________________________________________________________________________________________________________________________________________________
RS422 & RS485 Operation
RS422 is a four wire interface and supports full duplex (both transmit and receive active at the same time)
communications.
RS485 is a two wire interface and therefore supports
the Trve and Rve signals together and the Transmit
thereby create the two wire interface required to connect to
RS485 requires one device on the network to be the master and
Remember that by connecting the Transmit and Receive differential pairs together (as above) then when you
transmit you will effectively place the transmit data into your receive buffer! So you need to ensure that you
discard this data before you look for data in your receive buffer.
RS422 RS485
Connector – P5 – GPIO
Pin
Signal
Comments
1
3 volts
3 volts DC source for GPIO signal pull ups etc
2
GPIO 1
GPIO signal
3
GPIO 2
GPIO signal
4
GPIO 3
GPIO signal
5
GPIO 4
GPIO signal
6
GPIO 5
GPIO signal
7
GPIO 6
GPIO signal
8
GPIO 7
GPIO signal
9
GPIO 8
GPIO signal
10
GPIO 9
GPIO signal
11
GPIO 10
GPIO signal
12
GPIO 11
GPIO signal
13
GPIO 12
GPIO signal
14
Reserved
15
0 volts
0 volt reference for GPIO signals
Note:
Beta Touch Computer
____________________________________________________________________________________________________________________________________________
RS422 is a four wire interface and supports full duplex (both transmit and receive active at the same time)
RS485 is a two wire interface and therefore supports half duplex operation. Therefore you need to connect
the Trve and Rve signals together and the Transmit –ve and Receive –ve signals together
required to connect to RS485 devices.
one device on the network to be the master and to set the protocol.
Remember that by connecting the Transmit and Receive differential pairs together (as above) then when you
transmit you will effectively place the transmit data into your receive buffer! So you need to ensure that you
you look for data in your receive buffer.
RS422 RS485
Comments
3 volts DC source for GPIO signal pull ups etc
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
GPIO signal – 3 volts level
0 volt reference for GPIO signals
Beta Touch Computer
_____________________________________
Page | 21
RS422 is a four wire interface and supports full duplex (both transmit and receive active at the same time)
you need to connect
ve signals together to
Remember that by connecting the Transmit and Receive differential pairs together (as above) then when you
transmit you will effectively place the transmit data into your receive buffer! So you need to ensure that you
