Generating synchronized digital signals on PXI-6723

[Khast]

Hi there,

I'm struggling with my PXI-6723 to generate 2 digital signals. i'm using the nidaqmx driver on Centos 6 via the C API. Because that is the only setup I have. I can also have access to a PXI-6515 device (32 digital In, 32 digital Out).

- The first signal is the synchronization signal @50kHz, 0 - 5V, duty cycle 50%

-> OK using the function DAQmxCreateCOPulseChanFreq on line Dev1/ctr0

- The second is the data signal, Logical 0 is 0V, logical 1 is 5V and each logical state must be centered on the rising edge of the synch signal for at least 2 µs.

-> NOK DAQmxCfgSampClkTiming with "Dev1/PFI0" as the source always fails with the error code -200077

2025-May-12 12:45:50.691820@Error@ITKBalise_Dev1:1@DAQMX error DAQmxCfgSampClkTiming(_kdata_task,"/Dev1/PFI0",1000.0,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000) (-200077): Requested value is not a supported value for this property.

I wired the ctr0 line with the pfi0 line, for the demonstration to simplify the code, I know there  is a way to do it by software.

Does the call fail due to my hardware not having this capability ? Or is it my code ? In the first case, can anybody forward me on a capable device (PCI(e) or PXI(e)) ?

Note : the example Digital/GenerateValues/WriteDigChan-extClk gives the same error.

[Khast]

I found out using NI MAX that this device only accepts "on demand" as an external clock.

When trying to generate N samples based on an external clock, the raised error states that only on demand sample clock is available.

Can anyone adress me a device that can generate a telegram based on an external clock ?

I understood that this kind of communication is called Serial Synchronous Interface as stated here : https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019MgLSAU&l=fr-FR*

[ZYOng]

Unfortunately, both PXI-6723 and PXI-6515 do not support hardware-timed digital output.

However, PXI-6723 does support hardware-timed analog output. You can do two channels up to 700kHz or 8 channels up to 100kHz for baud rate. I would recommend starting with the example C:\Users\Public\Documents\National Instruments\NI-DAQ\Examples\DAQmx ANSI C\Analog Out\Generate Voltage\Mult Volt Updates-Int Clk

[Khast]

Thanks for your comment !

I just found in the closet a PXI-6254, and it seems to accept my setup in NI MAX. 

I'll try with the real card tomorrow.

[Khast]

The PXI-6254 does the job ! Thanks for the leads to understand the cards behaviours.