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#
# This file is part of the PyMeasure package.
#
# Copyright (c) 2013-2024 PyMeasure Developers
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
from pymeasure.instruments import Instrument
from pyvisa.errors import VisaIOError
from pyvisa import constants as vconst
import re
import logging
log = logging.getLogger(__name__)
log.addHandler(logging.NullHandler())
class OxfordVISAError(Exception):
pass
class OxfordInstrumentsBase(Instrument):
"""Base instrument for devices from Oxford Instruments.
Checks the replies from instruments for validity.
:param adapter: A string, integer, or :py:class:`~pymeasure.adapters.Adapter` subclass object
:param string name: The name of the instrument. Often the model designation by default.
:param max_attempts: Integer that sets how many attempts at getting a
valid response to a query can be made
:param \\**kwargs: In case ``adapter`` is a string or integer, additional arguments passed on
to :py:class:`~pymeasure.adapters.VISAAdapter` (check there for details).
Discarded otherwise.
"""
timeoutError = VisaIOError(-1073807339)
regex_pattern = r"^([a-zA-Z])[\d.+-]*$"
def __init__(self, adapter, name="OxfordInstruments Base", max_attempts=5, **kwargs):
kwargs.setdefault('read_termination', '\r')
super().__init__(adapter,
name=name,
includeSCPI=False,
asrl={
'baud_rate': 9600,
'data_bits': 8,
'parity': vconst.Parity.none,
'stop_bits': vconst.StopBits.two,
},
**kwargs)
self.max_attempts = max_attempts
def ask(self, command):
"""Write the command to the instrument and return the resulting ASCII response. Also check
the validity of the response before returning it; if the response is not valid, another
attempt is made at getting a valid response, until the maximum amount of attempts is
reached.
:param command: ASCII command string to be sent to the instrument
:returns: String ASCII response of the instrument
:raises: :class:`~.OxfordVISAError` if the maximum number of attempts is surpassed without
getting a valid response
"""
for attempt in range(self.max_attempts):
# Skip the checks in "write", because we explicitly want to get an answer here
super().write(command)
self.wait_for()
response = self.read()
if self.is_valid_response(response, command):
if command.startswith("R"):
# Remove the leading R of the response
return response.strip("R")
return response
log.debug("Received invalid response to '%s': %s", command, response)
# Clear the buffer and try again
try:
self.read()
except VisaIOError as e_visa:
if e_visa.args == self.timeoutError.args:
pass
else:
raise e_visa
# No valid response has been received within the maximum allowed number of attempts
raise OxfordVISAError(f"Retried {self.max_attempts} times without getting a valid "
"response, maybe there is something worse at hand.")
def write(self, command):
"""Write command to instrument and check whether the reply indicates that the given command
was not understood.
The devices from Oxford Instruments reply with '?xxx' to a command 'xxx' if this command is
not known, and replies with 'x' if the command is understood.
If the command starts with an "$" the instrument will not reply at all; hence in that case
there will be done no checking for a reply.
:raises: :class:`~.OxfordVISAError` if the instrument does not recognise the supplied
command or if the response of the instrument is not understood
"""
super().write(command)
if not command[0] == "$":
response = self.read()
log.debug(
"Wrote '%s' to instrument; instrument responded with: '%s'",
command,
response,
)
if not self.is_valid_response(response, command):
if response[0] == "?":
raise OxfordVISAError("The instrument did not understand this command: "
f"{command}")
else:
raise OxfordVISAError(f"The response of the instrument to command '{command}' "
f"is not valid: '{response}'")
def is_valid_response(self, response, command):
"""Check if the response received from the instrument after a command is valid and
understood by the instrument.
:param response: String ASCII response of the device
:param command: command used in the initial query
:returns: True if the response is valid and the response indicates the instrument
recognised the command
"""
# Handle special cases
# Check if the response indicates that the command is not recognized
if response[0] == "?":
log.debug("The instrument did not understand this command: %s", command)
return False
# Handle a special case for when the status is queried
if command[0] == "X" and response[0] == "X":
return True
# Handle a special case for when the version is queried
if command[0] == "V":
return True
# Handle the other, standard cases
try:
match = re.match(self.regex_pattern, response)
except TypeError:
match = False
if match and not match.groups()[0] == command[0]:
match = False
return bool(match)
def __repr__(self):
return "<OxfordInstrumentsAdapter(adapter='%s')>" % self.adapter.connection.resource_name
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