1. Overview
The dual bus system is mainly divided into two types: modulation type and carrier type. The carrier type requires a master station, which costs around 40 to 50 yuan. Traditional PLC power line carrier solutions are relatively complex, with costs ranging from 10 to 50 yuan. In systems with fewer nodes, especially point-to-point communication systems, the cost-effectiveness is very low. In contrast, the direct current carrier type dual bus solution does not require a master station, and the bulk cost of a single chip is less than 2 yuan, providing exceptional cost performance.
2. Content of This Article
This article will use the XM2BUS direct current carrier dual bus chip XF2485 as an example to explain its application and principles.
3. Introduction to XM2BUS Carrier Type Dual Bus Chip XF2485
The XF2485A is an RS-485 transceiver power IC with built-in On-Off Keying (OOK) modulation and demodulation functions. By modulating data onto existing power lines, it enables simultaneous power delivery and data communication over the same pair of wires, significantly reducing system costs.
Its bus power supply current is 12A, with non-polar wiring, allowing both communication and power supply to be addressed simultaneously; the bus power supply range is DC 10-90V (for >90V, adjust the external capacitor voltage rating), and the communication distance is 500 meters.
4. System Principle Block Diagram
The XF2485 communication and application are very similar to RS-485. All MCUs in the system are peer-to-peer, with bus power supply and bus power extraction isolated through inductors, achieving isolation from power supply interference and load interference.
5. Explanation of Communication Schematic
The Pin4-AO and Pin7-BO of the XF2485A chip can directly send carrier signals to the bus through capacitors C1 and C5; the bus carrier signal is received and decoded by the chip through capacitors C6 and C10 at Pin6-A and Pin5-B. When there are fewer bus nodes and lighter loads, and for short distances, carrier signals can be sent directly through AO and BO, such as in 1-to-1 communication with a load of 300mA over a distance of 10 meters, which is comparable to communication within the device.
If there are more nodes, then Pin4-AO and Pin7-BO can strengthen the carrier signal through push-pull transistor circuits U1 and U2, achieving longer distances and accommodating more nodes, such as 24V, 10A, with 32/64 nodes.
6. Applications of Dual Bus XF2485
The XF2485 parameters are very close to RS-485, and the two-wire non-polar communication facilitates wiring. There is an improvement in wiring topology tolerance; although it is recommended to use a daisy chain wiring method, there is no need to worry about communication being affected if the actual construction does not follow the standard daisy chain method. Therefore, in traditional 485 applications with baud rates ≤ 9600bps, it can be directly replaced, such as in stair lights, lighting, sensor acquisition, building automation, factory automation and control, HVAC systems, electrical appliances, and power grid infrastructure.
7. Physical Display
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XF2485 LED strip solution (flicker-free)
XF2485 development board (replacing 485, non-polar, power + communication)
