FAQ
Q: Can I connect the RJ45 interface to a switch or router?
A: No. The RJ45 is used only as a connector; it carries RS485 signals, along with a 5 V auxiliary power output and GND pins. It is not an Ethernet interface. Do not connect it to switches, routers, or any Ethernet ports.
Q: Can I use a standard T568B Ethernet cable to connect the device?
A: A standard straight-through cable maintains the T568B pin-to-pin mapping, but you must still verify that the RJ45 pinout on the peer device matches this product. If the pinout differs, use an adapter board or a custom cable; do not rely solely on the connector shape.
Q: How do I confirm the RJ45 pinout?
A: Pin assignments: 1=A, 2=B, 3=NC, 4=5 V, 5=5 V, 6=NC, 7=GND, 8=GND. The maximum output current for the 5 V auxiliary supply is 100 mA. If the peer does not require power, leave pins 4 and 5 disconnected.
Q: I installed the driver but still do not see the serial port. What should I do?
A: Verify that the FTDI VCP driver for your operating system is installed, then unplug and reconnect the converter. On Windows, you can uninstall the malfunctioning device in Device Manager and scan for hardware changes. If it still is not recognized, try a different USB port or host computer.
Q: Can I use this on Linux systems?
A: Yes. The product supports Windows, macOS, Linux, Android, and WinCE. The actual device name and driver loading method depend on the operating system.
Q: Can I use Modbus RTU with this product?
A: The product performs only USB-to-RS485 physical-layer conversion and does not include a built-in Modbus protocol stack. Modbus function codes, register read/write operations, and data parsing must be implemented by the host software or master application.
Q: I cannot communicate after wiring. How do I troubleshoot?
A: First, verify the RJ45 pinout, A/B polarity, and serial port settings on the peer device. Then check the reference ground, cables, termination resistors, and device addresses. Different manufacturers may assign A/B labels differently; always refer to the peer device manual.
Q: When should I enable the 120 Ω termination resistor?
A: Termination resistors are typically installed only at both ends of the RS485 trunk line. For short distances and low baud rates, keep them disabled. For long-distance or high-speed communication where signal reflection occurs, enable them at both ends of the bus.
Q: Do I always need to connect GND for RS485 communication?
A: For short distances with controlled common-mode voltage, connecting A and B only may suffice. For long distances, multi-node setups, or environments with strong interference, connect GND according to the site grounding scheme to provide a reference potential, while avoiding ground loops that do not conform to site specifications.