Problem

When I connect system serial port COM1 to RS-422/485 devices, why it cannot work and no communication?

Solution

The system BIOS default for serial port is RS-232, if user needs to connect RS-422/485 device that have to into BIOS to change port setting.

Steps,

BIOS => Advanced => COM RS-232/422/485 select => COM1 MODE => [RS-485]