USB845x single DIO pulse with specific length

[RudyTS]

Hi, I have integrated the USB845x using python ctypes to use the DIO. I want to output a single pulse with the length of 10 microsecond. However, I am able to do it with the minimum length of 250 microsecond using the C API. Maybe there is a overhead of using python to access the NI USB845x. Is there a specific code to make sure it pulse maximum of 10 microsecond?

Here is my code for the python DIO pulse:

portNum = 0

    lineNum = 0

    writeData = 1

    offData = 0

    check_error(ni845x_dll.ni845xDioWriteLine(dev_handle,portNum, lineNum, writeData))

    # time.sleep(0.00001)

    start = time.perf_counter()

    while (time.perf_counter() - start) < 10e-6:

        pass

    check_error(ni845x_dll.ni845xDioWriteLine(dev_handle,portNum, lineNum, offData))

I have tried time.sleep and even run it without both type of delay. The smallest will still be 200+ microsecond.
Thanks in advanced.

[crossrulz · Accepted solution]

You are hitting a limit of using Windows/software timing.  What you really need is a counter output (if using a DAQ) or Function Generator that can output a pulse.  If on a hardware budget, I would probably just get a Raspberry Pi Pico and program it to do my pulse.  Even a Pi5 might be able to do it (I have not played around with one yet, so I do not know what kind of timing is possible on it).

[santo_13]

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@RudyTS wrote:

Hi, I have integrated the USB845x using python ctypes to use the DIO. I want to output a single pulse with the length of 10 microsecond. However, I am able to do it with the minimum length of 250 microsecond using the C API. Maybe there is a overhead of using python to access the NI USB845x. Is there a specific code to make sure it pulse maximum of 10 microsecond?

Here is my code for the python DIO pulse:

portNum = 0

    lineNum = 0

    writeData = 1

    offData = 0

    check_error(ni845x_dll.ni845xDioWriteLine(dev_handle,portNum, lineNum, writeData))

    # time.sleep(0.00001)

    start = time.perf_counter()

    while (time.perf_counter() - start) < 10e-6:

        pass

    check_error(ni845x_dll.ni845xDioWriteLine(dev_handle,portNum, lineNum, offData))

I have tried time.sleep and even run it without both type of delay. The smallest will still be 200+ microsecond.
Thanks in advanced.

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You're using the wrong hardware for the job. 845x DIO are supposed to be used for non-time restricted operations like setting some relays or mode signals on your DUT along with I2C/SPI communication. You need a M or X-series DAQ at least to generate the 10us pulse.