I have several USB-serial converters (Prolific) attached to a USB hub. I can't find any udev information that allows me to distinguish these converters depending on the physical port they are connected to.
I hope the device path can give me that information...
/devices/pci0000:00/0000:00:0f.5/usb1/1-3/1-3.1/1-3.1:1.0/ttyUSB0
...but I could not find any documentation that explains the meaning of the numbers (hopefully one of them exactly identifies the physical port). Can somebody explain these numbers and tell me if they allow me to clearly identify the physical port?
I'm no expert in this field, but these are my interpretation of those numbers:
pci0000:00: This is your PCI controller.
0000:00:0f.5: This is the PCI identifier of your USB controller.
usb1: The usb controller itself.
1-3: The identifier of the USB hub. It may be an internal hub, or it may be absent.
1-3.1: Device connected to the first port of that hub.
1-3.1:1.0: Configuration #1, Interface #0 in that device.
So, my guess is that the physical port is identified by 1-3.1, that is the string to the left of the colon in the last piece of the device path.
I don't have a hub around but I'd bet that if you connect it via a hub you'll get something like:
/devices/pci0000:00/0000:00:0f.5/usb1/1-3/1-3.1/1-3.1.1/1-3.1.1:1.0/ttyUSB0
The physical port would be 1-3.1.1, and that last 1 would be the port used in that hub.
This site:
http://hackaday.com/2009/09/18/how-to-write-udev-rules/
references the command:
udevadm info -a -p $(udevadm info -q path -n /dev/ttyUSB0)
(okay, it's a little different, but that command works)
which tells us information like this:
KERNELS=="3-1"
SUBSYSTEMS=="usb"
DRIVERS=="usb"
I've used this information in the past to put together a rule like this one:
KERNELS=="3-1", SUBSYSTEMS=="usb", DRIVERS=="usb", SYMLINK+="USBPORT1"
So every time a device gets plugged into usb port 1, it creates a simlink in the /dev folder that is consistent regardless of what order things are plugged in.
Related
I need to detect when a USB serial device is plugged or unplugged on my embedded system and know what is the tty associated with it.
My system runs over a 2.6 Linux Kernel.
Since I don't have write access to udev rules, nowadays I'm trying to get this information from the file system, looking for modifications in /sys/bus/usb/devices directory. However, I'm facing some problems with this approach.
I know what is the Id BUS of the USB port connected (e.g 1-1.3). So, I search for the associated tty (looking for a directory in /sys/bus/usb/devices/<Id BUS>:1.0/tty/ - e.g. /sys/bus/usb/devices/1-1.3:1.0/tty/ttyACM0). This way I know that I should use /dev/ttyACM0 to communicate with my device.
But, sometimes, this device (/dev/ttyACM0) does not exist.
Is there any better way to get this information?
I even thought trying to get this information from the syslog, but I don't know whether this is a pretty good idea.
Edit:
Only to clarify, my system needs to be able to detect state changes in the USB bus, i.e. detecting when a new device is plugged (and getting the tty name linked to it) or an existing one is unplugged.
The system is monitoring up to N USB/serial devices, which are plugged to it using an USB HUB. During its normal execution new devices can be plugged, existing devices can be removed (or rebooted by a remote command - out of this scope). When a device is rebooted, it could receive a different tty from the previous one used before (e.g. ttyACM0 -> ttyACM3), since the kernel designates to it a tty which is free at the moment, and it is a big problem to me.
Netlink is the preferred mechanism for communication between kernel and userspace.
You would create a Netlink socket with family NETLINK_KOBJECT_UEVENT, listen on that socket and filter out messages that contain SUBSYSTEM=usb and ACTION=add for USB plug events or ACTION=remove for USB unplug events.
I wrote a USB abstraction library called libusbp. You should look at its port_name example, which shows how to use libusbp to get the serial port name (e.g. /dev/ttyACM0) for a USB serial device. Behind the scenes, libusbp gets this information using libudev.
Check if the virtual file is deleted using stat.
#include <sys/statvfs.h>
...
struct stat sb;
return (stat("/dev/ttyUSB0", &sb) == 0); // true if open, false otherwise
My Zaber device is X-MCB2, which is connected to my computer through USB. Command lsusb can show its information as below, but cannot find it in /dev directory.
Bus 003 Device 023: ID 2939:495b
There is another Arduino device connected to my computer as well. Unlike Zaber device, this Arduino device works well, its name in /dev is ttyACM0.
Even if I plugged out the Arduino device, the Zaber device still does NOT show up in /dev directory.
My linux kernel is 2.6.32, and this Zaber device shouldn't need additional driver.
I resolved this issue according to the following link: https://github.com/arduino/Arduino/issues/1389.
echo "0x2939 0x495b" > /sys/bus/usb/drivers/cdc_acm/new_id
Thanks for posting your answer Jeff.
The likely cause of the issue is that Zaber controllers implement USB using CDC ACM, and set 0 for the Protocol field of the USB interface descriptor (indicating that the device doesn't accept AT commands).
In Linux 2.6.32, the CDC ACM kernel driver, which should handle devices
of this type, is written in such a way that it doesn’t take control of
devices whose Protocol field is 0 (instead it has a specific list of
Protocol numbers which it accepts, but that list does not include 0). Instead, you must manually attach it as in the posted solution.
This issue was fixed in kernel 2.6.36.
Here are a list of the commands that will manually attach the Zaber controllers with USB:
X-MCB2:
echo "0x2939 0x495b" > /sys/bus/usb/drivers/cdc_acm/new_id
X-MCB1:
echo "0x2939 0x495a" > /sys/bus/usb/drivers/cdc_acm/new_id
A-MCB2:
echo "0x2939 0x459" > /sys/bus/usb/drivers/cdc_acm/new_id
I have multiple ACR122T smart card devices with no unique serial numbers (from ACS). I need to know which physical smart card I am connected to from within pcsc-lite. I know from using lsusb which USB Port a physical device is on, but how to map that USB port information with SCardGetAttribute(SCARD_ATTR_DEVICE_UNIT) ?
It seems the map should be at the OS level as I cant find a way to read USB Port info (lsusb results) from within the pscs-lite API.
This post mentions a method, Smartcard reader ACR122U has no unique serial number
but I dont understand the details behind "used that dev number to ensure I always used the right reader".
Any help appreciated.
Thanks, -Phil
Disclaimer: I'm working on Windows, not Linux.
The ACR122T (and ACR122U) devices not only have no serial number (other than the one printed on the back) but also have no USB serial number so that they can only be differentiated by the USB port they are plugged in. Additionally all the ACR122Ts and Us I have here (we bought a bunch) identify themselves as "ACS ACR122" to Windows. Using the proprietary API to get the firmware version both the ACR122T and the ACR122U identify themselves as a ACR122U (e.g. "ACR122U207" or "ACR122U214").
That means that the OS itself is not able to differentiate multiple devices in any other way then the USB port it's plugged in.
I also tried to make a connection between the pcsc device and the OS device, but apart from this function (which is only available starting Windows 8) I have not found anything, so it looks to me like there is no way to do that through pcsc calls.
The device unit is given out by the pcsc layer sequentially so you can differentiate between devices you are connected to but not identify a specific device.
Using the lsusb command in Linux I have come to know about bus and device numbers, along with its name of newly attached USB devices.
But how can I know on which device directory (/dev/*) USB device get attached in Linux using command lines only?
It isn't a rule that every device has to show up directly under /dev/, but some device classes will be nested under sub-directories inside /dev/
USB device drivers are a bit different,
If you connect a valid USB device, USB HCI would read the VID:PID and will tell the usb-core that the device with VID:PID combination is connected.
If the usbcore detects any registered driver for the VID:PID combination, it will couple it with the device, and the device file creation would happen accordingly
The device will show in /dev/bus/usb/.., even if, the corresponding driver is not present, to indicate that the device was detected.
You need to have the device driver to have the device in action/operation.
You can verify whether a device driver is coupled to the device through
cat /sys/kernel/debug/usb/devices
Each detected USB device will have an entry here, and also shows the "Driver=" field, to show which driver is associated with your device.
Now, IFF there is a driver, that makes an entry in appropriate /dev tree, you will find the device there.
NOT every device will show up directly under /dev/ in the first level.
say, your mouse/keyboard will not show-up directly under /dev, but inside /dev/input/
Likewise, IF the connected USB device is a char/block device, it MAY show up there, that too have exceptions.
If your device is and ethernet/wifi device, the interface device will NOT show up under /dev/, cross-check with your existing eth0, wlan0, they will not appear directly under /dev/, but will in /proc/net/devices
sda/b/c shows up under /dev directly, because they are block devices and are managed by udev, as such.
Here is an example of lsusb output on my laptop:
Bus 004 Device 123: ID 2001:3c1b D-Link Corp. DWA-127 Wireless N 150 High-Gain Adapter(rev.A1) [Ralink RT3070]
It's the device 123 on the bus 004. /dev/bus/usb/004/123 is just the file for the interested device.
The path might vary on different kernels. The result above holds on kernel 3.15.2
I have two legacy machines connected to a Linux box with USB using the ftdi_sio driver, to /dev/ttyUSB0 and /dev/ttyUSB1. The Linux box is relaying and analyzing the traffic between the machines. When the Linux box boots up, the machines are connected to the files pretty much randomly. The problem is to know which one is which.
I could just ask the devices, of course, but I'd like to avoid the risk of malfunction due to sending wrong data to the wrong device. Is there a way to figure out, for example, the id of the device connected to a tty file?
Check this Using Linux USB page.
/proc/bus/usb/devices lists information about the devices currently attached to the USB bus. This is very useful when trying to figure out if the device is correctly enumerated.
Maybe you can use the output from lsusb -v and look at iProduct + iSerial to determine the order the devices are attached.