USB-COMi+2 Hardware Settings and Pinouts

Inside the unit, there is a 3-pin DIP switch used to select the mode of operation. You need to push down the upper case and slide it open by following the direction of the arrow in the illustration below. You can switch to RS-422 mode or RS-485 mode as per the requirements of your application. After setting the operation mode, you can then proceed to insert the driver CD and start driver installation.

 

 

RS-422 & RS-485 Mode Configuration

 

 

Operation Mode S1 S2 S3
RS-422 4 wire with handshaking ON ON ON
RS-485 Full duplex (4 wire) OFF ON ON
Half duplex (2 wire) with echo OFF OFF ON
Half duplex (2 wire) without echo OFF OFF OFF

 

Termination & Bias Resistor Configuration

Inside the unit, there are 3 × 7 (21 pin) header blocks which are jumpered to enable Tx, Rx, CTS 120Ω termination resistors and Tx, Rx 750Ω biasing resistors.

You will need to push down the upper case and slide it open to set the jumper settings as per the requirements of your application.

 

 

Jumper Function
1-2 enable
2-3 disable
Tx termination of 120Ω. This jumper should always be populated for RS-485 mode.
4-5 enable
5-6 disable
Pull-up Tx+ to VCC by 750Ω bias resistor. This jumper should be populated for pull-up Tx+.
7-8 enable
8-9 disable
Pull-down Tx- to GND by 750Ω bias resistor. This jumper should be populated for pull-down Tx- .
10-11 enable
11-12 disable
Rx termination of 120Ω. This jumper should always be populated for RS-422 mode.
13-14 enable
14-15 disable
Pull-up Rx+ to VCC by 750Ω bias resistor. This jumper should be populated for pull-up Rx+.
16-17 enable
17-18 disable
Pull-down Rx- to GND by 750Ω bias resistor. This jumper should be populated for pull-down Rx-.
19-20 enable
20-21 disable
CTS termination of 120Ω. This jumper should always be populated for RS-422 mode.

 

Note: Sometimes, when operating in RS-422 or RS-485, it is necessary to configure termination and biasing of the data transmission lines. Generally this must be done in the cabling, since this depends on the installation of connections. Before applying the option, check your cable specification for proper impedance matching.

Biasing of data lines must only occur at a single point anywhere in the cabling. USB-COMi+2 provides biasing for ease of installation. Please be sure to disable this inside the unit, if your cabling already provides biasing.

Termination must not be installed in the middle of the cable. It is only permitted at both ends. Since a computer controlled serial port is almost always at one end of the cable, termination is disabled by default.

 

RS-422/485 DB9 Male Connector Pinouts

 

 

RS-422 DB9 Male Connector Pinouts

 

PIN SIGNAL
1 Tx- (A)
2 Tx+ (B)
3 Rx+ (B)
4 Rx- (A)
5 GND
6 RTS- (A)
7 RTS+ (B)
8 CTS+ (B)
9 CTS- (A)

 

RS-485 4-Wire (Full duplex) DB9 Male Connector Pinouts

 

PIN SIGNAL
1 Tx- (A)
2 Tx+ (B)
3 Rx+ (B)
4 Rx- (A)
5 GND

 

RS-485 2-Wire (Half duplex) DB9 Male Connector Pinouts

 

PIN SIGNAL
1 Data- (A)
2 Data+ (B)
5 GND

 

RS-422/485 Signal Wiring

RS-422

Point-to-Point 4 Wire Full Duplex

 

 

RS-422 with Handshaking

 

 

RS-485

Point-to-Point 4 Wire Full Duplex

 

 

Multidrop RS-485 2-Wire Half-duplex