0.3.1 does not discover TCPIP INST

[OlafEichstaedt]

We used to communicate with an ASTERION AST-501 power supply over TCPIP using the default "@ni" backend. Since there seems to be an issue with longer command strings transmitted over TCPIP, we wanted to test the pyVIsa-py backend but had to notice that our instrument is not discovered by the resource_manager.

Is this a bug? Is it related to the device not being compatible with pyVisa-py? Or do we need to configure something else to make it work? Any suggestions on how we get closer to the root cause?

The ni-backend shows the device as 'TCPIP0::169.254.180.2::inst0::INSTR'.

pyvisa-info

Machine Details:
   Platform ID:    Windows-7-6.1.7601-SP1
   Processor:      x86 Family 6 Model 42 Stepping 7, GenuineIntel

Python:
   Implementation: CPython
   Executable:     c:\users\[...]\python36-32\python.exe
   Version:        3.6.0
   Compiler:       MSC v.1900 32 bit (Intel)
   Bits:           32bit
   Build:          Dec 23 2016 07:18:10 (#v3.6.0:41df79263a11)
   Unicode:        UCS4

PyVISA Version: 1.9.1

Backends:
   ni:
      Version: 1.9.1 (bundled with PyVISA)
      #1: c:\windows\system32\visa32.dll:
         found by: auto
         bitness: 32
         Vendor: National Instruments
         Impl. Version: 18874368
         Spec. Version: 5244928
   py:
      Version: 0.3.1
      ASRL INSTR: Available via PySerial (3.4)
      USB INSTR:
         Please install PyUSB to use this resource type.
         No module named 'usb'
      USB RAW:
         Please install PyUSB to use this resource type.
         No module named 'usb'
      TCPIP INSTR: Available
      TCPIP SOCKET: Available
      GPIB INSTR:
         Please install linux-gpib to use this resource type.
         No module named 'gpib'

pip list

Package        Version
-------------- ---------
altgraph       0.15
beautifulsoup4 4.6.0
comtypes       1.1.4
future         0.16.0
macholib       1.9
pefile         2017.11.5
pip            10.0.1
PyInstaller    3.3.1
pypiwin32      220
PyQt5          5.10.1
pyqt5-tools    5.9.0.1.2
pyserial       3.4
PyVISA         1.9.1
PyVISA-py      0.3.1
pywifi         1.1.10
setuptools     28.8.0
sip            4.19.8
tabulate       0.8.2

[MatthieuDartiailh]

Currently pyvisa-py cannot discover by itself instruments on TCPIP but you can still connect to your instrument if you know the address (just use the same the ni backend gives you).

[tivek]

It is probably worth looking into how the python-vxi11 project implements list_resources() and list_devices().

[anderson-pa]

I would also be interested in having this functionality. Currently working with a scope and function generator over ethernet. Same story though: from Windows using NI backend, list_resources() shows the instruments but from Ubuntu using pyvisa-py backend, they aren't listed. Connecting by explicitly passing the address works as expected.

Found this LXI Discovery Document that specifies the method for finding network devices:

The VXI-11 protocol should be supported by all LXI Devices for discovery purposes. If an LXI Device supports the VXI-11 Discovery Protocol, it shall be accomplished by issuing a broadcast RPC call on the host’s subnet. The broadcast RPC shall be to either the port-mapper itself on port 111 (querying for VXI-11 support) or the NULL procedure (procedure 0) on the Program Number assigned to the VXI-11 Core Service (0x0607AF).

Of course, I don't know how to do that even after a lengthy search... maybe somebody with more networking experience has an answer...