Modbus connection

The Modbus protocol is used in automation devices, including Smart Home systems. Like any other protocol, it defines the rules of data transfer between devices.
According to this protocol, the automation system must consist of one master device and up to 248 slave devices. This configuration and the limited number of slave devices are among the disadvantages of the Modbus protocol. However, it should be understood that this protocol is the standard for data exchange between devices in industrial automation.
Each Atom series controller has an RS-485 interface with the implementation of the Modbus protocol, so it can control any device that has the ability to work with this protocol. Since this protocol was created open from the beginning, thousands of devices have been developed to work with it.

Here are some of them:● air conditioners;● various industrial and household meters;● sensors;● thermostats;● convertors;● lighting control devices;● access control devices;● some models of motorized cornices.

Devices on the RS-485 bus are connected to the controller via a twisted pair cable, which significantly improves interferences immunity and is a prerequisite for connecting all Modbus devices. The use of twisted pairs allows you to create lines up to 1,200 meters long, which meets almost all the needs of home automation.
It is also important to ensure sufficient distance of information cables from power cables. Shielded cable is often used to improve interferences immunity.

Important! The shield of the cable must be connected to ground on one side only.

A prerequisite for reliable operation of the RS-485 interface, according to the standard, is the presence of matching resistors at both ends of the bus. These resistors are included with the Atom controllers.
Bus topology - linear, with a minimum length of branches to connect peripherals.


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