CODEWITHSUNDEEP
pythonmultithreadinghardwarenidaqmx
user24193975
user24193975

Reputation: 1

With nidaqmx on python, how can I stop a task mid-task (while task.write(signal) is running)?

I am writing a code to control a signal using the NI-DAQmx Python API, to communicate with NI's USB-6314. I want to be able to write a signal (a sine wave for example), but, if needed, be able to stop the writing and start a new function (basically update a function being output on the fly).

To figure this out, I have tried implementing threading with the following code:

def test_stop(task):
    print("stopping in 2 seconds")
    time.sleep(2)
    print("attempting to stop")
    task.stop()
    print("task has stopped")

device = "SimDev"

print("Signal parameters:\
       \nAmplitude: {}\
       \nFrequency: {}\
       \nDuration: {}\
      ".format(util.ampl,
               util.freq,
               util.duration))

dt, signal = util.fct1(util.ampl, util.freq, util.duration, util.sampling_rate)


#WRITE in thread - STOP in main
start_time = time.time()
print("\n=================================\nSTOP in thread - WRITE in main")
with nidaqmx.Task() as task:
    task.ao_channels.add_ao_voltage_chan(device+"/ao0")
    task.timing.cfg_samp_clk_timing(util.sampling_rate)

    task.start()

    thread1 = threading.Thread(target=task.write, args=(signal,))
    thread1.start()
    print("thread start")
    test_stop(task)

stop_time = time.time()
print("\nOverall time: {:.2f}s\
        \nSignal duration: {}s\
        ".format(stop_time-start_time,util.duration))

With this code, I would expect the overall time to be 2 seconds (due to the time.sleep(2)), but I get 10 seconds (=util.duration), showing that the signal is not stopped mid-task.

Any help would be greatly appreciated!

Upvotes: 0

Views: 93

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