Ubuntu 22.04: ch34x UART Error

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USB-TTL模块（ch34x）接入PC后，无法识别为正常的USB接口

USB-TTL模块接入PC后，无法识别为正常的USB接口。接着一系列问题排查过程：

  • 确认USB-TTL模块是否被识别

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    pi@localhost:~$ lsusb
    Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 003 Device 003: ID 27c6:5125 Shenzhen Goodix Technology Co.,Ltd. Goodix Fingerprint Device 
    Bus 003 Device 002: ID 0489:e0df Foxconn / Hon Hai 
    Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 002 Device 011: ID 0b95:1790 ASIX Electronics Corp. AX88179 Gigabit Ethernet
    Bus 002 Device 010: ID 05e3:0626 Genesys Logic, Inc. USB3.1 Hub
    Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 001 Device 005: ID 13d3:56f8 IMC Networks ov9734_azurewave_camera
    Bus 001 Device 003: ID 046d:c52f Logitech, Inc. Unifying Receiver
    Bus 001 Device 019: ID 10c4:ea60 Silicon Labs CP210x UART Bridge
    Bus 001 Device 028: ID 1a86:7523 QinHeng Electronics CH340 serial converter
    Bus 001 Device 020: ID 2207:0006 Fuzhou Rockchip Electronics Company rk3xxx
    Bus 001 Device 018: ID 05e3:0610 Genesys Logic, Inc. Hub
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

    QinHeng Electronics CH340 serial converter：表示已经被识别了

  • 确认ch34x驱动是否安装

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    pi@localhost:~$ lsmod | grep usbserial
    usbserial              69632  2 cp210x,ch341

    # 或者使用这种方式查询
    pi@localhost:~$ ls /lib/modules/$(uname -r)/kernel/drivers/usb/serial
    aircable.ko    digi_acceleport.ko  io_ti.ko        kl5kusb105.ko  navman.ko   qcserial.ko      ti_usb_3410_5052.ko   whiteheat.ko
    ark3116.ko     empeg.ko            ipaq.ko         kobil_sct.ko   omninet.ko  quatech2.ko      upd78f0730.ko         wishbone-serial.ko
    belkin_sa.ko   f81232.ko           ipw.ko          mct_u232.ko    opticon.ko  safe_serial.ko   usb_debug.ko          xr_serial.ko
    ch341.ko       f81534.ko           ir-usb.ko       metro-usb.ko   option.ko   sierra.ko        usbserial.ko          xsens_mt.ko
    cp210x.ko      ftdi_sio.ko         iuu_phoenix.ko  mos7720.ko     oti6858.ko  spcp8x5.ko       usb-serial-simple.ko
    cyberjack.ko   garmin_gps.ko       keyspan.ko      mos7840.ko     pl2303.ko   ssu100.ko        usb_wwan.ko
    cypress_m8.ko  io_edgeport.ko      keyspan_pda.ko  mxuport.ko     qcaux.ko    symbolserial.ko  visor.ko

    cp210x,ch341：表示已经加载了cp210x驱动和ch341驱动

  • 查看关于tty的系统日志（重点问题）

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    pi@localhost:~$ sudo dmesg | grep tty
    [290153.696478] usb 1-2.2: ch341-uart converter now attached to ttyUSB0
    [290154.264259] usb 1-2.2: usbfs: interface 0 claimed by ch341 while 'brltty' sets config #1
    [290154.266443] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0


    在浏览器上找到了 brltty 这个进程导致USB-TTL转换失败了。

    brltty 是一个后台进程（守护进程），它使用可刷新的盲文显示器为盲人提供对控制台屏幕（在文本模式下）的访问。它驱动盲文显示器，并提供完整的屏幕查看功能。一些语音功能也被纳入其中。

    解决方法：卸载brltty，执行命令 sudo apt remove brltty

    再次查询 /dev/ttyUSB0 是否存在了：

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    pi@localhost:~$  sudo ls /dev/ttyU*
    /dev/ttyUSB0

    如果不是这种原因引起的，那么就可能是ch34x驱动太旧了，需要更新驱动程序。可以到这个地址去下载驱动：CH341SER_LINUX.ZIP