Chengdu Ebyte Electronic Technology Co.,Ltd.
User Manual
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Chengdu Ebyte Electronic Technology Co.,Ltd.
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suppress interference;
(3) The earth connection should conform to the national standard. If it is not guaranteed whether the ground connection
conforms to the national standard, it is recommended that the PE of this product is not connected to the ground to prevent
interference or even damage to the product.
3.2 Hardware connection of the first communication method
3.2.1 The first communication method: RS485
1) RS485 function
a. Configure product parameters;
b. Adopt RS485 remote transmission (pair transmission);
c. After the "RS485 transparent transmission" function is enabled, data transparent transmission is performed;
(For details, see "(2) Transparent Transmission" and "(3) RS485 Transparent Transmission Filtering" in the chapters
"Basic Product Parameter Reading and Change Writing" and "Mode Configuration Parameter Description").
(2) RS485 hardware connection
Wiring connection: RS485 wiring is very simple; you only need to connect product A of RS485 communication to A, and
B to B to complete the wiring. For the wiring diagram, see Figure 3-1 above.
3) RS485 parameter value options
a. Baud rate: 1200, 2400, 4800, 9600 (default), 14400, 19200, 38400, 43000, 56000, 57600, 115200
b. Check digit: None (default), Odd, Even, Mark, Space
c. Data bits: 6, 7, 8 (default), 9
d. Stop bit: 1 (default), 2
(4) Product RS485 hardware protection
This product RS485 has the capabilities of overcurrent protection, power surge protection, inductive lightning protection,
and EMC electromagnetic compatibility.
(5) RS485 bus wiring rules
a. If the transmission distance of the RS485 bus exceeds 100 meters, it is recommended to connect a 120Ω resistor in
parallel at the beginning and end of the RS485 network. Because with the extension of the transmission distance, the
echo reflection signal will be generated on the 485 bus network.
b. In industrial field applications, if the field interference source is very complex, there may be a high common mode
voltage between nodes. Although the RS485 interface uses a differential transmission method, it has the ability to resist
common mode interference. But when the common mode voltage is greater than +12V or less than -9V, it exceeds the
limit receiving voltage of the RS485 receiver, the receiver will not work, and may even burn the chip and equipment. At
this time, the RS485 optical isolation repeater should be used in the RS485 bus network to eliminate the influence of the
common mode voltage.
c. Since the RS485 bus transmits a pair of differential signals, the data transmission line between each device on the
RS485 network is best to use a twisted pair with an additional shielding layer, and the shielding layer should be reliably
grounded at one point.
d. In the simple application of the 485 bus, the bus-type topology wiring method is generally used. But in a more
complex system, the wiring construction of the bus topology is not only very cumbersome, but also wastes a lot of
