Cygnal Integrated Products serial port on Linux

I have an infrared thermometer which operates on a virtual serial port over USB, which I am trying to use on Debian Linux. Unfortunately, the system does not enumerate a /dev/ttyUSB device.

Here is the dmesg for the device:

usb 5-1: new full-speed USB device number 3 using uhci_hcd
usb 5-1: New USB device found, idVendor=10c4, idProduct=834b
usb 5-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 5-1: Product: Infrared Online Sensor Adapter
usb 5-1: Manufacturer: Silicon Labs
usb 5-1: SerialNumber: CT00092755

And here is the lsusb -v:

Bus 005 Device 003: ID 10c4:834b Cygnal Integrated Products, Inc.
Couldn't open device, some information will be missing
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.10
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x10c4 Cygnal Integrated Products, Inc.
  idProduct          0x834b
  bcdDevice            1.00
  iManufacturer           1
  iProduct                2
  iSerial                 3
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           32
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0
      bInterfaceProtocol      0
      iInterface              2
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0

How can I get this working, so I can connect to it with the serial port?

Solution

It turns out this devices uses a standard Silicon Labs CP2102 interface chip, which the device manufacturer loaded with a custom idProduct number. While the chip is 100% compatible with the cp210x.ko driver, the idProduct is not recognized by the system, and does not associate the driver with it.

At this point, there are several possible solutions:

Manually direct the system to use the cp210x.ko driver with this idProduct.
Add the idProduct to the open source driver, compile, and install it. Then try to push the changes into standard Linux repositories.
Replace the customized chip with generic one.
Rewrite the idProduct on the chip.

I chose to rewrite the idProduct. Silicon Labs has a free utility to do just this. I set the idProduct=EA60, which is the default for this chip. The device is now recognized by the standard built-in driver, and works perfectly.