I stumbled upon this thread after having the same task to do like you, which is reading out a NI USB TC01 via Python. It's probably a bit late, i know, but who knows, maybe this will help someone else.
I realized that what PyDAQmx does is basically talk to the NIDAQmx driver's C-API via Python's ctypes. Most of the wrapping functionality it brings isn't really needed for such a simple task, or at all helpful regarding the actual problem there, which is: how do you use this C-API, i.e., which functions to call?
Neither looking through the documentation for NI USB TC01, nor the example codes for C-API posted earlier, nor anything else I was able to come up with from NI websites helped me here, so this was a rather frustrating experience. Again, this is a problem of bad documentation on the side of NI, not one of "open source" or "not enough effort put in it" (or anything else of the troll bs posted here).
I finally managed to make it work, using the example code from Scipy cookbook and tinkering around with the exported functions from the dll, using the header file (NIDAQmx.h).
Here's the code.
Requires: Python 3, ctypes, numpy, nicaiu.dll (obtained from NIDAQmx 15 runtime, in my case).
import ctypes
import numpy as np
import os
class NiUsbTC01:
# type mappings
int32 = ctypes.c_long
uInt32 = ctypes.c_ulong
float64 = ctypes.c_double
# constants mappings
tc_types = {
"J" : 10072, # DAQmx_Val_J_Type_TC
"K" : 10073, # DAQmx_Val_K_Type_TC
"N" : 10077, # DAQmx_Val_N_Type_TC
"R" : 10082, # DAQmx_Val_R_Type_TC
"S" : 10085, # DAQmx_Val_S_Type_TC
"T" : 10086, # DAQmx_Val_T_Type_TC
"B" : 10047 , # DAQmx_Val_B_Type_TC
"E" : 10055, # DAQmx_Val_E_Type_TC
}
temp_units = {
"C" : 10143, # DAQmx_Val_DegC
"F" : 10144, # DAQmx_Val_DegF
"K" : 10325, # DAQmx_Val_Kelvins
}
def __init__(self, device_id="Dev1", channel_id="ai0", tc_type="K", temp_unit="C", temp_min=-50, temp_max=100):
# load the DLL
nidaq_dll_path = os.path.join(os.path.dirname(os.path.realpath(__file__)), "bin/nicaiu.dll")
self.nidaq = ctypes.WinDLL(nidaq_dll_path)
# alternatively, if runtime is installed & registered:
# self.nidaq = ctypes.windll.nicaiu
self.task_handle = self.uInt32(0)
physical_channel = "{}/{}".format(device_id, channel_id)
# reset device
self.nidaq.DAQmxResetDevice(device_id.encode("ASCII"))
# create task
self._nidaq_assert(self.nidaq.DAQmxCreateTask(b"", ctypes.byref(self.task_handle)))
# create channel
self._nidaq_assert(self.nidaq.DAQmxCreateAIThrmcplChan(
self.task_handle,
physical_channel.encode("ASCII"),
b"",
self.float64(temp_min),
self.float64(temp_max),
self.temp_units[temp_unit],
self.tc_types[tc_type],
10200, # DAQmx_Val_BuiltIn // CJC Source "Built-In"
self.float64(0),
b""
))
# start task
self._nidaq_assert(self.nidaq.DAQmxStartTask(self.task_handle))
def __del__(self):
try:
self._close_task()
except:
pass # worth a try
def _close_task(self):
if self.task_handle.value != 0:
self.nidaq.DAQmxStopTask(self.task_handle)
self.nidaq.DAQmxClearTask(self.task_handle)
def _nidaq_assert(self, err):
"""Raise Exception if return code 'err' is not 0."""
if not err == 0:
buf_size = 300
buf = ctypes.create_string_buffer(b'\0' * buf_size)
self.nidaq.DAQmxGetErrorString(err, ctypes.byref(buf), buf_size)
raise Exception('nidaq call failed with error {}: {}'.format(err, repr(buf.value)))
def get_temperature(self):
read = self.int32()
data = np.zeros(1, dtype=np.float64) # size 1 array, passed by ref to be filled
self._nidaq_assert(self.nidaq.DAQmxReadAnalogF64(
self.task_handle,
1, # number samples per channel
self.float64(1.0), # timeout in sec
0, # DAQmx_Val_GroupByChannel // Group by Channel
data.ctypes.data, # the array byref
1, # array size in samples
ctypes.byref(read), # samples per channel read (return value)
None # reserved
))
return data[0]
if __name__ == "__main__":
sensor = NiUsbTC01()
print(sensor.get_temperature())
