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Fixes for bitbang mode #431

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Fixes for bitbang mode #431

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64c294a
Do not reattach a driver if freeze requested
Nov 12, 2025
7e21195
Add claim_interface() to match release_interface()
Nov 12, 2025
9c9e7e8
Don't reset the bitmode in bitbanging mode
Nov 12, 2025
95b79eb
Don't set configuration if not necessary
Nov 12, 2025
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28 changes: 18 additions & 10 deletions pyftdi/ftdi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,8 @@
from typing import Callable, Optional, List, Sequence, TextIO, Tuple, Union
from usb.core import (Configuration as UsbConfiguration, Device as UsbDevice,
USBError)
from usb.util import (build_request_type, release_interface, CTRL_IN, CTRL_OUT,
CTRL_TYPE_VENDOR, CTRL_RECIPIENT_DEVICE)
from usb.util import (build_request_type, claim_interface, release_interface,
CTRL_IN, CTRL_OUT, CTRL_TYPE_VENDOR, CTRL_RECIPIENT_DEVICE)
from .misc import to_bool
from .usbtools import UsbDeviceDescriptor, UsbTools

Expand Down Expand Up @@ -522,7 +522,8 @@ def open(self, vendor: int, product: int, bus: Optional[int] = None,
self.open_from_device(device, interface)

def open_from_device(self, device: UsbDevice,
interface: int = 1) -> None:
interface: int = 1,
reset_bitmode: bool = True) -> None:
"""Open a new interface from an existing USB device.

:param device: FTDI USB device (PyUSB instance)
Expand All @@ -531,12 +532,10 @@ def open_from_device(self, device: UsbDevice,
if not isinstance(device, UsbDevice):
raise FtdiError(f"Device '{device}' is not a PyUSB device")
self._usb_dev = device
try:
self._usb_dev.set_configuration()
except USBError:
pass
cfg0 = device[0].bConfigurationValue
# detect invalid interface as early as possible
config = self._usb_dev.get_active_configuration()
cfg = config.bConfigurationValue
if interface > config.bNumInterfaces:
raise FtdiError(f'No such FTDI port: {interface}')
self._set_interface(config, interface)
Expand All @@ -546,10 +545,18 @@ def open_from_device(self, device: UsbDevice,
self._readbuffer = bytearray()
# Drain input buffer
self.purge_buffers()
# Claim the interface
if device.bNumConfigurations > 0 and cfg0 != cfg:
try:
device.set_configuration()
except USBError:
pass
claim_interface(device, self._index - 1)
# Shallow reset
self._reset_device()
# Reset feature mode
self.set_bitmode(0, Ftdi.BitMode.RESET)
if reset_bitmode:
self.set_bitmode(0, Ftdi.BitMode.RESET)
# Init latency
self._latency_threshold = None
self.set_latency_timer(self.LATENCY_MIN)
Expand Down Expand Up @@ -579,7 +586,8 @@ def close(self, freeze: bool = False) -> None:
except FtdiError as exc:
self.log.warning('FTDI device may be gone: %s', exc)
try:
self._usb_dev.attach_kernel_driver(self._index - 1)
if not freeze:
self._usb_dev.attach_kernel_driver(self._index - 1)
except (NotImplementedError, USBError):
pass
self._usb_dev = None
Expand Down Expand Up @@ -838,7 +846,7 @@ def open_bitbang_from_device(self, device: UsbDevice,
:param sync: whether to use synchronous or asynchronous bitbang
:return: actual bitbang baudrate in bps
"""
self.open_from_device(device, interface)
self.open_from_device(device, interface, reset_bitmode=False)
# Set latency timer
self.set_latency_timer(latency)
# Set chunk size
Expand Down
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