YO Modbus
User guide
v2.1
page 6/33
Figure 3
Connection the YO Modbus device with slave device.
RS485 interface
When connecting RS485 nodes to YO Modbus, connect the A+ line to the RS485 A bus and B− to the
RS485 B bus. GND connects to the ground terminal of the RS485 bus.
This device can be supplied with 6–30 VDC or 5–21 AC.
Optionally, a protective earth cable can be connected. To prevent loop currents, an Earth connection
should be made at only one point on the network.
Line topology may or may not require terminating loads depending on the length of cable used. The
impedance of the termination load should match with line impedance on both ends. The termination
load is usually 120
Ω
on both sides, although the device contains an in-build terminating resistor R
T
.
YO Modbus communicates by sending queries to each device and converting polls, with data from
each slave, into LoRa frames for relay to the application server. Prior to communication between
nodes and the master, it is necessary to configure the serial transmission in the YO Modbus device.
For this, you will need to know the slave addresses and individual registers for reading data.
