Cdtrjyty

In our linux box we have USB -> serial device which was always identified as
/dev/ttyACM0. So I've written a application and until yesterday, everything worked fine. But suddenly (yeah, during the remote presentation ...) the device has stopped to work. After a quick research I've found the the connection has changed to /dev/ttyACM1. it was a little untimely, but now I have a problem - how to identify my device in some unambiguously way? Like, for example the storage drive could be initialized using UUID although the /dev/sd** has changed. Is the there some way to do that for serial device?

Now I use a stupid workaround:

for(int i = 0; i < 10; i ++)

{

    m_port = std::string("/dev/ttyACM") + (char)('0' + i);

    m_fd = open(m_port.c_str(), O_RDWR | O_NOCTTY | O_NDELAY);

}

The link to the device we use.

Since we are talking USB devices and assuming you have udev, you could setup some udev rules.

I guess, and this is just a wild guess, somebody or something unplugged/removed the device and plugged it back in/added the device again, which bumps up the number.

Now, first you need vendor and product id's:

$ lsusb

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Bus 001 Device 011: ID 0403:6001 FTDI FT232 USB-Serial (UART) IC

Next, you need the serial number (in case you have several):

# udevadm info -a -n /dev/ttyUSB1 | grep '{serial}' | head -n1

    ATTRS{serial}=="A6008isP"

Now, lets create a udev rule:

UDEV rules are usually scattered into many files in /etc/udev/rules.d. Create a new file called 99-usb-serial.rules and put the following line in there, I have three devices, each with a a different serial number:

SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A6008isP", SYMLINK+="MySerialDevice"

SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A7004IXj", SYMLINK+="MyOtherSerialDevice"

SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="FTDIF46B", SYMLINK+="YetAnotherSerialDevice"



ls -l /dev/MySerialDevice

lrwxrwxrwx 1 root root 7 Nov 25 22:12 /dev/arduino -> ttyUSB1

If you do not want the serial number, any device from vendor with same chip will then get the same symlink, only one can be plugged in at any given time.

SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", SYMLINK+="arduino"

Taken from here