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Design and Evolution of Lighting Protocols

BSP

In the late 1970's Siemens was producing the B40 product line. They featured a protocol called Bit Serial Protocol (BSP) for transmission of data to lighting devices.

Layer 0

BSP uses the standard serial transmission via rs422. rs422 is roughly the same as rs485. BSP is asynchronously clocked with 250KBit. The Sender (Master) issues the clock rate via a clock line. Transmission uses the 8N2 schema.
The connector has 5 pins assigned with symetric clock and data and gnd. (+clock, -clock, +data, -data, gnd)

Layer 1

Transmission is divided into frames of up to 512 bytes. Valid data bytes have values from 1-255. Value 0 is invalid and used to mark a new Frame.
The frame layout is a follows:

  1. Frame Start indicated by 3x 0
  2. Up to 512 Bytes (value 1-255)

DMX512

To remind you, here is a quick summary of DMX512. Serial transmission via rs485 with 250KBit with 8N2. Data organized in frames with up to 512 bytes. A frame start is indicated with 88 μs break (low) followed by 4 or 8 μs mark (high). Then a config byte follows (normally 0) and up to 512 data bytes.

Comparison of BSP and DMX512

comparision of protocol timing

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