# -*- 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 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 1.7
@property
def values_format(self):
return self._values_format
@values_format.setter
def values_format(self, fmt):
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.
"""
return self.query_delay
@ask_delay.setter
def ask_delay(self, value):
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 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
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)
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
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 split the str into individual elements.
If a str is given, data.split(separator) 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
if term:
message += term.encode(enco)
count = self.write_raw(message)
return count
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
def write_values(self, message, values, termination=None, encoding=None):
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)
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.
:rtype: bytes
"""
size = self.chunk_size if size is None else size
loop_status = constants.StatusCode.success_max_count_read
ret = bytes()
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 += chunk
except errors.VisaIOError as e:
logger.debug('%s - exception while reading: %s', self._resource_name, e)
raise
return ret
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)]
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
"""
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)
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()
# Kept for backwards compatibility.
ask = query
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
"""
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)
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)
block = self.read()
return util.from_ascii_block(block, converter, separator, container)
def query_binary_values(self, message, datatype='f', is_big_endian=False, container=list, delay=None, header_fmt='ieee'):
"""Converts an iterable of numbers into a block of data in the ieee format.
: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
:rtype: bytes
"""
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)
block = self.read_raw()
if header_fmt == 'ieee':
offset, data_length = util.parse_ieee_block_header(block)
expected_length = offset + data_length
while len(block) < expected_length:
block += self.read_raw()
try:
if header_fmt == 'ieee':
return util.from_ieee_block(block, datatype, is_big_endian, container)
elif header_fmt == 'empty':
return util.from_binary_block(block, 0, None, datatype, is_big_endian, container)
elif header_fmt == 'hp':
return util.from_binary_block(block, 4, None, datatype, is_big_endian, container)
except ValueError as e:
raise errors.InvalidBinaryFormat(e.args)
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
"""
self.write(message)
if delay is None:
delay = self.query_delay
if delay > 0.0:
time.sleep(delay)
return self.read_values(fmt)
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()
def read_stb(self):
"""Service request status register.
"""
value, retcode = self.visalib.read_stb(self.session)
return value
@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)
