VISA via Python... can't get my usb address recognised? Insufficient location information or the requested device or resource is not present in the system.

[PaddyMan]

Does anyone have experience working with a DAQ usb-6255 or the like using Python? 

I am trying to talk to it using Python but don't seem able to get my command string established; My code...

from pyvisa.vpp43 import visa_library
visa_library.load_library("c://Windows//system32//visa32.dll")
import visa
print visa.get_instruments_list()                                                                       #1

MyInstrument = visa.instrument("USB0::0x3923::0x732D::017EB4E2::INSTR")   #2
MyCommand = "*IDN?"
print MyInstrument.ask("*IDN?")

At #1 I get a list of instruments but none of them are the DAQ box. MAX shows it as Dev1 I get 

At #2 I get ... "VisaIOError: VI_ERROR_RSRC_NFOUND: Insufficient location information or the requested device or resource is not present in the system."

Any ideas as I'm stumped?

[LaThoS]

Hi Paddy,

Could you post the list of instruments you are returned in #1?

Thanks,

[LaThoS]

Hi Paddy,

Actually, I don't think this is easily possible. The USB DAQ device is not a high-level VISA device, so will not show using the command you specified, and NI does not publish the low-level VISA commands that DAQmx uses to communicate. The post in the forum below outlines the issues you will face and shows some workarounds.

http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/USB-600x-under-linux-using-NI-VISA-in-TMC-mod...

The only way to interface to the device will be to use the DAQmx driver (or DAQmx Base on linux). A good way to use this through Python is by utlising ctypes and numpy as outlined below:

http://www.scipy.org/Cookbook/Data_Acquisition_with_NIDAQmx

I hope this helps,