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TMDSCNCD28379D: Connecting an I2C IO expander

Uri Garbi
Intellectual 285 points
Part Number: TMDSCNCD28379D
Other Parts Discussed in Thread: TCA6424A

Hello,

I am designing a PCB that connects to the TMDSCNCD28379D via the 180pin HSEC connector.

I need more GPIOs than what is available on the HSEC connector, and so I would like to add a port expander, and was looking at using the I2C interface (GPIOs 32 and 33). I am considering using TCA6424A for this to provide additional 24 IOs.

Few questions:

1. Any other recommendation?

2. The SDA and SCL lines, and the INTn signals of the TCA6424A should be pulled up to the Vcc of the host. However the HSEC connector provides no access to the 3.3V generated on the control card. Is it OK to pull up to a local 3.3V that I generate on my own PCB?

3. Is it possible to connect two TCA6424A chips in parallel on the same I2C port - one configured as ADDR=0 and the other as ADDR=1?

4. Is it OK to tie the RESETn of the TCA6424A to the DEVICE_RESET pin on the HSEC connector (this pin is asserted by the TMDSCNCD28379D control card).

Thanks

Uri

  • 0
    TI__Mastermind 38295 points

    Hi Uri,

    As a disclaimer, ControlCards are typically meant for evaluation use only and not to be used in an end system. I'm not saying you can't do it, just wanted to mention it. Onto your questions...

    1. There is a high density connector on the F2879D ControlCard you could utilize (J9) on the card for more GPIOs that what go to the HSEC connector.

    2. I'm not certain. Would likely be better to post on the TCA6424A forum for this.

    3. It looks like this is possible since it seems the TCA6424A can act as an ordinary slave device.

    4. Probably, but would be good to check with the TCA6424A team as well. Should check that the RESETn voltage on the TCA6424A matches the F28379D device XRSn voltage (VDDIO).

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    Intellectual 285 points

    Thanks Kevin.

    Understood.

    Regards

    Uri