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Python : PyUSB can't access usb device

I am trying to read an usb bar code reader from my python script, via the https://github.com/pyusb/pyusb library.
import usb.core
import usb.util
VENDOR_ID = 8208
PRODUCT_ID = 30264
dev = usb.core.find(idVendor=VENDOR_ID,
idProduct=PRODUCT_ID)
dev.set_configuration()
cfg = dev.get_active_configuration()
intf = cfg[(0,0)]
ep = usb.util.find_descriptor(
intf,
# match the first OUT endpoint
custom_match = \
lambda e: \
usb.util.endpoint_direction(e.bEndpointAddress) == \
usb.util.ENDPOINT_IN)
data = ep.read(ep.wMaxPacketSize, 8000000)
Unfortunately, this leads to a "USBError: [Errno 13] Access denied (insufficient permissions)" issue.
I tried to run the script as a sudo, but it didn't help. The script work fine on my Ubuntu laptop, but I am now trying to move it to Mac OS. One of the differences is that I do have a "detach_kernel" before hand on Linux, but this function make a fail with "not implemented on this OS" error with Mac Os...

Get RSSI of non connected bluetooth device

I am currently using raspberry pi and want to get RSSI of a non-connected Bluetooth address.
I am using
import bluetooth
result=bluetooth.lookup_name('XX:XX:XX:XX:XX:XX',timeout=5)
if(result !=None):
print("user near")
else:
print("user far")
but I want to be a little more precise and go to the else block in a closer distance and hence I need an RSSI value. Please help. I am new with raspberry and Python.
(I am working in python3)

Getting the RSSI value on a Raspberry Pi is supported by the BlueZ device API.
In the example below I have used pydbus as the library to access BlueZ's D-Bus API. This example scans for 60 seconds and writes the device address and RSSI value to a file. You could modify the code to take an action when a particular address and RSSI value is found.
from datetime import datetime
from pathlib import Path
import pydbus
from gi.repository import GLib
discovery_time = 60
log_file = Path('/home/pi/device.log')
def write_to_log(address, rssi):
"""Write device and rssi values to a log file"""
now = datetime.now()
current_time = now.strftime('%H:%M:%S')
with log_file.open('a') as dev_log:
dev_log.write(f'Device seen[{current_time}]: {address} # {rssi} dBm\n')
bus = pydbus.SystemBus()
mainloop = GLib.MainLoop()
class DeviceMonitor:
"""Class to represent remote bluetooth devices discovered"""
def __init__(self, path_obj):
self.device = bus.get('org.bluez', path_obj)
self.device.onPropertiesChanged = self.prop_changed
rssi = self.device.GetAll('org.bluez.Device1').get('RSSI')
if rssi:
print(f'Device added to monitor {self.device.Address} # {rssi} dBm')
else:
print(f'Device added to monitor {self.device.Address}')
def prop_changed(self, iface, props_changed, props_removed):
"""method to be called when a property value on a device changes"""
rssi = props_changed.get('RSSI', None)
if rssi is not None:
print(f'\tDevice Seen: {self.device.Address} # {rssi} dBm')
write_to_log(self.device.Address, rssi)
def end_discovery():
"""method called at the end of discovery scan"""
mainloop.quit()
adapter.StopDiscovery()
def new_iface(path, iface_props):
"""If a new dbus interfaces is a device, add it to be monitored"""
device_addr = iface_props.get('org.bluez.Device1', {}).get('Address')
if device_addr:
DeviceMonitor(path)
# BlueZ object manager
mngr = bus.get('org.bluez', '/')
mngr.onInterfacesAdded = new_iface
# Connect to the DBus api for the Bluetooth adapter
adapter = bus.get('org.bluez', '/org/bluez/hci0')
adapter.DuplicateData = False
# Iterate around already known devices and add to monitor
print('Adding already known device to monitor...')
mng_objs = mngr.GetManagedObjects()
for path in mng_objs:
device = mng_objs[path].get('org.bluez.Device1', {}).get('Address', [])
if device:
DeviceMonitor(path)
# Run discovery for discovery_time
adapter.StartDiscovery()
GLib.timeout_add_seconds(discovery_time, end_discovery)
print('Finding nearby devices...')
try:
mainloop.run()
except KeyboardInterrupt:
end_discovery()
If you need to install the gi.repository library then follow the "Installing the system provided PyGObject" for Debian instructions at: https://pygobject.readthedocs.io/en/latest/getting_started.html#ubuntu-getting-started

Bluepy library looks beneficial for RaspberryPI. Dont forget you should run like
"sudo python3 name.py" from terminal.
For more info: https://github.com/IanHarvey/bluepy/tree/master/docs
from bluepy.btle import Scanner
while True:
try:
#10.0 sec scanning
ble_list = Scanner().scan(10.0)
for dev in ble_list:
print("rssi: {} ; mac: {}".format(dev.rssi,dev.addr))
except:
raise Exception("Error occured")

Finding Bluetooth low energy with python

Is it possible for this code to be modified to include Bluetooth Low Energy devices as well? https://code.google.com/p/pybluez/source/browse/trunk/examples/advanced/inquiry-with-rssi.py?r=1
I can find devices like my phone and other bluetooth 4.0 devices, but not any BLE. If this cannot be modified, is it possible to run the hcitool lescan and pull the data from hci dump within python? I can use the tools to see the devices I am looking for and it gives an RSSI in hcidump, which is what my end goal is. To get a MAC address and RSSI from the BLE device.
Thanks!

As I said in the comment, that library won't work with BLE.
Here's some example code to do a simple BLE scan:
import sys
import os
import struct
from ctypes import (CDLL, get_errno)
from ctypes.util import find_library
from socket import (
socket,
AF_BLUETOOTH,
SOCK_RAW,
BTPROTO_HCI,
SOL_HCI,
HCI_FILTER,
)
if not os.geteuid() == 0:
sys.exit("script only works as root")
btlib = find_library("bluetooth")
if not btlib:
raise Exception(
"Can't find required bluetooth libraries"
" (need to install bluez)"
)
bluez = CDLL(btlib, use_errno=True)
dev_id = bluez.hci_get_route(None)
sock = socket(AF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI)
sock.bind((dev_id,))
err = bluez.hci_le_set_scan_parameters(sock.fileno(), 0, 0x10, 0x10, 0, 0, 1000);
if err < 0:
raise Exception("Set scan parameters failed")
# occurs when scanning is still enabled from previous call
# allows LE advertising events
hci_filter = struct.pack(
"<IQH",
0x00000010,
0x4000000000000000,
0
)
sock.setsockopt(SOL_HCI, HCI_FILTER, hci_filter)
err = bluez.hci_le_set_scan_enable(
sock.fileno(),
1, # 1 - turn on; 0 - turn off
0, # 0-filtering disabled, 1-filter out duplicates
1000 # timeout
)
if err < 0:
errnum = get_errno()
raise Exception("{} {}".format(
errno.errorcode[errnum],
os.strerror(errnum)
))
while True:
data = sock.recv(1024)
# print bluetooth address from LE Advert. packet
print(':'.join("{0:02x}".format(x) for x in data[12:6:-1]))
I had to piece all of that together by looking at the hcitool and gatttool source code that comes with Bluez. The code is completely dependent on libbluetooth-dev so you'll have to make sure you have that installed first.
A better way would be to use dbus to make calls to bluetoothd, but I haven't had a chance to research that yet. Also, the dbus interface is limited in what you can do with a BLE connection after you make one.
EDIT:
Martin Tramšak pointed out that in Python 2 you need to change the last line to print(':'.join("{0:02x}".format(ord(x)) for x in data[12:6:-1]))

You could also try pygattlib. It can be used to discover devices, and (currently) there is a basic support for reading/writing characteristics. No RSSI for now.
You could discover using the following snippet:
from gattlib import DiscoveryService
service = DiscoveryService("hci0")
devices = service.discover(2)
DiscoveryService accepts the name of the device, and the method discover accepts a timeout (in seconds) for waiting responses. devices is a dictionary, with BL address as keys, and names as values.
pygattlib is packaged for Debian (or Ubuntu), and also available as a pip package.

python script to detect hot-plug event

I'm trying to use python to detect mouse and keyboard event, and tolerant the hot-plug action during the detection. I write this script to automatically detect the keyboard and mouse plug-ins in run-time and output all the keyboard and mouse events. I use evdev and pyudev packages to realize this function. I have my scripts mostly working, including keyboard and mouse event detection and plug-in detection. However, whenever I plug-out the mouse, many weird things happen and my script could not work properly. I have several confusions here.
(1) Whenever the mouse is plugged into the system, there are two files generated in /dev/input/ folder, including ./mouseX and ./eventX. I try to cat to see the output from both source and there are indeed differences, but I do not understand why linux will have ./mouseX even if ./eventX already exists?
(2) Whenever I unplug my mouse, the ./mouseX unplug event comes first, which I did not use in evdev, and this leads to the failure of the script because ./eventX(where I read the data in the script) is unplugged simultaneously but I could only detect ./eventX in the next round. I use a trick(variable i in my script) to bypass this issue, but even though I could successfully delete the mouse device, the select.select() begins endless input reading even though I did not type anything to the keyboard.
The script is listed below(modified based on answers from previous post), thanks beforehand for your attention!
#!/usr/bin/env python
import pyudev
from evdev import InputDevice, list_devices, categorize
from select import select
context = pyudev.Context()
monitor = pyudev.Monitor.from_netlink(context)
monitor.filter_by(subsystem='input')
monitor.start()
devices = map(InputDevice, list_devices())
dev_paths = []
finalizers = []
for dev in devices:
if "keyboard" in dev.name.lower():
dev_paths.append(dev.fn)
elif "mouse" in dev.name.lower():
dev_paths.append(dev.fn)
devices = map(InputDevice, dev_paths)
devices = {dev.fd : dev for dev in devices}
devices[monitor.fileno()] = monitor
count = 1
while True:
r, w, x = select(devices, [], [])
if monitor.fileno() in r:
r.remove(monitor.fileno())
for udev in iter(functools.partial(monitor.poll, 0), None):
# we're only interested in devices that have a device node
# (e.g. /dev/input/eventX)
if not udev.device_node:
break
# find the device we're interested in and add it to fds
for name in (i['NAME'] for i in udev.ancestors if 'NAME' in i):
# I used a virtual input device for this test - you
# should adapt this to your needs
if 'mouse' in name.lower() and 'event' in udev.device_node:
if udev.action == 'add':
print('Device added: %s' % udev)
dev = InputDevice(udev.device_node)
devices[dev.fd] = dev
break
if udev.action == 'remove':
print('Device removed: %s' % udev)
finalizers.append(udev.device_node)
break
for path in finalizers:
for dev in devices.keys():
if dev != monitor.fileno() and devices[dev].fn == path:
print "delete the device from list"
del devices[dev]
for i in r:
if i in devices.keys() and count != 0:
count = -1
for event in devices[i].read():
count = count + 1
print(categorize(event))

The difference between mouseX and eventX is, generally speaking, is eventX is the evdev device, whereas mouseX is the "traditional" device (which, for example, doesn't support various evdev ioctls.)
I don't know what's wrong with the code you posted, but here is a code snippet which does the right thing.
#!/usr/bin/env python
import pyudev
import evdev
import select
import sys
import functools
import errno
context = pyudev.Context()
monitor = pyudev.Monitor.from_netlink(context)
monitor.filter_by(subsystem='input')
# NB: Start monitoring BEFORE we query evdev initially, so that if
# there is a plugin after we evdev.list_devices() we'll pick it up
monitor.start()
# Modify this predicate function for whatever you want to match against
def pred(d):
return "keyboard" in d.name.lower() or "mouse" in d.name.lower()
# Populate the "active devices" map, mapping from /dev/input/eventXX to
# InputDevice
devices = {}
for d in map(evdev.InputDevice, evdev.list_devices()):
if pred(d):
print d
devices[d.fn] = d
# "Special" monitor device
devices['monitor'] = monitor
while True:
rs, _, _ = select.select(devices.values(), [], [])
# Unconditionally ping monitor; if this is spurious this
# will no-op because we pass a zero timeout. Note that
# it takes some time for udev events to get to us.
for udev in iter(functools.partial(monitor.poll, 0), None):
if not udev.device_node: break
if udev.action == 'add':
if udev.device_node not in devices:
print "Device added: %s" % udev
try:
devices[udev.device_node] = evdev.InputDevice(udev.device_node)
except IOError, e:
# udev reports MORE devices than are accessible from
# evdev; a simple way to check is see if the devinfo
# ioctl fails
if e.errno != errno.ENOTTY: raise
pass
elif udev.action == 'remove':
# NB: This code path isn't exercised very frequently,
# because select() will trigger a read immediately when file
# descriptor goes away, whereas the udev event takes some
# time to propagate to us.
if udev.device_node in devices:
print "Device removed (udev): %s" % devices[udev.device_node]
del devices[udev.device_node]
for r in rs:
# You can't read from a monitor
if r.fileno() == monitor.fileno(): continue
if r.fn not in devices: continue
# Select will immediately return an fd for read if it will
# ENODEV. So be sure to handle that.
try:
for event in r.read():
pass
print evdev.categorize(event)
except IOError, e:
if e.errno != errno.ENODEV: raise
print "Device removed: %s" % r
del devices[r.fn]

Problems with pyUSB

I have been trying to make a program with Python which sends commands to a DYMO labelmanager PnP usb device. I tried installing pyUSB and tried the code provided in pyUSB tutorial to figure out a bit how the USB communicating works, but it doesn't work. Code from pyUSB tutorial:
(I have changed the idVendor and idProduct to cope with my device. It finds the device but writing fails)
import usb.core
import usb.util
# find our device
dev = usb.core.find(idVendor=0x0922, idProduct=0x1001)
# was it found?
if dev is None:
raise ValueError('Device not found')
# set the active configuration. With no arguments, the first
# configuration will be the active one
dev.set_configuration()
# get an endpoint instance
cfg = dev.get_active_configuration()
interface_number = cfg[(0,0)].bInterfaceNumber
alternate_setting = usb.control.get_interface(interface_number)
intf = usb.util.find_descriptor(
cfg, bInterfaceNumber = interface_number,
bAlternateSetting = alternate_setting
)
ep = usb.util.find_descriptor(
intf,
# match the first OUT endpoint
custom_match = \
lambda e: \
usb.util.endpoint_direction(e.bEndpointAddress) == \
usb.util.ENDPOINT_OUT
)
assert ep is not None
# write the data
ep.write('test')
and it gives an error:
Traceback (most recent call last):
File "C:\Python27\proc\labelprinttest.py", line 18, in <module>
alternate_setting = usb.control.get_interface(interface_number)
TypeError: get_interface() takes exactly 2 arguments (1 given)
where is the problem?
(well of course there reads that the function takes 2 arguments and only 1 is given, but I have tried to investigate and I have no idea what the other needed argument is)

The definition of get_interface() is as follows:
def get_interface(dev, bInterfaceNumber):
r"""Get the current alternate setting of the interface.
dev is the Device object to which the request will be
sent to.
"""
So, try to call it using usb.control.get_interface(dev, interface_number)