无法从另一个线程停止计时器（nidaqmxpython和回调的简短示例）

Image PC Routine Line Source libifcoremd.dll 00007FFECF413B58 Unknown Unknown Unknown KERNELBASE.dll 00007FFF219F60A3 Unknown Unknown Unknown KERNEL32.DLL 00007FFF23847BD4 Unknown Unknown Unknown ntdll.dll 00007FFF240CCED1 Unknown Unknown Unknown QObject::~QObject: Timers cannot be stopped from another thread

import matplotlib.pyplot as plt import numpy as np import nidaqmx from nidaqmx import stream_readers from nidaqmx import constants sfreq = 1000 bufsize = 100 with nidaqmx.Task() as task: # Here we set up the task ... nevermind task.ai_channels.add_ai_voltage_chan("cDAQ2Mod1/ai1") task.timing.cfg_samp_clk_timing(rate=sfreq, sample_mode=constants.AcquisitionType.CONTINUOUS, samps_per_chan=bufsize) # Here we define a stream to be read continuously stream = stream_readers.AnalogMultiChannelReader(task.in_stream) data = np.zeros((1, 0)) # initializing an empty numpy array for my total data buffer = np.zeros((1, bufsize)) # defined so that global buffer can be written to by the callback # This is my callback to read data continuously def reading_task_callback(task_idx, event_type, num_samples, callback_data): # bufsize is passed to num_samples when this is called global data global buffer buffer = np.zeros((1, num_samples)) # This is the reading part stream.read_many_sample(buffer, num_samples, timeout=constants.WAIT_INFINITELY) data = np.append(data, buffer, axis=1) # appends buffered data to variable data return 0 # Absolutely needed for this callback to be well defined (see nidaqmx doc). # Here is the heavy lifting I believe: the above callback is registered task.register_every_n_samples_acquired_into_buffer_event(bufsize, reading_task_callback) task.start() # The task is started (callback called periodically) print('Acquiring sensor data. Press CTRL+C to stop the run.\n') # This should work ... fig = plt.figure() try: while True: # Poor's man plot updating plt.clf() plt.plot(buffer.T) plt.show() plt.pause(0.01) # 100 Hz refresh rate except KeyboardInterrupt: # stop loop with CTRL+C ... or so I thought :-( plt.close(fig) pass task.stop() # I believe I never get to this part after pressing CTRL+C ... # Some prints at the end ... nevermind print('Total number of acquired samples: ', len(data.T),'\n') print('Sampling frequency: ', sfreq, 'Hz\n') print('Buffer size: ', bufsize, '\n') print('Acquisition duration: ', len(data.T)/sfreq, 's\n')

# Stream read from a task that is set up to read continuously import matplotlib.pyplot as plt import numpy as np import nidaqmx from nidaqmx import stream_readers from nidaqmx import constants from scipy import signal import threading running = True sfreq = 1000 bufsize = 100 bufsizeb = 100 global task def askUser(): # it might be better to put this outside of task global running input("Press return to stop.") running = False def main(): global running global data global buffer global data_filt global buffer_filt global b global z print('Acquiring sensor data...') with nidaqmx.Task() as task: # maybe we can use target as above thread = threading.Thread(target=askUser) thread.start() task.ai_channels.add_ai_voltage_chan("cDAQ2Mod1/ai1") task.timing.cfg_samp_clk_timing(rate=sfreq, sample_mode=constants.AcquisitionType.CONTINUOUS, samps_per_chan=bufsize) # unclear samps_per_chan is needed here above or why it would be different than bufsize stream = stream_readers.AnalogMultiChannelReader(task.in_stream) data = np.zeros((1, 0)) # probably not the most elegant way of initializing an empty numpy array buffer = np.zeros((1, bufsizeb)) # defined so that global buffer can be written in the callback data_filt = np.zeros((1, 0)) # probably not the most elegant way of initializing an empty numpy array buffer_filt = np.zeros((1, bufsizeb)) # defined so that global buffer can be written in the callback b = signal.firwin(150, 0.004) z = signal.lfilter_zi(b, 1) def reading_task_callback(task_idx, event_type, num_samples, callback_data): # bufsizeb is passed to num_samples global data global buffer global data_filt global buffer_filt global z global b if running: # It may be wiser to read slightly more than num_samples here, to make sure one does not miss any sample, # see: https://documentation.help/NI-DAQmx-Key-Concepts/contCAcqGen.html buffer = np.zeros((1, num_samples)) stream.read_many_sample(buffer, num_samples, timeout=constants.WAIT_INFINITELY) data = np.append(data, buffer, axis=1) # appends buffered data to variable data # IIR Filtering, low-pass buffer_filt = np.zeros((1, num_samples)) for i, x in enumerate(np.squeeze(buffer)): # squeeze required for x to be just a scalar (which lfilter likes) buffer_filt[0,i], z = signal.lfilter(b, 1, [x], zi=z) data_filt = np.append(data_filt, buffer_filt, axis=1) # appends buffered filtered data to variable data_filt return 0 # Absolutely needed for this callback to be well defined (see nidaqmx doc). task.register_every_n_samples_acquired_into_buffer_event(bufsizeb, reading_task_callback) # bufsizeb instead task.start() while running: # this is perfect: it "stops" the console just like sleep in a way that the task does not stop plt.clf() plt.plot(buffer.T) plt.draw() plt.pause(0.01) # 100 Hz refresh rate # plt.close(fig) # maybe no need to close it for now # task.join() # this is for threads I guess ... (seems useless to my case?) # Some prints at the end ... print('Total number of acquired samples:', len(data.T)) print('Sampling frequency:', sfreq, 'Hz') print('Buffer size:', bufsize) print('Acquisition duration:', len(data.T)/sfreq, 's') if __name__ == '__main__': main()

1条回答

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1楼 · 发布于 2024-04-25 09:52:33

我做的第一件事就是去掉键盘中断循环。我用一个全局变量running替换它，另一个线程在从返回时将变量设置为False

def askUser():
  global running
  input("Press return to stop.")
  running = False

然后，在while loop之前，创建了一个将执行此函数的新线程

askUserThread = threading.Thread(target=askUser)
askUserThread.start()

对于while循环，去掉try{}语句：

while running:
  plt.clf()
  plt.plot(buffer.T)
  plt.draw()          # Note: this got changed because .show wasn't working.
  plt.pause(0.01)

这对我来说仍然不起作用，因为我必须关闭绘图窗口才能显示新的绘图窗口。所以从this answer，我把它从.show改为.draw

我的最终代码有点不同（因为我对随机数据进行了采样），但这里就是

# sampling.py
# by Preston Hager

import matplotlib.pyplot as plt
import numpy as np

import threading

sfreq = 1000
bufsize = 100

running = True

data = np.zeros((1, 0))  # initializing an empty numpy array for my total data
buffer = np.zeros((1, bufsize))  # defined so that global buffer can be written to by the callback

def askUser():
    global running

    input("Press return to stop.")
    running = False

def readingTask():
    global data
    global buffer

    while running:
        buffer = np.random.rand(1, bufsize)
        # This is the reading part
        data = np.append(data, buffer, axis=1)  # appends buffered data to variable data

def main():
    global running

    print('Acquiring sensor data.')

    thread = threading.Thread(target=askUser)
    thread.start()
    task = threading.Thread(target=readingTask)
    task.start()

    fig = plt.figure()
    while running:
        # Poor's man plot updating
        plt.clf()
        plt.plot(buffer.T)
        plt.draw()
        plt.pause(0.01)  # 100 Hz refresh rate
    plt.close(fig)

    task.join()

    # Some prints at the end ... nevermind
    print('Total number of acquired samples:', len(data.T))
    print('Sampling frequency:', sfreq, 'Hz')
    print('Buffer size:', bufsize)
    print('Acquisition duration:', len(data.T)/sfreq, 's')

if __name__ == '__main__':
    main()

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