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Original question:

SN65HVD96: RS-485 Power Over Bus

SN65HVD96: RS-485 Power Over Bus

Sukhpal Singh
Prodigy 60 points
Part Number: SN65HVD96

Hi 

 I am developing a solution for Powerline communication. Study different Circuits, I stuck when I send a signal from  USB to rs485 Converter to my module it is not read any data on the slave side . when I check with MSO I find out that signal Transmitted, but the Differential signal was less them  200 millivolts. Then I study that I need an AC / DC square wave signal for communication when I send it through DC line the RS485  chip not read this differential signal.

So according to my investigation, I find either I have to generate a square wave power supply for communication over DC power. 

Reference Design from : 

**Using SN65HVD96 to Create a Power-Over-Data and Polarity Immunity Solution

regards

Sukhpal Singh

  • 0
    TI__Mastermind 25705 points

    Sukhpal,

    To transmit data over power line, you could separate data and DC power in different frequency domains by using inductors and capacitors. Therefore data and power don't interfere with each other although they share the same bus physically. The data need to be modulated (like Manchester code) or use tri-level signaling (like this reference design). The purpose is having a pure 'AC' signaling with a balanced DC bias. Please let me know if you have more questions about this interesting topic.

    Regards,

    Hao 

  • 0 in reply to Hao L
    Prodigy 60 points

    Hi Hao 

               thanks for your support . As you have guided me to study the Manchester Code and Tri-Level Signal I go through one video and also study a few notes from Google. Now i try to implement in controller coding and then show u my Scope output and I hope the concept which you have given to me help me in development.

    Suggest me  I have to couple this Tri-level signal at input or Output of SN65HVD96.  As output is coupled to DC line and I think that result in Attenuation of Signal.

    Regards

    Sukhpal Singh 

  • 0 in reply to Sukhpal Singh
    TI__Mastermind 25705 points

    Sukhpal,

    The tri-level signal are connected to the A/B pins of HVD96. You can refer to this app note for the details. http://www.ti.com/lit/an/slla336/slla336.pdf

    For RS485 signaling, you can refer to this design: http://www.ti.com/lit/ug/tidu993/tidu993.pdf

    Please let me know if you have more questions.

    Regards,

    Hao