Rs485 Communication - inout Panelplayer User Manual

9
Serial RS485 communication

9.1 RS485 communication

IMPORTANT:
Panelplayer can be connected to an RS485 communication bus through a serial port,
which is controlled from a master system or by a computer.
Due to interference from outside the serial line, one may find anomalous behaviour from
part of the master system which could cause possible damage to Panelplayer. To avoid
this mishap one must take the following precautions:
1. Do not let the serial cables transit in the same conduits as power cables or cables with
elevated voltage. Maintain a safety distance of at least 10 cm. between these cables.
2. Connect serial cable screen to the ground the on one of the two sides (do not connect
the screen from both sides); in addition, the ground connection of the screen must not
be made in the same point in which piloted circuits of elevated tension are connected.
3. Cut the voltage of the entire system before beginning the wiring of the serial lines:
even dispersed or parasite currents could damage the modules.
Panelplayer withstands serial communication in 4 different modes with the RS485
electrical standard. This type of serial multipoint communication consents the connection
in bus of up to 32 devices, with a maximum distance of 50 metres.
The Panelplayer devices connected to the RS485 bus can not autonomously begin
communication, but they can only respond to a specific request (command) from the
master station (usually a PLC or a computer).
The RS485 connection parameters (speed, parity, check-sum, etc.) are set via the
configuration file config.txt. (par. 9.2).
IMPORTANT:
 The internal electronics of Panelplayer are not galvanically insulated from the RS485
line; in case of short circuit or discharge to ground, it is possible to damage not only
the Panelplayer, but even the master system to which it is connected!
 For the RS485 connection, one must remember to ignore the transmission echo from
the master that is returning through the serial line.
IMPORTANT:

To enable the serial port through the IN5/485A and IN6/485B pins, raise the cover of
the device and move the P1 and P2 jumpers of the diagram as indicated in the
following figure.

With the RS485 connection one must supply termination resistors on both extremes of
the line, to avoid the generation of stationary waves and to define the impedance of
the lines even in absence of transmission. Panelplayer already has within itself a
termination resistor, enabled through a JP1 bridge jumper; to deactivate such
resistance it is sufficient to raise the cover of the device and remove the JP1 jumper
indicated in the figure.
Panelplayer User Manual v.1.4
The RS485 is active in every configuration.
Page 32