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AFE882H1EVM: HART TX always enable

Aarti Pamnani
Prodigy 40 points
Part Number: AFE882H1EVM
Other Parts Discussed in Thread: AFE882H1,

While giving the power to AFE882H1 from USB, everything works as expected 
like HART Mod is disabled while the demod is enabled 

but we have tried giving the power to AFE882H1 from our microcontroller and device is behaving very weird 
like HART OUT always transmit the mark signal also DAC is giving unexpected data even after setting the DAC_DATA register 

Can you please help us out.

Thanks,
Aarti

  • 0
    TI__Guru* 93945 points

    Aarti,

    The HART output FSK is enabled in response to /RTS being high. When /RTS is high, you will see the FSK on the MOD_OUT pin. 

    Have you checked to see if the microcontroller and device have a common ground? Do the supply voltages match? I think this might be a connection issue, so it might help to have a copy of your circuit. Are you able to send a copy of your schematic?

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 40 points

    Joseph,

    the HART output FSK is enabled in response to /RTS being high. When /RTS is high, you will see the FSK on the MOD_OUT pin. 
    We checked it on scope, RTS was low(0V)

    Have you checked to see if the microcontroller and device have a common ground?
    Yes, the microcontroller and device have a common ground.

    Do the supply voltages match?
    Yes, getting the power from main board, IOVDD is at 1.8V and PVDD is at 3.5V.
    removed the jumpers j26 and j27

     Are you able to send a copy of your schematic?
    Currently we do not have schematic ready with us we are working on AFE882H1EVM.


    after these connections we see continuous transmission on HART_OUT.

    Regards,
    Aarti

  • 0 in reply to Aarti Pamnani
    TI__Expert 4330 points

    Hi Aarti,

    Based on the datasheet diagram, if RTS is low and nothing is in the device's queue to be transmitted, the device will output a repeating Mark transmission:

    If a message is queued, the device will modulate the message. Once finished, it will restart repeating the Mark transmission.


    As for the unexpected DAC data, can you provide more information about your register configuration or the behavior you were seeing?

    Thanks,
    Lucas