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DS90UB947-Q1EVM: Configuring GPIO as forward channel

Tony Gray
Prodigy 60 points
Part Number: DS90UB947-Q1EVM

I have a DS90UB947 EVM connected to a DS90UB948 EVM.  MODE_SEL0/1 are at defaults.  I'm trying to set GPIO0 to pass through to the deserializer.  On the 947 I set the GPIO register to output mode and high:

On the 948 I set the GPIO0 register to enable and remote enable:

When I check the GPIO0 pin on the 948 (J17.2), it's at 0V.  If I uncheck remote enable and set it high, it goes to 3.1V, so I know the 948 is capable of driving it high.  But for some reason the high setting from the 947 isn't being passed through to the 948.  I tired the same thing on GPIO2 to 3 and got the same results.

  • +1
    TI__Guru** 103215 points

    Hello Tony,

    If you want to pass a GPIO through from 947 to 948, then the 947 side needs to be configured as an input, not an output and you need to externally drive that pin high on the 947 side. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 60 points

    Thanks for the explanation.  I knew that if I made GPIO0 an input it, the physical pin state would be replicated on the deserializer board.  For some reason I thought that if I made it an output and then set it to a value, it would also get replicated.  For my testing I don't have a physical input connected to the GPIO pin on the serializer eval kit.  For now I can just set the pin state using the remote registers.