pyusb读取操作始终返回"1" [英] pyusb reading operation always return '1'

问题描述

我正在尝试使用pyusb为我的代码创建USB驱动程序对象，并且读取操作的返回始终返回"1"，我在网上搜索了一段时间，但找不到任何解决方案，请尝试帮助我了解我在做什么错.

I'm trying to create USB driver object using pyusb for my code, and the return from reading operation always return '1', I search the web for a while, and I couldn't find any solution, please try to help me understand what am I'm doing wrong.

环境特性: 在Windows 10上将python 3.7与pycharm一起使用 当然，在安装pyusb模块之后，导入了所有必需的软件包(usb.core，usb.util).

Environmental properties: Using python 3.7 with pycharm on windows 10. Imported all necessary packages (usb.core, usb.util) of course after installing the pyusb module.

我要构建的对象:

class UsbDev:
    def __init__(self, VID, PID):
        self.output_ep = None
        self.input_ep = None
        self.VID = VID
        self.PID = PID
        self.dev = usb.core.find(idVendor = self.VID, idProduct = self.PID)
        if self.dev is None:
            raise AttributeError('USB device is not connected...')

    def check_device(self, dev_name=None):
        if dev_name is None:
            raise ValueError("device name provided is None")
        if self.dev.product != dev_name:
            raise ValueError('Wrong type of product connected to host')

    def config_device(self):
        self.dev.set_configuration()
        cfg = self.dev.get_active_configuration()
        self.output_ep = usb.util.find_descriptor(cfg[(0, 0)], custom_match=lambda e:
            usb.util.endpoint_direction(e.bEndpointAddress) == usb.util.ENDPOINT_OUT)
        self.input_ep = usb.util.find_descriptor(cfg[(0, 0)], custom_match=lambda e:
            usb.util.endpoint_direction(e.bEndpointAddress) == usb.util.ENDPOINT_IN)

    def read_string(self):
        if self.input_ep is not None:
            ret_array = self.dev.read(self.input_ep.bEndpointAddress,
                                      self.input_ep.wMaxPacketSize)
            self.dev.clear_halt(self.input_ep)
            return ''.join([chr(x) for x in ret_array])  # always returns 1

测试用例:

driver = ud(0x0403, 0xed72)  # HAMEG HO720 Serial Port
driver.check_device('HAMEG HO720')
driver.config_device()
driver.send("*IDN?")    
print(driver.read_string())

预期输出:

HAMEG，HMP4040,055310003，HW50020001/SW2.41

HAMEG,HMP4040,055310003,HW50020001/SW2.41

推荐答案

几天后，我自己解决了这个问题. 似乎某些USB设备需要终止符(在我的情况下是换行符'\ n')，因此在发送带有换行符的消息后，该设备便开始回复.

After a few days, I've solved the problem myself. It appears that some USB devices require a termination character (in my case it was newline char '\n') so upon sending a message with newline the device started to reply.

我希望我的案子对你们有帮助.

I hope that my case helps you guys.

这篇关于pyusb读取操作始终返回"1"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！