This project is a RS232 to RS485 interface module
This project provides a
simple and easy solution to connect your computer to a RS485 Network in
either Receiver or Transmitter mode.
This circuit has been
designed around popular MAX232 and MAX485 interface IC.
An Onboard 9 pin female “D”
connects this PCB to the Serial Port cable (not supplied with the Kit).
Connector J1 and J2 provide the MAX232 IC input/output (IO) and
Connector CN1 provide MAX485 IO. An optional Power Supply section can
provide regulated 5V DC to the circuit and can be included to power by
bridging Jumper J4. LED D2 provides visual indication of power on this
board and Diode D1 prevents against reverse polarity connection of power
supply at J3. This circuit can also work on 5V supply from the host
interface which can be provide through J1 in which case you need to
remove Jumper Link @ J4. Connector J2 provide extra connection of the
other set of level shifter with in the MAX232 IC.
RS485 cable is to be
connected at Connector CN2 and are impedance matched with Components R3,
R1 and R4.
Terminal marked “A” on CN1
is the Receive / Transmit control Pin for the RS485 flow control.
Pulling this pin to Gnd will enable the Receiver on the RS485 and
Pulling it High (connecting it to Vcc) will enable it to work in the
To connect the MAX232 IC to
1. Connect Pin marked C on connector J1 to Pin marked
DI on connector CN1
2. Connect Pin marked B on connector J1 to
Pin marked RO on connector CN1
Connector J1 connects to
the Host for power supply and serial In/Out signals.
A – Provides
data from the Computer to the Host (RXD)
B – Provides data to be
sent to the Computer from the Host (TXD)
Supply input 5-12 VDC Max