Dinplayer And Rs485 - inout Dinplayer D01-MKII User Manual

8
Serial RS485 communication
IMPORTANT:
The RS485 is active in every configuration.
DINplayer 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 DINplayer. 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.
DINplayer 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 DINplayer 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.
IMPORTANT:
The internal electronics of DINplayer 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 DINplayer, 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.

8.1 DINplayer and RS485

To enable the serial port through the 11/485A and 12/485B 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. DINplayer already has within itself a termination resistor,
enabled through a JP1 bridge jumper; to enable such resistance it is sufficient to raise the
cover of the device and move the JP1 jumper as indicated in the figure.
DINplayer User Manual v.2.3
Page 28