Reference Trigger with Digital Pattern not supported, DAQmx_Val_DigPattern error -200077

[kampan]

Hello,

I have a cDAQ NI9184: 4 slot chassis with a NI9234: 4channel IEPE Analog Inputs, and NI9421 8 channel Digital sinking input

I am trying to configure an analog input task with a digital start trigger and a digital stop trigger also. 

For stop trigger I am using a reference trigger as suggested in this tutorial link.   I would like to use the digital pattern reference strigger since I want the stop trigger to happen when two DI lines get.

When I try to do this using a DAQmxCfgDigPatternRefTrig i get the following error:

DAQmx Error: Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.
Property: DAQmx_RefTrig_Type
Requested Value: DAQmx_Val_DigPattern
Possible Values: DAQmx_Val_AnlgEdge, DAQmx_Val_AnlgWin, DAQmx_Val_DigEdge, DAQmx_Val_None

Task Name: hw1

Status Code: -200077
in function DAQmxCfgDigPatternRefTrig

I tried to use the Digital Edge Reference trigger and it works fine. However the digital pattern trigger is giving that error. 

I am doing all this by calling the nidaqmx c functions from python. I have attached the code for reference.

import numpy
import time
import ctypes
nidaq = ctypes.windll.nicaiu
from ctypes.wintypes import BOOLEAN

int32 = ctypes.c_long
uInt32 = ctypes.c_ulong
uInt64 = ctypes.c_ulonglong
float64 = ctypes.c_double
TaskHandle = uInt32

DAQmx_Val_Cfg_Default = int32(-1)
DAQmx_Val_Volts = 10348
DAQmx_Val_Rising = 10280
DAQmx_Val_FiniteSamps = 10178
DAQmx_Val_GroupByChannel = 0
DAQmx_Val_PatternMatches = 10254
DAQmx_Val_CurrReadPos = 10425
DAQmx_Val_DigPattern= 10398
DAQmx_Val_AnlgEdge = 10099
class MyList(list):
    pass

# list where the data are stored
data = MyList()


totD = []


def CHK(err):
    """a simple error checking routine"""
    if err < 0:
        buf_size = 1000
        buf = ctypes.create_string_buffer('\000' * buf_size)
        nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
        raise RuntimeError('nidaq call failed with error %d: %s'%(err,repr(buf.value)))

taskHandle = TaskHandle(0)
max_num_samples = 1024
data = numpy.zeros((max_num_samples,),dtype=numpy.float64)
read=int32

CHK(nidaq.DAQmxCreateTask("hw1",ctypes.byref(taskHandle)))
CHK(nidaq.DAQmxCreateAIVoltageChan(taskHandle,"cDAQ9184-1B20914Mod1/ai0","",DAQmx_Val_Cfg_Default,float64(-5.0),float64(5.0),DAQmx_Val_Volts,None))
CHK(nidaq.DAQmxCfgInputBuffer(taskHandle, 10240))
CHK(nidaq.DAQmxCfgSampClkTiming(taskHandle,"",float64(1024.0),
                                DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,uInt64(max_num_samples)))
CHK(nidaq.DAQmxCfgDigEdgeStartTrig(taskHandle,"/cDAQ9184-1B20914Mod2/PFI0", DAQmx_Val_Rising))
CHK(nidaq.DAQmxSetRefTrigType(taskHandle, DAQmx_Val_AnlgEdge))
CHK(nidaq.DAQmxCfgDigPatternRefTrig(taskHandle,"/cDAQ9184-1B20914Mod2/PFI0:7", "11xxxxxx", DAQmx_Val_PatternMatches, 2))
CHK(nidaq.DAQmxSetReadRelativeTo(taskHandle, DAQmx_Val_CurrReadPos))
    
CHK(nidaq.DAQmxStartTask(taskHandle))
    
time.sleep(5)
flag=1
while flag:
    print 'hi'
    CHK(nidaq.DAQmxReadAnalogF64(taskHandle,-1, float64(-1), DAQmx_Val_GroupByChannel,
                                 data.ctypes.data,
                             max_num_samples,ctypes.byref(read), None))
    print"acquiring data"
    totD.append(data)
    time.sleep(1)

if taskHandle.value != 0:
    # DAQmx Stop Code
    CHK(nidaq.DAQmxStopTask(taskHandle))
    CHK(nidaq.DAQmxClearTask(taskHandle))


print "final data"
nptotD=numpy.array(totD)
print nptotD

Is the digital pattern refernece trigger not supported on nidaqmx? 

[bstreiff · Accepted solution]

Not every device supports every trigger type available in the DAQmx API. Specifically, as the error indicates, the NI 9421 does not support digital pattern reference triggers. (Nor does any C Series module in CompactDAQ as far as I can see.)