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!