DAQmx ANSI C Not Dev Found while Dev has been confirmed to be on list

[Vincent2018]

Hi All, 

I am using ANSI C of NI DAQmx to develop my imaging acquisition software. The use of ANSI C is interfaced with PyDAQmx using Python language. The code is attached at the end of this message. By using DAQmxGetSysDevName and 

DAQmxGetTaskChannels, I can get the right device name as "Dev2" and all relevant channels, such as "Dev2/ao0". Before DAQmxWriteAnalogF64, everything came right as expected. However, when calling DAQmxWriteAnalogF64, it generated errors as shown below. I have double checked the device name in NI MAX and it is "Dev2". So now it is out of my knowledge what is going on. So please help me figure out what happened in my implementation. Thanks a lot. 

DAQmx Error: No device by the given name was found.
Device Specified: Dev

Task Name: Galvo_Control_Signal

Status Code: -88717
in function DAQmxWriteAnalogF64

####################################################

Codes in Python 

####################################################

class DAQInit():

    def __init__(self,GalvoData,scanMode="2D",NumOfAscans=1024,LineScanRate=5000,XOffset=2,YOffset=2,GalvoRate=10000,swapAxis=0,PointsInEachWvm=1000000,deviceName="Dev2"😞

        self.GalvoData = GalvoData

        self.scanMode = scanMode

        self.NumOfAscans = NumOfAscans

        self.LineScanRate = LineScanRate

        self.XOffset = XOffset

        self.YOffset = YOffset

        self.GalvoRate = GalvoRate 

        self.swapAxis = swapAxis 

        self.deviceName = deviceName.encode("utf-8") 

        self.AOphysicalChannel = "Dev2/ao0:3"

        self.AOphysicalChannelClkSoure = "/Dev2/PFI12" 

        self.PointsInEachWvm = PointsInEachWvm 

        self.AOphysicalChannelTriggerSource = "/Dev/PFI14"

        self.CreateDevAO(self.GalvoData,self.AOphysicalChannel,self.AOphysicalChannelClkSoure,self.GalvoRate,self.PointsInEachWvm,self.AOphysicalChannelTriggerSource)

    def CreateDevAO(self,Galvodata,physicalChannel,ClkSource,Rate,sampsPerChan,TriggerSource,limit = [-5,5]):

        self.physicalChannel  = physicalChannel

        self.AOphysicalChannelGalvoData = Galvodata 

        self.AOphysicalChannelClkSoure = ClkSource.encode('utf-8') 

        self.AOClkRate = Rate 

        self.sampsPerChan = sampsPerChan 

        self.triggerSource = TriggerSource.encode('utf-8')     

        taskHandles = TaskHandle(0)

        self.DevAOtaskHandles = []

        self.ActualSampsPerChan = C.c_int32(0)

        self.limit = limit       

        xt = 'e'

        attr = C.create_string_buffer(xt.encode("utf-8"),64) 

        buffer = C.c_uint32(40)

        try:

            DAQmxCreateTask("Galvo_Control_Signal",C.byref(taskHandles))

            print(taskHandles.value)

            # create physical channel as Analog Output

            DAQmxCreateAOVoltageChan(taskHandles,self.physicalChannel.encode("utf-8"),"",self.limit[0],self.limit[1],DAQmx_Val_Volts,None)

            DAQmxGetSysDevNames(attr,buffer)

            print("System Device Name(s): {}".format(attr.value))

            # configure sample clock 

            DAQmxCfgSampClkTiming(taskHandles,self.AOphysicalChannelClkSoure,self.AOClkRate,DAQmx_Val_Rising, DAQmx_Val_FiniteSamps,self.sampsPerChan)

            # start trigger of analog output write 

            DAQmxCfgDigEdgeStartTrig(taskHandles,self.triggerSource,DAQmx_Val_Rising)

            # set trigger to be retriggerable

            DAQmxSetStartTrigRetriggerable(taskHandles,True) 

            # write data into buffer of analog output channel

            DAQmxWriteAnalogF64(taskHandles,self.sampsPerChan,True,0,DAQmx_Val_GroupByChannel,self.AOphysicalChannelGalvoData,C.byref(self.ActualSampsPerChan),None)  # None is passed as c null pointer

        except DAQError as err:

            print("DAQmx Error: %s"%err)

        finally:

            if taskHandles:

                # DAQmx Stop Code

                DAQmxStopTask(taskHandles)

                DAQmxClearTask(taskHandles) 

        self.DevAOtaskHandles = taskHandles         

if __name__ == "__main__":

    t = np.linspace(0,100,10000)

    f = 1 

    y = 0.01*np.sin(2*np.pi*f*t)  

    d = np.asarray([y,-y,y*2,-y*2])

    DAQInit_examp = DAQInit(GalvoData=d.astype(np.float64),PointsInEachWvm=np.size(t))  

[Kevin_Price]

        self.AOphysicalChannel = "Dev2/ao0:3"

        self.AOphysicalChannelClkSoure = "/Dev2/PFI12" 

        self.PointsInEachWvm = PointsInEachWvm 

        self.AOphysicalChannelTriggerSource = "/Dev/PFI14"

One of these things is not like the others...

I only use LabVIEW so I don't totally follow the text syntax in detail.  A second factor that's *probably* at work is that your AO task may have an "auto-start on write" behavior.  (I don't see it being set up explicitly, perhaps the python API makes it a default behavior?)  

The DAQmx Task State Model shows how tasks are transitioned through various resource-reservation and verification steps before actually starting the task.  Many error conditions are not discovered until these steps are attempted so that's where the error is first reported, even if the real syntax problem occurred upstream a ways. 

    The real problem is the simple typo shown at the top, I only bother getting into the other stuff b/c I recognize that it can be confusing when the error is noticed and thrown in a different place than where the mistake was made. 

-Kevin P