RS485 Timing Protocol 2


In addition to the silence time detection I can actually simplify the protocol by demanding that each device send a EOT (End Of Transmission) sequence. As EOT for 1 is detected by 2 it can start sending or just send it’s own EOT. If we design EOT to be a small message with status we only need to use timing to detect failing devices. In this case timing is less critical and this is basically the same technique we use on SmartSPI.

rs485-xWith 1 byte status byte that would be 10 bytes that on 19200 baud is transmitted in ca 3.8 ms.

  •  AA : Start byte
  • DID: Device ID
  • SID : Stream ID
  • MID: Message ID
  • SEQ: Sequence Number
  • DL: Data length
  • CRC : 16 bit checksum

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