在Python中與USB設備通信

Question

我想與USB設備進行通信並將數據發送到USB設備。 我能夠找到設備，但在使用內核驅動程序連接設備時，它會給出USB Error: Resource Busy 。 以下是我的代碼：

    dev = usb.core.find(idVendor=0x0403, idProduct=0x6001)
    dev.set_configuration() 

    cfg = dev.get_active_configuration() 

    dev.attach_kernel_driver(interface) 

    interface_number = cfg[(0,0)].bInterfaceNumber 
    alternate_settting = usb.control.get_interface(interface_number) 
    intf = usb.util.find_descriptor( 
    cfg, bInterfaceNumber = interface_number, 
    bAlternateSetting = alternate_setting) 

    ep = usb.util.find_descriptor(intf,custom_match = \
          lambda e: \
    usb.util.endpoint_direction(e.bEndpointAddress) == \
    usb.util.ENDPOINT_OUT) 

    dev.detach_kernel_driver(interface)

    ep.write("\r"+linea1[:19]+"\n\r"+" "*(20-len(linea2))+linea2)  

Answer 1

假設你使用Linux和libusb-1.0作為PyUSB的后端庫。

根據libusb文檔 ：

// Detach a kernel driver from an interface.
// If successful, you will then be able to claim the interface and perform I/O.
int libusb_detach_kernel_driver (libusb_device_handle *dev, 
                                 int interface_number)  

// Re-attach an interface's kernel driver, which was previously 
// detached using libusb_detach_kernel_driver().
int libusb_attach_kernel_driver(libusb_device_handle *dev,
                                int interface_number)

所以基本上，你需要調用detach_kernel_driver 首先從設備的接口拆下已經連接內核驅動程序（如果有的話），這樣你就可以在你的代碼與它通信（它要么你的代碼或一些內核驅動程序交談設備的接口）。 完成后，您可能需要調用attach_kernel_driver以再次重新附加內核驅動程序。

我相信如果你能確保沒有為給定設備加載內核驅動程序（或者在運行代碼之前手動卸載它），就不需要調用任何C函數/ Python方法。

編輯：

我剛剛得到這段代碼（基於你的樣本）工作。 注意：為簡單起見，我將hardcoded 0作為detach_kernel_driver和attach_kernel_driver接口編號 - 我想你應該讓它變得更聰明。

import usb

dev = usb.core.find(idVendor=0x0403, idProduct=0x6001)

reattach = False
if dev.is_kernel_driver_active(0):
    reattach = True
    dev.detach_kernel_driver(0)

dev.set_configuration() 
cfg = dev.get_active_configuration() 

interface_number = cfg[(0,0)].bInterfaceNumber 
alternate_settting = usb.control.get_interface(dev, interface_number) 
intf = usb.util.find_descriptor(cfg, bInterfaceNumber = interface_number, 
                            bAlternateSetting = alternate_settting) 

ep = usb.util.find_descriptor(intf,custom_match = \
      lambda e: \
    usb.util.endpoint_direction(e.bEndpointAddress) == \
    usb.util.ENDPOINT_OUT) 
ep.write("test\n\r")

# This is needed to release interface, otherwise attach_kernel_driver fails 
# due to "Resource busy"
usb.util.dispose_resources(dev)

# It may raise USBError if there's e.g. no kernel driver loaded at all
if reattach:
    dev.attach_kernel_driver(0)