Serial port configuration of raspberry pie

Because of the raspberry pie uart Not enough use , So what we're using is usb To serial port . But there is a problem . When usb The devices are inserted in different order , Its device nodes will be different , Sometimes it's ttyUSB0, Sometimes it's ttyUSB1 Or other . According to this question , After Baidu found a simple solution . That's through udev To statically set the name of the file node . About udev No discussion here . I apply it directly .

First of all ttyUSB0 For example ：

Input udevadm info -a /dev/ttyUSB0

The printed information is as follows ：

looking at device

'/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/ttyUSB0/tty/ttyUSB0':

    KERNEL=="ttyUSB0"

    SUBSYSTEM=="tty"

    DRIVER==""

 

  looking at parent device

'/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4/1-1.4:1.0/ttyUSB0':

    KERNELS=="ttyUSB0"

    SUBSYSTEMS=="usb-serial"

    DRIVERS=="ch341-uart"

    ATTRS{port_number}=="0"

 

  looking at parent device '/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4/1-1.4:1.0':

    KERNELS=="1-1.4:1.0"

    SUBSYSTEMS=="usb"

    DRIVERS=="ch341"

    ATTRS{bInterfaceClass}=="ff"

    ATTRS{bInterfaceSubClass}=="01"

    ATTRS{bInterfaceProtocol}=="02"

    ATTRS{bNumEndpoints}=="03"

    ATTRS{authorized}=="1"

    ATTRS{supports_autosuspend}=="1"

    ATTRS{bAlternateSetting}==" 0"

    ATTRS{bInterfaceNumber}=="00"

 

  looking at parent device '/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4':

    KERNELS=="1-1.4"

    SUBSYSTEMS=="usb"

    DRIVERS=="usb"

    ATTRS{bDeviceSubClass}=="00"

    ATTRS{bDeviceProtocol}=="00"

    ATTRS{devpath}=="1.4"

    ATTRS{idVendor}=="1a86"

    ATTRS{speed}=="12"

    ATTRS{bNumInterfaces}==" 1"

    ATTRS{bConfigurationValue}=="1"

    ATTRS{bMaxPacketSize0}=="8"

    ATTRS{busnum}=="1"

    ATTRS{devnum}=="4"

    ATTRS{configuration}==""

    ATTRS{bMaxPower}=="96mA"

    ATTRS{authorized}=="1"

    ATTRS{bmAttributes}=="80"

    ATTRS{bNumConfigurations}=="1"

    ATTRS{maxchild}=="0"

    ATTRS{bcdDevice}=="0254"

    ATTRS{avoid_reset_quirk}=="0"

    ATTRS{quirks}=="0x0"

    ATTRS{version}==" 1.10"

    ATTRS{urbnum}=="20"

    ATTRS{ltm_capable}=="no"

    ATTRS{removable}=="removable"

    ATTRS{idProduct}=="7523"

    ATTRS{bDeviceClass}=="ff"

ATTRS{product}=="USB2.0-Serial"

......... The printed information is followed by , But there's no need for , So I didn't post it ........

Okay , The blue font above is the information we need .

As for why we choose this   

looking at parent device '/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.4': The message inside , Not the others , My understanding is that , The system is based on the idVendor and idProduct To distinguish between ttyUSB0,ttyUSB1.... etc. USB Serial equipment .

Then get other information in the same way . And then in the catalog /etc/udev/rules.d Next new file 188-usbtty.rules This file can be named differently , But it needs to be .rules file .

Enter the content in the file

KERNEL=="ttyUSB*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", KERNELS=="1-1.2",NAME="ttyUSB0", SYMLINK+="myuart0"

KERNEL=="ttyUSB*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", KERNELS=="1-1.3",NAME="ttyUSB1", SYMLINK+="myuart1"

KERNEL=="ttyUSB*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", KERNELS=="1-1.4",NAME="ttyUSB2", SYMLINK+="myuart2"

KERNEL=="ttyUSB*", SUBSYSTEMS=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", KERNELS=="1-1.5",NAME="ttyUSB3", SYMLINK+="myuart3"

among SYMLINK+="myuart0" Is the name of the static file node you want to set . After restarting the system, you can see the following ：