1. Core Function
Signal conversion: USB (single-ended signal) cannot directly drive DMX devices, and RS485 (differential signal) is required to achieve anti-interference long-distance transmission (up to 1200 meters).
Protocol carrying: RS485 is used as the physical layer to transmit DMX512 data frames (250kbps), without parsing the protocol, only ensuring stable data transmission.
Multi-device support: RS485 supports bus topology and can connect multiple DMX devices in parallel (up to 32 loads).
2. Key features of RS485
Differential transmission: Data+/Data- twisted pair offsets common mode interference and is suitable for stages with complex electromagnetic environments.
Half-duplex communication: matches the DMX512 master-slave architecture (controller sends, device receives).
3. Workflow
USB chip (such as FT232) converts to UART signal → RS485 driver chip (such as MAX485) converts to differential signal → XLR output to DMX device.
4. Notes
Terminal resistance: A 120Ω resistor should be added between Pin2/Pin3 of XLR to prevent signal reflection.
Wire selection: Shielded twisted pair (such as Belden 9841) improves anti-interference ability.
