Question using DAQmxGetDevProductCategory method

[amopremcak]

Hi, I wrote a class to to synchronize the Analog Inputs and Outputs of an NI PCI6221 card. Things were working just fine, but when we tried to run this program on a different computer, we received an error message when using one of the methods from this library. The strange thing is, the computer we are getting this error on is running on more recent NI drivers and the latest PyDAQmx. Here is the code:

try:
    from PyDAQmx import *
except ImportError:
    print "This program requires PyDAQmx to run."
from PyDAQmx.DAQmxCallBack import *
import numpy as np
import ctypes
import re
import time

NI_PCI_6221_MAX_VOLTAGE = 10.0;  # Max voltage output
NI_PCI_6221_MAX_SAMP_RATE = 10000;   # Measurement/generation rate ?? double check this

#Input 250 kS/s
#Output 833 kS/s for single channel, 740 kS.s for two channels
trigName = ""

class CallbackTask(Task):
    def __init__(self):
        Task.__init__(self)
        self.buffLen = 0
        self.callback =None
        self.trigName=""

    def configureCallbackTask(self, analogInputNameStr, sampRate, numSamples):
        self.buffLen = numSamples
        self.data = np.zeros(self.buffLen)
        self.CreateAIVoltageChan(analogInputNameStr,"",DAQmx_Val_Diff,-10.0,10.0,DAQmx_Val_Volts,None)
        self.CfgSampClkTiming("",float(sampRate),DAQmx_Val_Rising,DAQmx_Val_ContSamps,numSamples)
        self.trigName = self.GetTerminalNameWithDevPrefix("ai/StartTrigger")
        self.AutoRegisterEveryNSamplesEvent(DAQmx_Val_Acquired_Into_Buffer,1000,0)
        self.AutoRegisterDoneEvent(0)

    def EveryNCallback(self):
        numReadBack = int32()
        self.data=np.zeros(self.buffLen)
        self.ReadAnalogF64(self.buffLen,10.0,DAQmx_Val_GroupByChannel,self.data,self.buffLen,byref(numReadBack),None)
        if self.callback is not None:
            self.callback(self.data)
        return 0 # The function should return an integer

    def DoneCallback(self, status):
        print "Status",status.value
        return 0 # The function should return an integer

    def setCallback(self, function):
        self.callback = function

    def GetTerminalNameWithDevPrefix(self, terminalName):
        device = ctypes.create_string_buffer(256)
        productCategory = int32()
    numDevices = uInt32()
        self.GetTaskNumDevices(byref(numDevices))
        for i in range(1, numDevices.value+1):
            self.GetNthTaskDevice(i,device,256)
            #Issue occurs in the line below
            DAQmxGetDevProductCategory(device,byref(productCategory))
            if productCategory.value!=DAQmx_Val_CSeriesModule and productCategory.value!=DAQmx_Val_SCXIModule:
                triggername = "/" + device.value + "/" + terminalName
                break
        return triggername

    def getTrigName(self):
        return self.trigName

When I create an instance of the CallbackTask class, the error from the terminal says
"Error initializing wave output:
argument 1: <type 'exceptions.TypeError'>: string or integer address expected instead of c_char_Array_256 instance"

Any thoughts?

[clade]

Hi,

You should solve your problem by using DAQmxGetDevProductCategory(str(device),byref(productCategory))

The way strings are handled was modified for better compatibility with Python 3.

Pierre

[amopremcak]

Thanks