# -*- coding: utf-8 -*-
"""
pyvisa.resources.messagebased
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
High level wrapper for MessageBased Instruments.
This file is part of PyVISA.
:copyright: 2014 by PyVISA Authors, see AUTHORS for more details.
:license: MIT, see LICENSE for more details.
"""
from __future__ import (division, unicode_literals, print_function,
absolute_import)
import contextlib
import time
import warnings
from .. import logger
from .. import constants
from .. import errors
from .. import util
from .resource import Resource
class ValuesFormat(object):
"""Options for reading values.
"""
__slots__ = ('is_binary', 'container',
'datatype', 'is_big_endian',
'converter', 'separator', 'header_fmt')
def __init__(self):
self.is_binary = True
self.datatype = 'f'
self.is_big_endian = False
self.container = list
self.converter = 'f'
self.separator = ','
self.header_fmt = 'ieee'
def use_ascii(self, converter, separator, container=list):
self.converter = converter
self.separator = separator
self.container = container
self.is_binary = False
def use_binary(self, datatype, is_big_endian, container=list,
header_fmt='ieee'):
self.datatype = datatype
self.is_big_endian = is_big_endian
self.container = container
self.is_binary = True
self.header_fmt = header_fmt
class ControlRenMixin(object):
"""Common control_ren method of some messaged based resources.
"""
# It should work for GPIB, USB and some TCPIP
# For TCPIP I found some (all?) NI's VISA library do not handle
# control_ren, but it works for Agilent's VISA library (at least some of
# them)
def control_ren(self, mode):
"""Controls the state of the GPIB Remote Enable (REN) interface line,
and optionally the remote/local state of the device.
Corresponds to viGpibControlREN function of the VISA library.
:param mode: Specifies the state of the REN line and optionally the
device remote/local state. (Constants.GPIB_REN*)
:return: return value of the library call.
:rtype: VISAStatus
"""
return self.visalib.gpib_control_ren(self.session, mode)
[docs]class MessageBasedResource(Resource):
"""Base class for resources that use message based communication.
"""
CR = '\r'
LF = '\n'
_read_termination = None
_write_termination = CR + LF
_encoding = 'ascii'
chunk_size = 20 * 1024
query_delay = 0.0
_values_format = None
def __init__(self, *args, **kwargs):
self._values_format = ValuesFormat()
super(MessageBasedResource, self).__init__(*args, **kwargs)
# This is done for backwards compatibility but will be removed in 1.10
@property
def values_format(self):
warnings.warn('values_format is deprecated and will be removed in '
'1.10', FutureWarning)
return self._values_format
@values_format.setter
def values_format(self, fmt):
warnings.warn('values_format is deprecated and will be removed in '
'1.10', FutureWarning)
self._values_format.is_binary = not (fmt & 0x01 == 0)
if fmt & 0x03 == 1: # single
self._values_format.datatype = 'f'
elif fmt & 0x03 == 3: # double:
self._values_format.datatype = 'd'
else:
raise ValueError("unknown data values fmt requested")
self._values_format.is_big_endian = fmt & 0x04
####
@property
def ask_delay(self):
"""An alias for query_delay kept for backwards compatibility.
"""
warnings.warn('ask_delay is deprecated and will be removed in '
'1.10, use query_delay instead', FutureWarning)
return self.query_delay
@ask_delay.setter
def ask_delay(self, value):
warnings.warn('ask_delay is deprecated and will be removed in '
'1.10, use query_delay instead', FutureWarning)
self.query_delay = value
@property
def encoding(self):
"""Encoding used for read and write operations.
"""
return self._encoding
@encoding.setter
def encoding(self, encoding):
# Test that the encoding specified makes sense.
'test encoding'.encode(encoding).decode(encoding)
self._encoding = encoding
@property
def read_termination(self):
"""Read termination character.
"""
return self._read_termination
@read_termination.setter
def read_termination(self, value):
if value:
# termination character, the rest is just used for verification
# after each read operation.
last_char = value[-1:]
# Consequently, it's illogical to have the real termination
# character twice in the sequence (otherwise reading would stop
# prematurely).
if last_char in value[:-1]:
raise ValueError("ambiguous ending in termination characters")
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR, ord(last_char))
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR_EN,
constants.VI_TRUE)
else:
# The termchar is also used in VI_ATTR_ASRL_END_IN (for serial
# termination) so return it to its default.
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR, ord(self.LF))
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR_EN,
constants.VI_FALSE)
self._read_termination = value
@property
def write_termination(self):
"""Writer termination character.
"""
return self._write_termination
@write_termination.setter
def write_termination(self, value):
self._write_termination = value
[docs] def write_raw(self, message):
"""Write a byte message to the device.
:param message: the message to be sent.
:type message: bytes
:return: number of bytes written.
:rtype: int
"""
return self.visalib.write(self.session, message)
[docs] def write(self, message, termination=None, encoding=None):
"""Write a string message to the device.
The write_termination is always appended to it.
:param message: the message to be sent.
:type message: unicode (Py2) or str (Py3)
:return: number of bytes written.
:rtype: int
"""
term = self._write_termination if termination is None else termination
enco = self._encoding if encoding is None else encoding
if term:
if message.endswith(term):
warnings.warn("write message already ends with "
"termination characters", stacklevel=2)
message += term
count = self.write_raw(message.encode(enco))
return count
[docs] def write_ascii_values(self, message, values, converter='f', separator=',',
termination=None, encoding=None):
"""Write a string message to the device followed by values in ascii
format.
The write_termination is always appended to it.
:param message: the message to be sent.
:type message: unicode (Py2) or str (Py3)
:param values: data to be writen to the device.
:param converter: function used to convert each value.
String formatting codes are also accepted.
Defaults to str.
:type converter: callable | str
:param separator: a callable that join the values in a single str.
If a str is given, separator.join(values) is used.
:type: separator: (collections.Iterable[T]) -> str | str
:return: number of bytes written.
:rtype: int
"""
term = self._write_termination if termination is None else termination
enco = self._encoding if encoding is None else encoding
if term and message.endswith(term):
warnings.warn("write message already ends with "
"termination characters", stacklevel=2)
block = util.to_ascii_block(values, converter, separator)
message = message.encode(enco) + block.encode(enco)
if term:
message += term.encode(enco)
count = self.write_raw(message)
return count
[docs] def write_binary_values(self, message, values, datatype='f',
is_big_endian=False, termination=None,
encoding=None):
"""Write a string message to the device followed by values in binary
format.
The write_termination is always appended to it.
:param message: the message to be sent.
:type message: unicode (Py2) or str (Py3)
:param values: data to be writen to the device.
:param datatype: the format string for a single element. See struct
module.
:param is_big_endian: boolean indicating endianess.
:return: number of bytes written.
:rtype: int
"""
term = self._write_termination if termination is None else termination
enco = self._encoding if encoding is None else encoding
if term and message.endswith(term):
warnings.warn("write message already ends with "
"termination characters", stacklevel=2)
block = util.to_ieee_block(values, datatype, is_big_endian)
message = message.encode(enco) + block
if term:
message += term.encode(enco)
count = self.write_raw(message)
return count
[docs] def write_values(self, message, values, termination=None, encoding=None):
warnings.warn('write_values is deprecated and will be removed in '
'1.10, use write_ascii_values or write_binary_values '
'instead.', FutureWarning)
vf = self.values_format
if vf.is_binary:
return self.write_binary_values(message, values, vf.datatype,
vf.is_big_endian, termination,
encoding)
return self.write_ascii_values(message, values, vf.converter,
vf.separator, termination, encoding)
[docs] def read_bytes(self, count, chunk_size=None, break_on_termchar=False):
"""Read a certain number of bytes from the instrument.
:param count: The number of bytes to read from the instrument.
:type count: int
:param chunk_size: The chunk size to use to perform the reading.
:type chunk_size: int
:param break_on_termchar: Should the reading stop when a termination
character is encountered.
:type brak_on_termchar: bool
:rtype: bytes
"""
chunk_size = chunk_size or self.chunk_size
ret = bytearray()
left_to_read = count
termchar_read = constants.StatusCode.success_termination_character_read
with self.ignore_warning(constants.VI_SUCCESS_DEV_NPRESENT,
constants.VI_SUCCESS_MAX_CNT):
try:
status = None
while len(ret) < count:
size = min(chunk_size, left_to_read)
logger.debug('%s - reading %d bytes (last status %r)',
self._resource_name, size, status)
chunk, status = self.visalib.read(self.session, size)
ret.extend(chunk)
left_to_read -= len(chunk)
if break_on_termchar and status == termchar_read:
break
except errors.VisaIOError as e:
logger.debug('%s - exception while reading: %s\n'
'Buffer content: %r', self._resource_name, e,
ret)
raise
return bytes(ret)
[docs] def read_raw(self, size=None):
"""Read the unmodified string sent from the instrument to the computer.
In contrast to read(), no termination characters are stripped.
:param size: The chunk size to use when reading the data.
:rtype: bytes
"""
return bytes(self._read_raw(size))
def _read_raw(self, size=None):
"""Read the unmodified string sent from the instrument to the computer.
In contrast to read(), no termination characters are stripped.
:param size: The chunk size to use when reading the data.
:rtype: bytearray
"""
size = self.chunk_size if size is None else size
loop_status = constants.StatusCode.success_max_count_read
ret = bytearray()
with self.ignore_warning(constants.VI_SUCCESS_DEV_NPRESENT,
constants.VI_SUCCESS_MAX_CNT):
try:
status = loop_status
while status == loop_status:
logger.debug('%s - reading %d bytes (last status %r)',
self._resource_name, size, status)
chunk, status = self.visalib.read(self.session, size)
ret.extend(chunk)
except errors.VisaIOError as e:
logger.debug('%s - exception while reading: %s\nBuffer '
'content: %r', self._resource_name, e, ret)
raise
return ret
[docs] def read(self, termination=None, encoding=None):
"""Read a string from the device.
Reading stops when the device stops sending (e.g. by setting
appropriate bus lines), or the termination characters sequence was
detected. Attention: Only the last character of the termination
characters is really used to stop reading, however, the whole sequence
is compared to the ending of the read string message. If they don't
match, a warning is issued.
All line-ending characters are stripped from the end of the string.
:rtype: str
"""
enco = self._encoding if encoding is None else encoding
if termination is None:
termination = self._read_termination
message = self._read_raw().decode(enco)
else:
with self.read_termination_context(termination):
message = self._read_raw().decode(enco)
if not termination:
return message
if not message.endswith(termination):
warnings.warn("read string doesn't end with "
"termination characters", stacklevel=2)
return message[:-len(termination)]
[docs] def read_ascii_values(self, converter='f', separator=',', container=list,
delay=None):
"""Read values from the device in ascii format returning an iterable of
values.
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:param converter: function used to convert each element.
Defaults to float
:type converter: callable
:param separator: a callable that split the str into individual
elements. If a str is given, data.split(separator) is
used.
:type: separator: (str) -> collections.Iterable[int] | str
:param container: container type to use for the output data.
:returns: the answer from the device.
:rtype: list
"""
# Use read rather than _read_raw because we cannot handle a bytearray
block = self.read()
return util.from_ascii_block(block, converter, separator, container)
[docs] def read_binary_values(self, datatype='f', is_big_endian=False,
container=list, header_fmt='ieee'):
"""Read values from the device in binary format returning an iterable
of values.
:param datatype: the format string for a single element. See struct
module.
:param is_big_endian: boolean indicating endianess.
Defaults to False.
:param container: container type to use for the output data.
:param header_fmt: format of the header prefixing the data. Possible
values are: 'ieee', 'hp', 'empty'
:returns: the answer from the device.
:rtype: type(container)
"""
block = self._read_raw()
expected_length = 0
if header_fmt == 'ieee':
offset, data_length = util.parse_ieee_block_header(block)
expected_length = offset + data_length
elif header_fmt == 'hp':
offset, data_length = util.parse_hp_block_header(block,
is_big_endian)
expected_length = offset + data_length
if self._read_termination is not None:
expected_length += len(self._read_termination)
while len(block) < expected_length:
block.extend(self._read_raw())
try:
if header_fmt == 'ieee':
return util.from_ieee_block(block, datatype, is_big_endian,
container)
elif header_fmt == 'hp':
return util.from_hp_block(block, datatype, is_big_endian,
container)
elif header_fmt == 'empty':
return util.from_binary_block(block, 0, None, datatype,
is_big_endian, container)
else:
raise
except ValueError as e:
raise errors.InvalidBinaryFormat(e.args)
[docs] def read_values(self, fmt=None, container=list):
"""Read a list of floating point values from the device.
:param fmt: the format of the values. If given, it overrides
the class attribute "values_format". Possible values are bitwise
disjunctions of the above constants ascii, single, double, and
big_endian. Default is ascii.
:param container: the output datatype
:return: the list of read values
:rtype: list
"""
warnings.warn('read_values is deprecated and will be removed in '
'1.10, use read_ascii_values or read_binary_values '
'instead.', FutureWarning)
if not fmt:
vf = self.values_format
if not vf.is_binary:
return util.from_ascii_block(self.read(), container)
data = self._read_raw()
try:
return util.parse_binary(data, vf.is_big_endian,
vf.datatype == 'f')
except ValueError as e:
try:
msg = e.args[0]
except IndexError:
msg = ''
raise errors.InvalidBinaryFormat(msg)
if fmt & 0x01 == 0: # ascii
return util.from_ascii_block(self.read())
data = self._read_raw()
try:
if fmt & 0x03 == 1: # single
is_single = True
elif fmt & 0x03 == 3: # double:
is_single = False
else:
raise ValueError("unknown data values fmt requested")
is_big_endian = fmt & 0x04 # big endian
return util.parse_binary(data, is_big_endian, is_single)
except ValueError as e:
raise errors.InvalidBinaryFormat(e.args)
[docs] def query(self, message, delay=None):
"""A combination of write(message) and read()
:param message: the message to send.
:type message: str
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:returns: the answer from the device.
:rtype: str
"""
self.write(message)
delay = self.query_delay if delay is None else delay
if delay > 0.0:
time.sleep(delay)
return self.read()
def ask(self, message, delay=None):
warnings.warn('ask is deprecated and will be removed in '
'1.10, use query instead.', FutureWarning)
return self.query(message, delay)
[docs] def query_values(self, message, delay=None):
"""Query the device for values returning an iterable of values.
The datatype expected is obtained from `values_format`
:param message: the message to send.
:type message: str
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:returns: the answer from the device.
:rtype: list
"""
warnings.warn('query_values is deprecated and will be removed in '
'1.10, use query_ascii_values or quey_binary_values '
'instead.', FutureWarning)
vf = self.values_format
if vf.is_binary:
return self.query_binary_values(message, vf.datatype,
vf.is_big_endian, vf.container,
delay, vf.header_fmt)
return self.query_ascii_values(message, vf.converter, vf.separator,
vf.container, delay)
[docs] def query_ascii_values(self, message, converter='f', separator=',',
container=list, delay=None):
"""Query the device for values in ascii format returning an iterable of
values.
:param message: the message to send.
:type message: str
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:param converter: function used to convert each element.
Defaults to float
:type converter: callable
:param separator: a callable that split the str into individual
elements. If a str is given, data.split(separator) is
used.
:type: separator: (str) -> collections.Iterable[int] | str
:param container: container type to use for the output data.
:returns: the answer from the device.
:rtype: list
"""
self.write(message)
if delay is None:
delay = self.query_delay
if delay > 0.0:
time.sleep(delay)
return self.read_ascii_values(converter, separator, container,
delay)
[docs] def query_binary_values(self, message, datatype='f', is_big_endian=False,
container=list, delay=None, header_fmt='ieee'):
"""Query the device for values in binary format returning an iterable
of values.
:param message: the message to send to the instrument.
:param datatype: the format string for a single element. See struct
module.
:param is_big_endian: boolean indicating endianess.
Defaults to False.
:param container: container type to use for the output data.
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:returns: the answer from the device.
:rtype: list
"""
if header_fmt not in ('ieee', 'empty', 'hp'):
raise ValueError("Invalid header format. Valid options are 'ieee',"
" 'empty', 'hp'")
self.write(message)
if delay is None:
delay = self.query_delay
if delay > 0.0:
time.sleep(delay)
return self.read_binary_values(datatype, is_big_endian, container,
header_fmt)
def ask_for_values(self, message, fmt=None, delay=None):
"""A combination of write(message) and read_values()
:param message: the message to send.
:type message: str
:param delay: delay in seconds between write and read operations.
if None, defaults to self.query_delay
:returns: the answer from the device.
:rtype: list
"""
warnings.warn('ask_values is deprecated and will be removed in '
'1.10, use query_ascii_values or quey_binary_values '
'instead.', FutureWarning)
self.write(message)
if delay is None:
delay = self.query_delay
if delay > 0.0:
time.sleep(delay)
return self.read_values(fmt)
[docs] def assert_trigger(self):
"""Sends a software trigger to the device.
"""
self.visalib.assert_trigger(self.session,
constants.VI_TRIG_PROT_DEFAULT)
@property
def stb(self):
"""Service request status register."""
return self.read_stb()
[docs] def read_stb(self):
"""Service request status register.
"""
value, retcode = self.visalib.read_stb(self.session)
return value
[docs] @contextlib.contextmanager
def read_termination_context(self, new_termination):
term = self.get_visa_attribute(constants.VI_ATTR_TERMCHAR)
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR,
ord(new_termination[-1]))
yield
self.set_visa_attribute(constants.VI_ATTR_TERMCHAR, term)
# Rohde and Schwarz Device via Passport. Not sure which Resource should be.
MessageBasedResource.register(constants.InterfaceType.rsnrp,
'INSTR')(MessageBasedResource)
