uPASS Access | installation guide
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3.2 Communication
3.2.1 RS485
The uPASS Access reader has an RS485 interface for communication with a host system or for configuring reader
settings. The RS485 interface is a 2-wire half-duplex serial communication interface using balanced lines.
STANDARD and OSDP protocol are available.
Connections
RS485 A (-) Balanced RX/TX
RS485 B (+) Balanced RX/TX
Shield connected to DC-ground. Connect to metal case of the external device.
STANDARD firmware
This is the default uPASS Access reader firmware version and implements a simple CR/LF protocol.
The RS485 output message format is described in chapter 5.3.2.
Default baud rate is 9600. This can be changed using the UHFTOOL software.
OSDP firmware
The uPASS Access reader has implemented the OSDP protocol including the Secure Channel Protocol.
Default baud rate is 9600. This may be changed using the OSDP_COMSET command.
Perform a firmware update to change from STANDARD to OSDP (or vice versa).
The firmware update procedure is described in chapter 5.4.
RS485 point-to-point communication
Termination resistors (120 Ω) are recommended to prevent unwanted signal reflections on long RS485 communication
lines. The resistors should be installed at both ends of the communication line.
Figure 4: RS485 point-to-point communication (uPASS Access Rev. C)
The uPASS Access reader models before 2020 (Rev. A/B) have a fixed termination resistor. This means you don’t need
to install a separate termination resistor. See Figure 5.
Figure 5: RS485 point-to-point communication (uPASS Access Rev. A/B)
Notes
• Use shielded twisted pair cable when extending the RS485 wiring beyond the standard 5 meter cable.
• Maximum RS485 cable length 1200 meters (
6000 feet).
• The RS485 interface is disabled while the USB interface is in use.
HOST
Ω
uPASS
Rev. C
uPASS
Rev. A/B
HOST
Ω
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