PyVisa-USB超时错误无法清除，必须重启？求调试建议

问题描述 #

应用通过USB-GPIB端口与Anritsu仪器通信，固定周期读取结果。偶尔会在仪器读取数据时误调用Read_data函数，触发Timeout错误导致应用停止。重启应用后，pyvisa能找到并连接仪器，但发送第一条命令*IDN?时出现超时错误，且该问题会持续到系统完全重启。

错误日志 #

('USB0::1003::8293::ANRITSU_0_0000::0::INSTR',)
Found VNA USB0::1003::8293::ANRITSU_0_0000::0::INSTR
Attached
[2022-09-17 23:14:31,349] ERROR in app: Exception on / [GET]
Traceback (most recent call last):
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa_py/protocols/usbtmc.py", line 256, in write
    return self.usb_send_ep.write(data)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/usb/core.py", line 408, in write
    return self.device.write(self, data, timeout)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/usb/core.py", line 989, in write
    return fn(
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/usb/backend/libusb1.py", line 837, in bulk_write
    return self.__write(self.lib.libusb_bulk_transfer,
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/usb/backend/libusb1.py", line 938, in __write
    _check(retval)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/usb/backend/libusb1.py", line 602, in _check
    raise USBTimeoutError(_strerror(ret), ret, _libusb_errno[ret])


    usb.core.USBTimeoutError: [Errno 110] Operation timed out
    
During handling of the above exception, another exception occurred:


Traceback (most recent call last):
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/flask/app.py", line 2070, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/flask/app.py", line 1508, in full_dispatch_request
    self.try_trigger_before_first_request_functions()
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/flask/app.py", line 1560, in try_trigger_before_first_request_functions
    self.ensure_sync(func)()
  File "/home/xilinx/Anritsu_GPIB/VNA/routes.py", line 44, in intialize_VNA
    print(anritsu.VNA.query('*IDN?'))
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa/resources/messagebased.py", line 642, in query
    self.write(message)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa/resources/messagebased.py", line 197, in write
    count = self.write_raw(message.encode(enco))
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa/resources/messagebased.py", line 157, in write_raw
    return self.visalib.write(self.session, message)[0]
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa_py/highlevel.py", line 543, in write
    written, status_code = self.sessions[session].write(data)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa_py/usb.py", line 179, in write
    count = self.interface.write(data)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa_py/protocols/usbtmc.py", line 436, in write
    bytes_sent += raw_write(data)
  File "/usr/local/share/pynq-venv/lib/python3.8/site-packages/pyvisa_py/protocols/usbtmc.py", line 258, in write
    raise ValueError(str(e))
ValueError: [Errno 110] Operation timed out

调试与解决建议 #

• 添加操作互斥锁：在调用Read_data或其他仪器操作函数前，使用threading.Lock实现互斥，确保同一时间只有一个操作请求发送给仪器，避免并发调用导致的设备状态异常。
• 强制重置USB设备：应用重启时，不依赖pyvisa的自动连接，直接用pyusb重置目标USB设备，清除异常状态：

  import usb.core
  import usb.util
  
  # 替换为仪器的USB VID和PID（从设备地址中提取：1003是VID，8293是PID）
  VID = 0x1003
  PID = 0x8293
  
  device = usb.core.find(idVendor=VID, idProduct=PID)
  if device:
      # 分离内核驱动（如果存在）
      if device.is_kernel_driver_active(0):
          device.detach_kernel_driver(0)
      # 释放资源并重置设备
      usb.util.dispose_resources(device)
      device.reset()
  

  执行完重置后再用pyvisa重新连接，无需重启系统即可恢复通信。
• 实现超时重试机制：对仪器命令添加重试逻辑，捕获超时异常后重试2-3次，同时适当延长超时时间：

  def safe_instr_query(instrument, command, timeout=5000, max_retries=3):
      for _ in range(max_retries):
          try:
              instrument.timeout = timeout
              return instrument.query(command)
          except Exception as e:
              if "timeout" in str(e).lower():
                  continue
              raise
      raise TimeoutError(f"Command '{command}' failed after {max_retries} retries")
  

• 发送仪器状态恢复命令：在重置USB设备后，立即发送*CLS（清除状态寄存器）或*RST（重置仪器到默认状态）命令，帮助仪器回到可正常响应的状态。
• 排查适配器兼容性：部分廉价USB-GPIB适配器在超时后容易锁死，尝试更换官方认证的适配器，或更新适配器固件。
• 启用pyvisa调试日志：开启pyvisa的详细日志，查看通信过程中的数据包交互细节，定位问题根源：

  import pyvisa
  pyvisa.log_to_screen()
  

内容的提问来源于stack exchange，提问作者bierkof