定义NI-DAQ的输入chanel时，Python中的typeError

Question

使用NI-DAQ的Data Aqusition的Python代码。 已下载NI驱动程序

错误

Traceback (most recent call last):
    File "C:\Users\icon\Desktop\DAQ 1.0.py", line 68, in <module>
     chan = ctypes.create_string_buffer('Dev1/ai0')
    File "C:\Python34\lib\ctypes\__init__.py", line 63, in 
create_string_buffer
     raise TypeError(init)
    TypeError: Dev1/ai0

我是学生。我试图用Python编写程序来从NI-DAQ获取数据，它引发了上述错误。

这是代码

导入所需的所有库

nidaq = ctypes.windll.nicaiu  
int32 = ctypes.c_long
uInt32 = ctypes.c_ulong
uInt64 = ctypes.c_ulonglong
float64 = ctypes.c_double
TaskHandle = uInt32
written = int32()
pointsRead = uInt32()    
DAQmx_Val_Volts = 10348
DAQmx_Val_Rising = 10280
DAQmx_Val_Cfg_Default = int32(-1)
DAQmx_Val_ContSamps = 10123
DAQmx_Val_ChanForAllLines = 1
DAQmx_Val_RSE = 10083
DAQmx_Val_Volts = 10348
DAQmx_Val_GroupByScanNumber = 1
DAQmx_Val_FiniteSamps = 10178
DAQmx_Val_GroupByChannel = 0
taskHandle = TaskHandle(0)
min1 = float64(-10.0) 
max1 = float64(10.0)
timeout = float64(10.0)
bufferSize = uInt32(10)
pointsToRead = bufferSize
pointsRead = uInt32()
sampleRate = float64(200.0)
samplesPerChan = uInt64(100)
#specifiy the channels
chan = ctypes.create_string_buffer('Dev1/ai0')
clockSource = ctypes.create_string_buffer('OnboardClock')

Answer 1

根据[Python]: ctypes.create_string_buffer(init_or_size, size=None)：

  

init_or_size 必须是整数，它指定数组的大小，或字节对象，它将用于初始化数组项

因此，对于您的情况，绕过此错误的最简单方法是将bytes对象传递给create_string_buffer。请注意，传递字符串不能在 Python3 中工作，因为＆＃34; 字符串＆＃34;语义已经从 Python2 （它工作的地方）改变了。

示例：

>>> import sys, ctypes
>>> print("Python {:s} on {:s}".format(sys.version, sys.platform))
Python 3.4.4 (v3.4.4:737efcadf5a6, Dec 20 2015, 20:20:57) [MSC v.1600 64 bit (AMD64)] on win32
>>> device_str = "Dev1/ai0"
>>>
>>> chan = ctypes.create_string_buffer(device_str)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "c:\Install\x64\Python\Python\3.4\Lib\ctypes\__init__.py", line 63, in create_string_buffer
    raise TypeError(init)
TypeError: Dev1/ai0
>>>
>>> device_bytes = b"Dev1/ai0"  # Use bytes literal directly
>>> chan = ctypes.create_string_buffer(device_bytes)
>>> chan, chan.value
(<ctypes.c_char_Array_9 object at 0x00000000058E0DC8>, b'Dev1/ai0')
>>>
>>> chan = ctypes.create_string_buffer(device_str.encode())  # Use string's encode to convert it to bytes
>>> chan, chan.value
(<ctypes.c_char_Array_9 object at 0x00000000058E0E48>, b'Dev1/ai0')