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SN65HVD75: The design was not Communicating

Sakthi prakash
Prodigy 100 points
Part Number: SN65HVD75

Here i have attached my reference design Which taken from Ti Water Meter Design.

I made connection based on this design & Try to communicated the "Modbus RS485" Communication based Energy meter it was not giving any reply in "Hercules"

But When i try to Communicate that meter With USB to RS485 Converter it reply in Hercules.

Please Help me to solve this Problem.

  • 0
    TI__Guru 62920 points

    Hi Sakthi,

    For this design, when the "D" pin is high the "DE" pin will be low (due to PNP inverter stage) and the driver will become disabled.  So, you would need some external pull-up resistance on the "A" line and pull-down resistance on the "B" line to create a differential "high" level on the bus.  Could you try introducing these to see if communication works properly?  If that doesn't work, I'd recommend probing the various D/R and A/B pins at each side of the link to identify if there are any other hardware-related issues.

    Regards,
    Max