User`s manual

PTU-D300 User’s Manual (v2.18.0) NETWORKING
page 29
7.2 PTU Network Connections
Figure 6 illustrates how PTUs can be networked and connected to a host computer via its RS-
232 port. Each PTU has a built-in RS-232 to RS-485 converter, and the host computer can be
connected to the RS-485 controller network by simply connecting to the RS-232 connector on a
PTU. The PTUs are then connected together via an RS-485 multi-drop network (full duplex).
Several issues are important to note when you make your own data cables. First, use a good
quality cable. Though a good quality telephone cord cable can be used, use of a twisted pair cable
is highly recommended. A twisted pair whose impedance is about 100Ω is typically used for
longer RS-485 runs. The twisted pair provides good noise immunity owing to the relative signals
used by the RS-485 standard.
For some applications, the host computer may directly provide RS-485 full-duplex I/O. In
this case, you may directly connect your host computer to the PTU network. For computers with
only RS-232, RS-485 connections may be simply made using an external RS-232 to RS-485
converter. Directed Perception has tested/qualified two converters: ATEN IC-485S and Moxa
A50 which both require a flipped RJ-12 connector (such as a standard phone cord). It is important
to note that the network should be terminated using 120Ω 1% resistors to protect against signal
ringing on the network. Termination is achieved by placing the resistors between the RS-485
Transmit+/Transmit- and Receive+/Receive- wires at each end of the multidrop wiring network.
7.3 PTU Network Software Commands
This section describes the pan-tilt command set used to configure, set and query the network
configuration of your PTU controllers.
7.3.1 Unit Network ID
Description
Specify or query the PTU controller network unit ID number. By default, the
PTU unit ID is set to zero which indicates the PTU controller is not
networked, and the PTU controller is in the default interactive
communications mode. When assigning a unit ID number to a controller, the
unit ID number should be unique, the controller should be the only PTU
controller attached to the host computer or terminal (otherwise other
controllers may be set to the same unit ID number). A unit ID of zero may be
used to put a PTU controller back in interactive (non- networked) mode.
Figure 6: Making PTU Network Connections
HOST
COMPUTER
net/termin. network
PTU-NCONN
120Ω 1% terminator
network net/termin.
PTU-NCONN
120Ω 1% terminator
net/termin. network
PTU-NCONN
• • •
• • •
RS-485 Multi-Drop Network
(full duplex)