StarTech ICUSB234858I - 4 of 8 ports randomly USB-disconnect/reconnect (same chip group every time)

General
1

Hi all,

I’m dealing with a strange intermittent issue on a StarTech ICUSB234858I (8-port USB-to-serial, externally powered) on Windows 11, used in an industrial setup with 5 serial devices connected (RS232/RS485/RS422 mix).

Symptom:
Every few days, while the host software is actively polling the serial ports, 4 of the 8 ports do a full USB disconnect/reconnect (you hear the Windows USB device removed + connected sound within about 1 second). In Device Manager, the adapter shows up as two groups of “USB Serial Converter A/B/C/D” (it has two internal FT4232H chips, one per group of 4 ports). It’s always the SAME group of 4 ports (COM11-14 in my mapping) that drops - the other group (COM15-18) never disconnects.

The “Address” value (in the device’s General properties) for the affected group shifts by +1, overlapping with the address of the unaffected group.

What I’ve already tried:

  • Fully uninstalled/reinstalled FTDI VCP drivers for all 8 ports - no change.
  • External power supply is connected and working.
  • Disabled USB selective suspend on all related devices.
  • Checked Event Viewer thoroughly - this is a genuine USB-level disconnect, not a software timeout or driver hang.

Since it’s always the same chip/port group and driver reinstall didn’t help, my best guess is a hardware fault isolated to one of the two internal FT4232H chips (or its hub branch) in this specific unit.

Has anyone seen this exact failure pattern on the ICUSB234858I (or similar StarTech 8-port FTDI adapters)? Is this a known failure mode? Any other diagnostics worth trying?

Thanks!

2

Hello @stevepinto,

Thank you for posting on the Startech.com Community. I am sorry to hear about the trouble you are having with ICUSB234858I.

Thank you for the detailed post and description of the troubleshooting steps you have already taken. To help determine our next steps can I please ask:

  • What is the make and model of the computer?
  • What are the models of the serial devices connected to the affected ports?
  • Is this the first time you are trying to use ICUSB234858I or has it been in use for some time and this issue just started recently?

If possible, I would also like to suggest testing the unit with a different host computer to confirm if the behavior is isolated to this one system or if it follows the unit to another setup.

I look forward to hearing back from you.

Lukas T