/usr/lib/python2.7/dist-packages/pyvisa-py/protocols/usbtmc.py is in python-pyvisa-py 0.2-1.
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"""
pyvisa-py.protocols.usbtmc
~~~~~~~~~~~~~~~~~~~~~~~~~~
Implements Session to control USBTMC instruments
Loosely based on PyUSBTMC:python module to handle USB-TMC(Test and Measurement class) devices.
by Noboru Yamamot, Accl. Lab, KEK, JAPAN
This file is an offspring of the Lantz Project.
:copyright: 2014 by PyVISA-py Authors, see AUTHORS for more details.
:license: MIT, see LICENSE for more details.
"""
from __future__ import division, unicode_literals, print_function, absolute_import
import enum
from pyvisa.compat import struct
import time
from collections import namedtuple
import usb
from .usbutil import find_devices, find_interfaces, find_endpoint, usb_find_desc
import sys
if sys.version_info < (3, 2):
def array_to_bytes(arr):
return arr.tostring()
else:
def array_to_bytes(arr):
return arr.tobytes()
class MsgID(enum.IntEnum):
"""From USB-TMC table2
"""
dev_dep_msg_out = 1
request_dev_dep_msg_in = 2
dev_dep_msg_in = 2
vendor_specific_out = 126
request_vendor_specific_in = 127
vendor_specific_in = 127
trigger = 128 # for USB488
class Request(enum.IntEnum):
initiate_abort_bulk_out = 1
check_abort_bulk_out_status = 2
initiate_abort_bulk_in = 3
check_abort_bulk_in_status = 4
initiate_clear = 5
check_clear_status = 6
get_capabilities = 7
indicator_pulse = 64
def find_tmc_devices(vendor=None, product=None, serial_number=None, custom_match=None, **kwargs):
"""Find connected USBTMC devices. See usbutil.find_devices for more info.
"""
def is_usbtmc(dev):
if custom_match and not custom_match(dev):
return False
return bool(find_interfaces(dev, bInterfaceClass=0xfe, bInterfaceSubClass=3))
return find_devices(vendor, product, serial_number, is_usbtmc, **kwargs)
class BulkOutMessage(object):
"""The Host uses the Bulk-OUT endpoint to send USBTMC command messages to the device.
"""
@staticmethod
def build_array(btag, eom, chunk):
size = len(chunk)
return struct.pack('BBBx', MsgID.dev_dep_msg_out, btag, ~btag & 0xFF) + \
struct.pack("<LBxxx", size, eom) + \
chunk + \
b'\0' * ((4 - size) % 4)
class BulkInMessage(namedtuple('BulkInMessage', 'msgid btag btaginverse '
'transfer_size transfer_attributes data')):
"""The Host uses the Bulk-IN endpoint to read USBTMC response messages from the device.
The Host must first send a USBTMC command message that expects a response before
attempting to read a USBTMC response message.
"""
@classmethod
def from_bytes(cls, data):
msgid, btag, btaginverse = struct.unpack_from('BBBx', data)
assert msgid == MsgID.dev_dep_msg_in
transfer_size, transfer_attributes = struct.unpack_from('<LBxxx', data, 4)
data = data[12:]
return cls(msgid, btag, btaginverse, transfer_size, transfer_attributes, data)
@staticmethod
def build_array(btag, transfer_size, term_char=None):
"""
:param transfer_size:
:param btag:
:param term_char:
:return:
"""
if term_char is None:
transfer_attributes = 0
term_char = 0
else:
transfer_attributes = 2
return struct.pack('BBBx', MsgID.request_dev_dep_msg_in, btag, ~btag & 0xFF) + \
struct.pack("<LBBxx", transfer_size, transfer_attributes, term_char)
class USBRaw(object):
"""Base class for drivers that communicate with instruments
via usb port using pyUSB
"""
#: Configuration number to be used. If None, the default will be used.
CONFIGURATION = None
#: Interface index it be used
INTERFACE = (0, 0)
#: Receive and Send endpoints to be used. If None the first IN (or OUT) BULK
#: endpoint will be used.
ENDPOINTS = (None, None)
timeout = 2000
find_devices = staticmethod(find_devices)
def __init__(self, vendor=None, product=None, serial_number=None,
device_filters=None, timeout=None, **kwargs):
super(USBRaw, self).__init__()
self.timeout = timeout
device_filters = device_filters or {}
devices = list(self.find_devices(vendor, product, serial_number, None, **device_filters))
if not devices:
raise ValueError('No device found.')
elif len(devices) > 1:
desc = '\n'.join(str(dev) for dev in devices)
raise ValueError('{} devices found:\n{}\n'
'Please narrow the search criteria'.format(len(devices), desc))
self.usb_dev, other = devices[0], devices[1:]
try:
if self.usb_dev.is_kernel_driver_active(0):
self.usb_dev.detach_kernel_driver(0)
except (usb.core.USBError, NotImplementedError) as e:
pass
try:
self.usb_dev.set_configuration()
except usb.core.USBError as e:
raise Exception('failed to set configuration\n %s' % e)
try:
self.usb_dev.set_interface_altsetting()
except usb.core.USBError as e:
pass
self.usb_intf = self._find_interface(self.usb_dev, self.INTERFACE)
self.usb_recv_ep, self.usb_send_ep = self._find_endpoints(self.usb_intf, self.ENDPOINTS)
def _find_interface(self, dev, setting):
return self.usb_dev.get_active_configuration()[self.INTERFACE]
def _find_endpoints(self, interface, setting):
recv, send = setting
if recv is None:
recv = find_endpoint(interface, usb.ENDPOINT_IN, usb.ENDPOINT_TYPE_BULK)
else:
recv = usb_find_desc(interface, bEndpointAddress=recv)
if send is None:
send = find_endpoint(interface, usb.ENDPOINT_OUT, usb.ENDPOINT_TYPE_BULK)
else:
send = usb_find_desc(interface, bEndpointAddress=send)
return recv, send
def write(self, data):
"""Send raw bytes to the instrument.
:param data: bytes to be sent to the instrument
:type data: bytes
"""
try:
return self.usb_send_ep.write(data)
except usb.core.USBError as e:
raise ValueError(str(e))
def read(self, size):
"""Receive raw bytes to the instrument.
:param size: number of bytes to receive
:return: received bytes
:return type: bytes
"""
if size <= 0:
size = 1
data = array_to_bytes(self.usb_recv_ep.read(size, self.timeout))
return data
def close(self):
return usb.util.dispose_resources(self.usb_dev)
class USBTMC(USBRaw):
RECV_CHUNK = 1024 ** 2
find_devices = staticmethod(find_tmc_devices)
def __init__(self, vendor=None, product=None, serial_number=None, **kwargs):
super(USBTMC, self).__init__(vendor, product, serial_number, **kwargs)
self.usb_intr_in = find_endpoint(self.usb_intf, usb.ENDPOINT_IN, usb.ENDPOINT_TYPE_INTERRUPT)
self.usb_dev.reset()
self.usb_dev.set_configuration()
time.sleep(0.01)
self._get_capabilities()
self._btag = 0
if not (self.usb_recv_ep and self.usb_send_ep):
raise ValueError("TMC device must have both Bulk-In and Bulk-out endpoints.")
def _get_capabilities(self):
cap = self.usb_dev.ctrl_transfer(
usb.util.build_request_type(usb.util.CTRL_IN,
usb.util.CTRL_TYPE_CLASS,
usb.util.CTRL_RECIPIENT_INTERFACE),
Request.get_capabilities,
0x0000,
self.usb_intf.index,
0x0018,
timeout=self.timeout)
def _find_interface(self, dev, setting):
interfaces = find_interfaces(dev, bInterfaceClass=0xFE, bInterfaceSubClass=3)
if not interfaces:
raise ValueError('USB TMC interface not found.')
elif len(interfaces) > 1:
pass
return interfaces[0]
def write(self, data):
"""Send raw bytes to the instrument.
:param data: bytes to be sent to the instrument
:type data: bytes
"""
begin, end, size = 0, 0, len(data)
bytes_sent = 0
raw_write = super(USBTMC, self).write
while not end > size:
begin, end = end, begin + self.RECV_CHUNK
self._btag = (self._btag % 255) + 1
data = BulkOutMessage.build_array(self._btag, end > size, data[begin:end])
bytes_sent += raw_write(data)
return bytes_sent
def read(self, size):
recv_chunk = self.RECV_CHUNK
eom = False
raw_read = super(USBTMC, self).read
raw_write = super(USBTMC, self).write
received = b''
while not eom:
self._btag = (self._btag % 255) + 1
req = BulkInMessage.build_array(self._btag, recv_chunk, None)
raw_write(req)
resp = raw_read(recv_chunk)
response = BulkInMessage.from_bytes(resp)
received += response.data
eom = response.transfer_attributes & 1
return received
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