Use a terminal program like PuTTY or Tera Term:
Loopback test: Short TXD and RXD pins (pins 2 and 3 on DB9). Typing characters should echo back.
In an era of USB-C and wireless connectivity, the humble U232 P9 (often labeled as USB 2.0 to Serial RS232 DB9) remains an essential tool for network engineers, industrial automation technicians, and hobbyists. This adapter bridges the gap between modern laptops without legacy COM ports and older equipment like Cisco routers, CNC machines, GPS receivers, and POS systems. u232 p9 driver windows 10
However, a major frustration arises when plugging this adapter into a Windows 10 PC. The operating system may fail to recognize it, label it as an “Unknown USB Device,” or throw a dreaded Code 10 or Code 31 error. The culprit? Windows 10’s strict driver signature enforcement and the proliferation of counterfeit Prolific chipsets.
This article provides everything you need to successfully install, troubleshoot, and optimize the U232 P9 driver for Windows 10. Use a terminal program like PuTTY or Tera Term :
A: Yes – if you have a genuine Prolific PL-2303 HXD or newer chip, or an FTDI/Silicon Labs adapter. Old H or HX chips will fail.
Zadig can force a generic Windows serial driver (usbser.sys) for stubborn adapters. Loopback test: Short TXD and RXD pins (pins 2 and 3 on DB9)
Note: This method often works but may lack advanced serial features (baud rate above 115200 may be unstable).
| Approach | Method |
|----------|--------|
| Use older driver (v3.3.2.102) | Uninstall current driver, install this version, then disable driver updates via Group Policy or Windows Update settings. |
| Buy a genuine adapter | Look for adapters with FTDI FT232 chip (more reliable, still supported) or genuine PL2303HXD (marked with "HXD"). |
| Use a different USB port (rarely works) | Sometimes USB 2.0 vs 3.0 behaves differently. |
| Enable Test Mode (unsafe) | Run bcdedit /set testsigning on, reboot, then manually install Windows 7 driver. Not recommended for daily use. |