Use a terminal program like PuTTY or the built-in ZKTeco "Device Test" tool within their software. Send a test command (e.g., READER_VERSION). If you receive a response, the driver is working perfectly.
Many ZK-U485 units use the Prolific PL-2303HX or PL-2303TA chip. Go to prolific.com.tw → Support → Downloads. Download the appropriate driver for your OS (Windows 11 users: note that older PL-2303 chips may not be compatible).
Use a free tool like Termite or PuTTY:
The driver is only half the battle. The RS485 settings matter.