DAQmxReadDigitalScalarU32 will work on a DO channel? I tried it with the simulator, but no go.

[niarena]

they said the state was always 0, I don't know why they were using that function with a DO channel on the other forum, that function is used on a DI channel to read the input, not the output, check the help for that function

http://zone.ni.com/reference/en-XX/help/370471AE-01/daqmxcfunc/daqmxreaddigitalscalaru32/