I am trying to connect a Prolific pl2303 to my raspberry pi 4 running raspberry pi os 64 bit. When I look at dmesg I get the following output:

[ 31.714397] cam-dummy-reg: disabling
[ 44.046197] usb 1-1.1: USB disconnect, device number 3
[ 47.254348] usb 1-1.1: new full-speed USB device number 4 using xhci_hcd
[ 47.361386] usb 1-1.1: New USB device found, idVendor=067b,
idProduct=23a3, bcdDevice= 6.05
[ 47.361402] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 47.361407] usb 1-1.1: Product: USB-Serial Controller
[ 47.361412] usb 1-1.1: Manufacturer: Prolific Technology Inc.
[ 47.361417] usb 1-1.1: SerialNumber: ALBAb115819
[ 47.364081] pl2303 1-1.1:1.0: pl2303 converter detected
[ 47.364106] pl2303 1-1.1:1.0: unknown device type, please report to linux-usb@vger.kernel.org

I have tried mailing that address and just got an error returned...

and with lsusb:

lsusb -v
Bus 001 Device 004: ID 067b:23a3 Prolific Technology, Inc. USB-Serial Controller
Couldn't open device, some information will be missing
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x067b Prolific Technology, Inc.
  idProduct          0x23a3
  bcdDevice            6.05
  iManufacturer           1 Prolific Technology Inc.
  iProduct                2 USB-Serial Controller
  iSerial                 3 ALBAb115819
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength       0x0027
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0xa0
      (Bus Powered)
      Remote Wakeup
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0
      bInterfaceProtocol      0
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x000a  1x 10 bytes
        bInterval               1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        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     0x83  EP 3 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0

Any help much appreciated. Thanks

  • I had a similar problem. So I went to Prolific Technology to download the most updated the driver. Problem solved.
    – tlfong01
    Jun 18 at 8:08
  • Do you have a link? I read that there was no need to download drivers as they are included in Linux. After a quick Google I've only found windows drivers.
    – Roaders
    Jun 18 at 13:24
  • Ref: raspberrypi.stackexchange.com/questions/96697/… I checked out more than 20 very old USB to TTL adaptors which have been collecting dust for over 10 years. I bought some of them for WinXP and found they no longer working for Win7. I also bought some for Win7, and found them no good for Win10. Just now I tried all these old guys for my Rpi3B+ Raspian 2019Apr to see if I had any luck. Surprisingly I found the following: Bad = 5 (not sure which driver) Good HL340 = 5 Good PL2302 = 7
    – tlfong01
    Jun 18 at 13:47

1 Answer 1


The answer to this seems to be that this usb device no longer works with raspberry pi os bullseye (kernel version 5.15.32-v8+). On buster (kernel version 5.10.103-v7+) it seems to still work fine. (get kernel version by running uname -r).

I found this on this mail thread: https://lore.kernel.org/linux-usb/YZytZ%2FvRioINvb14@hovoldconsulting.com/T/

it seems like the kernel might be being fixed but I do not know what version of the kernel will contain the fix or how to update the kernel...

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