RS232 to RS485 cable pinout

9 pin D-SUB female connector layout
9 pin D-SUB female connector

electrically isolated RS485 communication interface to the PC serial port

EIA-485 cable usually made with twisted pair (like EIA-422) and may
span up to 1200 metres. The recommended arrangement of the wires is as a
connected series of point-to-point nodes, a line or bus. Ideally, the
two ends of the cable will have a termination resistor connected across
the two wires and two powered resistors to bias the lines apart when the
lines are not being driven. The value of each termination resistor
should be equal to the cable impedance (typically, 120 ohms for twisted