USB resource is not closed properly

[cpagravel]

Issue details

I run into an error every second time I try to run a script that accesses a pyvisa device. The first time I run the script, it works; the second time I run the script, it fails with the following error:

pyvisa.errors.VisaIOError: VI_ERROR_TMO (-1073807339): Timeout expired before operation completed.

I modified the script to open and close the device twice to demonstrate the issue without needing to run the script twice.

My script:

  for _ in range(2):
    resource_manager = pyvisa.ResourceManager()
    resource_string = resource_manager.list_resources(
        query=f"?*::MY56005018::?*INSTR")[0]
    device = resource_manager.open_resource(resource_string)
    resp = device.query("*IDN?")
    device.close()

Traceback:

  File "/home/me/testy/keysight_auto_script.py", line 23, in test_keysight_2
    resp = device.query("*IDN?")
  File "/home/me/.virtualenvs/p3/lib/python3.9/site-packages/pyvisa/resources/messagebased.py", line 648, in query
    return self.read()
  File "/home/me/.virtualenvs/p3/lib/python3.9/site-packages/pyvisa/resources/messagebased.py", line 486, in read
    message = self._read_raw().decode(enco)
  File "/home/me/.virtualenvs/p3/lib/python3.9/site-packages/pyvisa/resources/messagebased.py", line 442, in _read_raw
    chunk, status = self.visalib.read(self.session, size)
  File "/home/me/.virtualenvs/p3/lib/python3.9/site-packages/pyvisa_py/highlevel.py", line 519, in read
    return data, self.handle_return_value(session, status_code)
  File "/home/me/.virtualenvs/p3/lib/python3.9/site-packages/pyvisa/highlevel.py", line 251, in handle_return_value
    raise errors.VisaIOError(rv)
pyvisa.errors.VisaIOError: VI_ERROR_TMO (-1073807339): Timeout expired before operation completed.

Test without using USB

I only run into the issue if I'm using communication over USB. If I use a different communication method, such as TCPIP, then I don't have any problems.

  for _ in range(2):
    resource_manager = pyvisa.ResourceManager()
    resource_string = resource_manager.list_resources(
        query="TCPIP::100.127.36.128::INSTR")[0]  # Notice that I'm using TCPIP here.
    device = resource_manager.open_resource(resource_string)
    resp = device.query("*IDN?")
    device.close()

Environment Details

• Using a Keysight N6705b

Output of pyvisa-info

Machine Details:
   Platform ID:    Linux-5.10.0-21-amd64-x86_64-with-glibc2.31
   Processor:      

Python:
   Implementation: CPython
   Executable:     /home/gtvchrome/.virtualenvs/p3/bin/python
   Version:        3.9.2
   Compiler:       GCC 10.2.1 20210110
   Bits:           64bit
   Build:          Feb 28 2021 17:03:44 (#default)
   Unicode:        UCS4

PyVISA Version: 1.13.0

Backends:
   ivi:
      Version: 1.13.0 (bundled with PyVISA)
      Binary library: Not found
   py:
      Version: 0.6.1
      ASRL INSTR: Available via PySerial (3.5)
      USB INSTR: Available via PyUSB (1.2.1). Backend: libusb1
      USB RAW: Available via PyUSB (1.2.1). Backend: libusb1
      TCPIP INSTR: Available 
         Resource discovery:
         - VXI-11: ok
         - hislip: ok
      VICP INSTR:
         Please install PyVICP to use this resource type.
      TCPIP SOCKET: Available 
      GPIB INSTR:
         Please install linux-gpib (Linux) or gpib-ctypes (Windows, Linux) to use this resource type. Note that installing gpib-ctypes will give you access to a broader range of funcionality.
         No module named 'gpib'

[Matthieu Dartiailh]

Thanks for the detailed report. This is reminiscent of pyusb/pyusb#432

Could you try fiddling with the call to set_configuration (https://github.com/pyvisa/pyvisa-py/blob/main/pyvisa_py/protocols/usbtmc.py#L216) ? Commenting it out/making it conditional on the device not being configured yet ?

Since I do not have the hardware to reproduce locally, I will need you to test possible fixes, sorry for the inconvenience.

[cpagravel]

@MatthieuDartiailh thanks for pointing me in the right direction. I have a PR to address this which works on in my environment: #352