1. Hardware:

• Whether the power supply is normal, it is recommended to use our company's power adapter for power supply.
• Check whether the DIP switch on the back of the device is correct, and default is RS485 mode.

• Check whether the serial port extension cable is normal, or please replace a serial cable  to test.

2. Serial parameters:

Serial port parameters(Band rate, parity, data bit, stop bit) should be consistent with the real serial device. Default is 115200, none, 8, 1.

3. Network parameters:

• If N668 works as TCP Client, whether the parameters of the set TCP server are correct.
• If N668 works as TCP server, local port cannot be set to 0.
• You can connect the serial port of N668 to the computer through a serial port to USB cable for data transmission test.

4. Others

Please turn off the firewall and anti-virus software of computer, and disable other redundant network cards during the test.