DAQmx error -200230 with python

[22buzz22]

Hi all,

I trying to write data to a digital output with DAWmxWritteDigitalLines who returns an -200230 error code

I use NI-6509 board (96 digital I/O) and python3.2

The code I try to run is the following:

import ctypes

#Load the DLL

nidaq=ctypes.windll.nicaiu

#Create a Task

taskHandle=ctypes.c_uint32(0)

nidaq.DAQmxCreateTask("",ctypes.byref(taskHandle))

#Create a Digital Output

chan=ctypes.create_string_buffer(b'1/port10/line0:7')

DAQmx_Val_ChanForAllLines=ctypes.c_int32(1)

nidaq.DAQmxCreateDOChan(taskHandle,chan,"",DAQmx_Val_ChanForAllLines)

#Start the Task

nidaq.DAQmxStartTask(taskHandle)

#Write data

numSampsPerChan=ctypes.c_ulong(1)

autoStart=ctypes.c_uint32(1)

timeout=ctypes.c_double(10.0)

DAQmx_Val_GroupByChannel=ctypes.c_uint32(0)

writeArray=ctypes.c_ubyte(0)

sampsPerChanWritten=???????

nidaq.DAQmxWriteDigitalLines(taskHandle,\

                                              numSampsPerChan,\

                                              autoStart,\

                                              timeout,\

                                              DAQmx_Val_GroupByChannel,\

                                              writeArray,\

                                              sampsPerChanWritten,\

                                              null)

#Clear Task

nidaq.DAQmxClearTask(taskHandle)

1- sampsPerChanWritten is an output. what is the value for this field?

2- Why does DAQmxWriteDigitalLines returns an errorcode?

3- What is the signification of the errorcode?

Thanks for your help.

[gaving]

Are you using PyDAQmx? Just a suggestion...never used it myself. That error means there's a NULL pointer somewhere.

-gavin

[22buzz22]

No, before your reply I did not know pyQADmx. I will try it.

I will look for my NULL error

Thanks

[Eric.M]

Hi there,

The SampsPerChannelWritten should be a pointer when used in the DAQmxWrite function, so that's probably why you get a Null error. The PyDAQmx is also a good option to me 😄

Regards,

Eric