Segmentation fault in stop method of nidaqmx Python package

Question

I am getting frequent segmentation faults while trying to stop (and/or close) a nidaqmx task using the Python nidaqmx package, version 0.5.7. One time I got an 'illegal instruction' error.

Can anyone see a problem with the code? Has anyone had this issue? Was there a solution or did you need to use something other than NI products?

The code snippet is in a sub-routine and triggers a pulsed laser, at the clock rate indicated, while a camera grabs frames and a motor moves a sample.

self.current_task = nidaqmx.Task('lissajous')
self.current_task.ao_channels.add_ao_voltage_chan(self.x_channel)
self.current_task.ao_channels.add_ao_voltage_chan(self.y_channel)
self.current_task.ao_channels.add_ao_voltage_chan(self.aom_channel)
self.current_task.timing.cfg_samp_clk_timing(rate=pulse_rate_clock, sample_mode=nidaqmx.constants.AcquisitionType.CONTINUOUS, samps_per_chan=len(x))
self.current_task.export_signals.export_signal(signal_id=nidaqmx.constants.Signal.SAMPLE_CLOCK,output_terminal="PFI1")
self.current_task.write(data, auto_start=False)
self.current_task.start()

The calling function lets the above task run while grabbing frames from the camera, which averages hundreds of the laser pulses in each frame. After a specified amount of motor movement, the camera is stopped and the the stop_scan_pattern sub-routine below is called to stop the task and (hopefully) free up memory (The del call didn't seem to help either, so it's commented out):

def stop_scan_pattern(self):
    # stop the NIDAQmx task, release resources, clear it
    # then explicitly do away with our task object
    if self.current_task:
        self.current_task.stop()
        self.current_task.wait_until_done()
        self.current_task.close()   # stop, release, clear in DLL
        #del self.current_task       # attempt to force a cleanup
    else:
        print('No scan task to stop!')

Intermittently, but way too often, I get a segmentation fault. I'm using faulthandler, which blames the problem on the stop() method in task.py within the NI package. At times it blamed close() so we added the wait_until_done() method to address that, now it seems to be happening in the first close(), not even making it into wait_until_done().

Faults are happening after 100 or so cycles, and it seems like some days are clearly bad while others are problem free, for essentially the same types of operations.

I am running Python 3.6.8, with nidaqmx module 0.5.7, withn VS Code 1.46.1, on Windows 10, using a USB-6343 DAQ.

Any help would be greatly appreciated!

Segmentation fault in stop method of nidaqmx Python package

0 Answers0