"""Visa instrument driver based on pyvisa."""
from __future__ import annotations
import logging
import warnings
from importlib.resources import as_file, files
from typing import TYPE_CHECKING, Any
from weakref import finalize
import pyvisa
import pyvisa.constants as vi_const
import pyvisa.resources
from pyvisa.errors import InvalidSession
import qcodes.validators as vals
from qcodes.logger import get_instrument_logger
from qcodes.utils import DelayedKeyboardInterrupt
from .instrument import Instrument
from .instrument_base import InstrumentBase
if TYPE_CHECKING:
from collections.abc import Sequence
VISA_LOGGER = '.'.join((InstrumentBase.__module__, 'com', 'visa'))
log = logging.getLogger(__name__)
def _close_visa_handle(
handle: pyvisa.resources.MessageBasedResource, name: str
) -> None:
try:
if (
handle.session is not None
): # pyvisa sets the session of a handle to None when it is closed
log.info(
"Closing VISA handle to %s as there are no non weak "
"references to the instrument.",
name,
)
handle.close()
except InvalidSession:
# the resource is already closed
pass
[docs]
class VisaInstrument(Instrument):
"""
Base class for all instruments using visa connections.
Args:
name: What this instrument is called locally.
address: The visa resource name to use to connect.
timeout: seconds to allow for responses. Default 5.
terminator: Read and write termination character(s).
If None the terminator will not be set and we
rely on the defaults from PyVisa. Default None.
device_clear: Perform a device clear. Default True.
visalib: Visa backend to use when connecting to this instrument.
This should be in the form of a string '<pathtofile>@<backend>'.
Both parts can be omitted and pyvisa will try to infer the
path to the visa backend file.
By default the IVI backend is used if found, but '@py' will use the
``pyvisa-py`` backend. Note that QCoDeS does not install (or even require)
ANY backends, it is up to the user to do that. see eg:
http://pyvisa.readthedocs.org/en/stable/names.html
metadata: additional static metadata to add to this
instrument's JSON snapshot.
pyvisa_sim_file: Name of a pyvisa-sim yaml file used to simulate the instrument.
The file is expected to be loaded from a python module.
The file can be given either as only the file name in which case it is loaded
from ``qcodes.instruments.sims`` or in the format ``module:filename`` e.g.
``qcodes.instruments.sims:AimTTi_PL601P.yaml`` in which case it is loaded
from the supplied module. Note that it is an error to pass both
``pyvisa_sim_file`` and ``visalib``.
See help for :class:`.Instrument` for additional information on writing
instrument subclasses.
"""
def __init__(
self,
name: str,
address: str,
timeout: float = 5,
terminator: str | None = None,
device_clear: bool = True,
visalib: str | None = None,
pyvisa_sim_file: str | None = None,
**kwargs: Any,
):
super().__init__(name, **kwargs)
self.visa_log = get_instrument_logger(self, VISA_LOGGER)
self.add_parameter(
"timeout",
get_cmd=self._get_visa_timeout,
set_cmd=self._set_visa_timeout,
unit="s",
vals=vals.MultiType(vals.Numbers(min_value=0), vals.Enum(None)),
)
if visalib is not None and pyvisa_sim_file is not None:
raise RuntimeError(
"It's an error to supply both visalib and pyvisa_sim_file as "
"arguments to a VISA instrument"
)
if pyvisa_sim_file is not None:
if ":" in pyvisa_sim_file:
module, pyvisa_sim_file = pyvisa_sim_file.split(":")
else:
module = "qcodes.instrument.sims"
traversable_handle = files(module) / pyvisa_sim_file
with as_file(traversable_handle) as sim_visalib_path:
if not sim_visalib_path.exists():
raise FileNotFoundError(
"Pyvisa-sim yaml file "
"could not be found. Trying to load "
f"file {pyvisa_sim_file} from module: {module}"
)
visalib = f"{sim_visalib_path!s}@sim"
(
visa_handle,
visabackend,
resource_manager,
) = self._connect_and_handle_error(address, visalib)
else:
visa_handle, visabackend, resource_manager = self._connect_and_handle_error(
address, visalib
)
finalize(self, _close_visa_handle, visa_handle, str(self.name))
self.visabackend: str = visabackend
self.visa_handle: pyvisa.resources.MessageBasedResource = visa_handle
"""
The VISA resource used by this instrument.
"""
self.resource_manager = resource_manager
"""
The VISA resource manager used by this instrument.
"""
self.visalib: str | None = visalib
self._address = address
if device_clear:
self.device_clear()
self.set_terminator(terminator)
self.timeout.set(timeout)
def _connect_and_handle_error(
self, address: str, visalib: str | None
) -> tuple[pyvisa.resources.MessageBasedResource, str, pyvisa.ResourceManager]:
try:
visa_handle, visabackend, resource_manager = self._open_resource(
address, visalib
)
except Exception as e:
self.visa_log.exception(f"Could not connect at {address}")
self.close()
raise e
return visa_handle, visabackend, resource_manager
def _open_resource(
self, address: str, visalib: str | None
) -> tuple[pyvisa.resources.MessageBasedResource, str, pyvisa.ResourceManager]:
# in case we're changing the address - close the old handle first
if getattr(self, "visa_handle", None):
self.visa_handle.close()
if visalib is not None:
self.visa_log.info(
f"Opening PyVISA Resource Manager with visalib: {visalib}"
)
resource_manager = pyvisa.ResourceManager(visalib)
visabackend = visalib.split("@")[1]
else:
self.visa_log.info("Opening PyVISA Resource Manager with default backend.")
resource_manager = pyvisa.ResourceManager()
visabackend = "ivi"
self.visa_log.info(f"Opening PyVISA resource at address: {address}")
resource = resource_manager.open_resource(address)
if not isinstance(resource, pyvisa.resources.MessageBasedResource):
resource.close()
raise TypeError("QCoDeS only support MessageBasedResource Visa resources")
return resource, visabackend, resource_manager
[docs]
def set_address(self, address: str) -> None:
"""
Set the address for this instrument.
Args:
address: The visa resource name to use to connect. The address
should be the actual address and just that. If you wish to
change the backend for VISA, use the self.visalib attribute
(and then call this function).
"""
resource, visabackend, resource_manager = self._open_resource(
address, self.visalib
)
self.visa_handle = resource
self._address = address
self.visabackend = visabackend
self.resource_manager = resource_manager
[docs]
def device_clear(self) -> None:
"""Clear the buffers of the device"""
# Serial instruments have a separate flush method to clear
# their buffers which behaves differently to clear. This is
# particularly important for instruments which do not support
# SCPI commands.
# Simulated instruments do not support a handle clear
if self.visabackend == 'sim':
return
flush_operation = (
vi_const.BufferOperation.discard_read_buffer_no_io |
vi_const.BufferOperation.discard_write_buffer
)
if isinstance(self.visa_handle, pyvisa.resources.SerialInstrument):
self.visa_handle.flush(flush_operation)
else:
self.visa_handle.clear()
[docs]
def set_terminator(self, terminator: str | None) -> None:
r"""
Change the read terminator to use.
Args:
terminator: Character(s) to look for at the end of a read and
to end each write command with.
eg. ``\r\n``. If None the terminator will not be set.
"""
if terminator is not None:
self.visa_handle.write_termination = terminator
self.visa_handle.read_termination = terminator
def _set_visa_timeout(self, timeout: float | None) -> None:
# according to https://pyvisa.readthedocs.io/en/latest/introduction/resources.html#timeout
# both float('+inf') and None are accepted as meaning infinite timeout
# however None does not pass the typechecking in 1.11.1
if timeout is None:
self.visa_handle.timeout = float('+inf')
else:
# pyvisa uses milliseconds but we use seconds
self.visa_handle.timeout = timeout * 1000.0
def _get_visa_timeout(self) -> float | None:
timeout_ms = self.visa_handle.timeout
if timeout_ms is None:
return None
else:
# pyvisa uses milliseconds but we use seconds
return timeout_ms / 1000
[docs]
def close(self) -> None:
"""Disconnect and irreversibly tear down the instrument."""
if getattr(self, 'visa_handle', None):
self.visa_handle.close()
if getattr(self, "visabackend", None) == "sim" and getattr(
self, "resource_manager", None
):
# The pyvisa-sim visalib has a session attribute but the resource manager is not generic in the
# visalib type so we cannot get it in a type safe way
known_sessions = getattr(self.resource_manager.visalib, "sessions", ())
try:
this_session = self.resource_manager.session
except InvalidSession:
# this may be triggered when the resource has already been closed
# in that case there is nothing that we can do.
this_session = None
session_found = this_session is not None and this_session in known_sessions
n_sessions = len(known_sessions)
# if this instrument is the last one or there are no connected instruments its safe to reset the device
if (session_found and n_sessions == 1) or n_sessions == 0:
# work around for https://github.com/pyvisa/pyvisa-sim/issues/83
# see other issues for more context
# https://github.com/QCoDeS/Qcodes/issues/5356 and
# https://github.com/pyvisa/pyvisa-sim/issues/82
try:
self.resource_manager.visalib._init()
except AttributeError:
warnings.warn(
"The installed version of pyvisa-sim does not have an `_init` method "
"in its visa library implementation. Cannot reset simulated instrument state. "
"On reconnect the instrument may retain settings set in this session."
)
super().close()
[docs]
def write_raw(self, cmd: str) -> None:
"""
Low-level interface to ``visa_handle.write``.
Args:
cmd: The command to send to the instrument.
"""
with DelayedKeyboardInterrupt():
self.visa_log.debug(f"Writing: {cmd}")
self.visa_handle.write(cmd)
[docs]
def ask_raw(self, cmd: str) -> str:
"""
Low-level interface to ``visa_handle.ask``.
Args:
cmd: The command to send to the instrument.
Returns:
str: The instrument's response.
"""
with DelayedKeyboardInterrupt():
self.visa_log.debug(f"Querying: {cmd}")
response = self.visa_handle.query(cmd)
self.visa_log.debug(f"Response: {response}")
return response
[docs]
def snapshot_base(
self,
update: bool | None = True,
params_to_skip_update: Sequence[str] | None = None,
) -> dict[Any, Any]:
"""
State of the instrument as a JSON-compatible dict (everything that
the custom JSON encoder class :class:`.NumpyJSONEncoder`
supports).
Args:
update: If True, update the state by querying the
instrument. If None only update if the state is known to be
invalid. If False, just use the latest values in memory and
never update.
params_to_skip_update: List of parameter names that will be skipped
in update even if update is True. This is useful if you have
parameters that are slow to update but can be updated in a
different way (as in the qdac). If you want to skip the
update of certain parameters in all snapshots, use the
``snapshot_get`` attribute of those parameters instead.
Returns:
dict: base snapshot
"""
snap = super().snapshot_base(update=update,
params_to_skip_update=params_to_skip_update)
snap["address"] = self._address
snap["terminator"] = self.visa_handle.read_termination
snap["read_terminator"] = self.visa_handle.read_termination
snap["write_terminator"] = self.visa_handle.write_termination
snap["timeout"] = self.timeout.get()
return snap