Difference between revisions of "Fixed name for USB device"
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== Problem == | == Problem == | ||
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<cite>[[Wikipedia:Udev]]</cite></blockquote> | <cite>[[Wikipedia:Udev]]</cite></blockquote> | ||
| − | + | Find out information about your device | |
| − | + | # sudo udevadm info --query=all --name=/dev/ttyUSB0 | |
| − | + | Look for these lines | |
P: /devices/pci0000:00/0000:00:13.1/usb3/3-2/3-2:1.0/ttyUSB0/tty/ttyUSB0 | P: /devices/pci0000:00/0000:00:13.1/usb3/3-2/3-2:1.0/ttyUSB0/tty/ttyUSB0 | ||
| Line 24: | Line 26: | ||
N: ttyUSB0 | N: ttyUSB0 | ||
... | ... | ||
| − | E: SUBSYSTEM= | + | E: SUBSYSTEM=<span style="color:red">tty</span> |
... | ... | ||
| − | E: ID_SERIAL_SHORT= | + | E: ID_SERIAL_SHORT=<span style="color:blue">FTGCYLSS</span> |
... | ... | ||
| − | + | To enable udev to select the correct adapter, the <tt>ID_SERIAL</tt> or the <tt>ID_SERIAL_SHORT</tt> entry is used. | |
| − | + | Choose a (for you :-) meaningful device name. | |
| − | + | I use <tt>usb-ftdi-1</tt> because its my only serial adapter, all others are for 1-Wire. I also played with the idea of <tt>consumption-watt-meter-s0</tt> ... | |
| − | + | Put this definition | |
| − | + | SUBSYSTEM=="<span style="color:red">tty</span>", ENV{ID_SERIAL_SHORT}=="<span style="color:blue">FTGCYLSS</span>", SYMLINK+="usb-ftdi-1" | |
| − | + | into a rules file | |
| − | + | # sudo echo 'SUBSYSTEM=="'''tty'''", ENV{ID_SERIAL_SHORT}=="'''FTGCYLSS'''", SYMLINK+="usb-ftdi-1"' >>/etc/udev/rules.d/99-usb.rules | |
| + | |||
| + | Restart udev | ||
| + | |||
| + | # sudo udevadm trigger | ||
| + | |||
| + | Check | ||
| + | |||
| + | # sudo ls -al /dev/u* | ||
lrwxrwxrwx 1 root root 7 9. Feb 21:47 /dev/usb-ftdi-1 -> ttyUSB0 | lrwxrwxrwx 1 root root 7 9. Feb 21:47 /dev/usb-ftdi-1 -> ttyUSB0 | ||
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[[File:S0PowerSensorChannel.png]] | [[File:S0PowerSensorChannel.png]] | ||
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Latest revision as of 20:51, 31 August 2014
Problem
If you have no more a real serial port on your system, you will have to use in most cases a USB-serial adapter.
If you have more than adapter, the device (/dev/ttyUSB?) assigned to the adapter during boot time is not in every cases the same.
But it is required to have for the PVLng scripts to have always the same device...
Solution
udev
udev is a device manager for the Linux kernel. Primarily, it manages device nodes in /dev. It is the successor of devfs and hotplug, which means that it handles the /dev directory and all user space actions when adding/removing devices, including firmware load. Wikipedia:Udev
Find out information about your device
# sudo udevadm info --query=all --name=/dev/ttyUSB0
Look for these lines
P: /devices/pci0000:00/0000:00:13.1/usb3/3-2/3-2:1.0/ttyUSB0/tty/ttyUSB0 ... N: ttyUSB0 ... E: SUBSYSTEM=tty ... E: ID_SERIAL_SHORT=FTGCYLSS ...
To enable udev to select the correct adapter, the ID_SERIAL or the ID_SERIAL_SHORT entry is used.
Choose a (for you :-) meaningful device name.
I use usb-ftdi-1 because its my only serial adapter, all others are for 1-Wire. I also played with the idea of consumption-watt-meter-s0 ...
Put this definition
SUBSYSTEM=="tty", ENV{ID_SERIAL_SHORT}=="FTGCYLSS", SYMLINK+="usb-ftdi-1"
into a rules file
# sudo echo 'SUBSYSTEM=="tty", ENV{ID_SERIAL_SHORT}=="FTGCYLSS", SYMLINK+="usb-ftdi-1"' >>/etc/udev/rules.d/99-usb.rules
Restart udev
# sudo udevadm trigger
Check
# sudo ls -al /dev/u* lrwxrwxrwx 1 root root 7 9. Feb 21:47 /dev/usb-ftdi-1 -> ttyUSB0
Here you can see, that the adapter is at he moment also /dev/ttyUSB0
Put this device name into the channel attribute of your Power sensor.
