DSAB wiring conventions and standards

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  A Note from Dynon Avionics: The customer-submitted content on this page does technically represent best practices for RS-485 network construction.
  However, many the steps described below mainly benefit RS-485 that are more complex than Dynon's DSAB and SkyView Networks. 
  Dynon has determined that the steps below that go above and beyond the SkyView installation manual's requirements are not necessary for 
  robust DSAB and SkyView network operation. Dynon also believes that in troubleshooting situations, adding the below to a SkyView or DSAB 
  network will not improve or change network performance. That said, the below shouldn't adversely affect a Dynon network either.

Dynon's DSAB uses the 3 wire RS-485 standard as a physical media with their own proprietary protocol running on top of this physical layer.

Here is some good info to help understand the RS-485 standard: [1]

Here is some good info to help understand how to layout your DSAB wiring and how to interconnect it and how to guarantee the best noise immunity on your DSAB network: [2]


Some key points:

  • The DSAB network needs to be a contiguous bus with only two ends.
  • The two ends of the DSAB network need to be terminated with 120ohm resistors at both ends as close to the end of the line as possible. Only two resistors per network.
  • Star configurations of the DSAB network are not recommended.
  • Devices should connect to the DSAB bus with stubs that are as short as possible.
  • Long stubs or droplines are not recommended.
  • Only use twisted pair wiring. The ideal wiring would have an impedance of 120ohms.
  • Shielded twisted pair can be used but is not required. Ground one end of the shield only and ensure the cable has an impedance of 120ohms.
  • Ground each DSAB device using a common ground point since the common ground serves as the signal common for the DSAB network.

Example picture of a model DSAB bus with multiple devices connected (more devices can be added as needed):

DI23Fig09.gif