Virtual COM driver in Linux to receive data from USB device

Question

I have a USB barcode reader which is developed for Windows only. But one of the developers told me that as soon as the device detects that it is connected to a virtual COM port it is ready to work. So my question is whether I can create a virtual COM port on Linux and connect the device to this one.

Here the udevadm output when I switch on the device:

udevadm monitor --udev
UDEV  [10487.232696] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2 (usb)
UDEV  [10487.238105] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0 (usb)
UDEV  [10507.430306] add      /class/usbmisc (class)
UDEV  [10507.453800] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1 (usb)
UDEV  [10507.455899] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1/2-1.2.1:1.0 (usb)
UDEV  [10507.456565] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1/2-1.2.1:1.1 (usb)
UDEV  [10507.459065] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1/2-1.2.1:1.1/0003:1AC2:0135.0015 (hid)
UDEV  [10507.461350] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1/2-1.2.1:1.1/usbmisc/hiddev0 (usbmisc)
UDEV  [10507.461669] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2.1/2-1.2.1:1.1/0003:1AC2:0135.0015/hidraw/hidraw2 (hidraw)

The following is the dmsg output:

dmsg
[10473.572851] usb 2-1.2: New USB device found, idVendor=05e3, idProduct=0610
[10473.572863] usb 2-1.2: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[10473.572869] usb 2-1.2: Product: USB2.0 Hub
[10473.573596] hub 2-1.2:1.0: USB hub found
[10473.573971] hub 2-1.2:1.0: 4 ports detected
[10493.661296] usb 2-1.2.1: new high-speed USB device number 41 using ehci-pci
[10493.754539] usb 2-1.2.1: New USB device found, idVendor=1ac2, idProduct=0135
[10493.754550] usb 2-1.2.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[10493.754557] usb 2-1.2.1: Product: *** USB DEVICE  
[10493.754562] usb 2-1.2.1: Manufacturer: ***
[10493.754566] usb 2-1.2.1: SerialNumber: 00000017
[10493.757449] hid-generic 0003:1AC2:0135.0015: hiddev0,hidraw2: USB HID v1.10 Device [*** USB DEVICE  ] on usb-0000:00:1d.0-1.2.1/input1

I played around with socat already, but I was not really successful. I would very much appreciate if one of you would be able to help me.

Thanks, Ralf

David Grayson David Grayson · Accepted Answer · 2014-07-11T03:47:01

I think you don't need to be thinking about virtual COM ports. This bar-code reader looks like it is an HID because I see messages about HID in your dmesg output. You could check for sure by looking at the actual USB descriptors of the device using lsusb.

Since it is an HID, the driver setup should be done automatically when you plug it in, and you should be able to just scan a barcode and it will probably show up on your Linux computer as if it were typed by a keyboard.

By the way, I don't think you can really "create" a virtual COM port. Normally the way it works is that the device's USB descriptors say that it has a USB CDC ACM virtual COM port, and the Linux USB drivers read these descriptors and use it to set up the PC side of the virtual COM port.

Virtual COM driver in Linux to receive data from USB device

1 Answers