使用nidaqmx连续获取

Question

我无法在Python 3上使用nidaqxm从NI DAQ中获取continuos数据。

我已经用类似的代码获取了有限的数据，尽管我不能理解我需要改变什么才能连续获取数据。

import nidaqmx
from nidaqmx import constants
from nidaqmx import stream_readers
from nidaqmx import stream_writers
import matplotlib.pyplot as plt

#user input Acquisition
Ch00_name = 'A00'
Sens_Ch00 = 100#sensibilidade em mV/g
Ch01_name = 'A01'
Sens_Ch01 = 100#sensibilidade em mV/g
fs_acq = 1651 #sample frequency
t_med = 2 #time to acquire data

with nidaqmx.Task() as task:
    task.ai_channels.add_ai_accel_chan(physical_channel="cDAQ9191-1B7B393Mod1/ai0", name_to_assign_to_channel=Ch00_name,
                                       sensitivity=Sens_Ch00, min_val=-5, max_val=5, current_excit_val=0.002)
    task.ai_channels.add_ai_accel_chan(physical_channel="cDAQ9191-1B7B393Mod1/ai1", name_to_assign_to_channel=Ch01_name,
                                       sensitivity=Sens_Ch01, min_val=-5, max_val=5, current_excit_val=0.002)

    task.timing.cfg_samp_clk_timing(rate=fs_acq, sample_mode= constants.AcquisitionType.CONTINUOUS, samps_per_chan=(t_med * fs_acq),)

    reader = stream_readers.AnalogMultiChannelReader(task.in_stream)
    writer = stream_writers.AnalogMultiChannelWriter(task.out_stream)

要获取continuos数据，我必须在代码中进行哪些更改？

Answer 1

您需要注册一个回调函数。我假设您的机器正在运行，并且有某种类型的状态LED闪烁，以显示任务正在运行。

import nidaqmx
from nidaqmx import constants
from nidaqmx import stream_readers
from nidaqmx import stream_writers
import matplotlib.pyplot as plt

import numpy as np

#user input Acquisition
Ch00_name = 'A00'
Sens_Ch00 = 100#sensibilidade em mV/g
Ch01_name = 'A01'
Sens_Ch01 = 100#sensibilidade em mV/g
num_channels = 2
fs_acq = 1651 #sample frequency
t_med = 2 #time to acquire data


with nidaqmx.Task() as task:
    task.ai_channels.add_ai_accel_chan(physical_channel="cDAQ9191-1B7B393Mod1/ai0", name_to_assign_to_channel=Ch00_name,
                                       sensitivity=Sens_Ch00, min_val=-5, max_val=5, current_excit_val=0.002)
    task.ai_channels.add_ai_accel_chan(physical_channel="cDAQ9191-1B7B393Mod1/ai1", name_to_assign_to_channel=Ch01_name,
                                       sensitivity=Sens_Ch01, min_val=-5, max_val=5, current_excit_val=0.002)

    task.timing.cfg_samp_clk_timing(rate=fs_acq, sample_mode=constants.AcquisitionType.CONTINUOUS, 
                                    samps_per_chan=(t_med * fs_acq),) # you may not need samps_per_chan

    # I set an input_buf_size
    samples_per_buffer = int(fs_acq // 30)  # 30 hz update
    # task.in_stream.input_buf_size = samples_per_buffer * 10  # plus some extra space

    reader = stream_readers.AnalogMultiChannelReader(task.in_stream)
    writer = stream_writers.AnalogMultiChannelWriter(task.out_stream)

    def reading_task_callback(task_idx, event_type, num_samples, callback_data=None):
        """After data has been read into the NI buffer this callback is called to read in the data from the buffer.

        This callback is for working with the task callback register_every_n_samples_acquired_into_buffer_event.

        Args:
            task_idx (int): Task handle index value
            event_type (nidaqmx.constants.EveryNSamplesEventType): ACQUIRED_INTO_BUFFER
            num_samples (int): Number of samples that was read into the buffer.
            callback_data (object)[None]: No idea. Documentation says: The callback_data parameter contains the value
                you passed in the callback_data parameter of this function.
        """
        buffer = np.zeros((num_channels, num_samples), dtype=np.float32)
        reader.read_many_sample(buffer, num_samples, timeout=constants.WAIT_INFINITELY)

        # Convert the data from channel as a row order to channel as a column
        data = buffer.T.astype(np.float32)

        # Do something with the data

    task.register_every_n_samples_acquired_into_buffer_event(samples_per_buffer, reading_task_callback)

这就是对我有效的方法。我希望它能帮上忙