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TCA9554A: direction of TCA9554A sometimes can’t be changed

Molly Huang
Prodigy 310 points
Part Number: TCA9554A

Hi Team,

When we using our TCA9554A.

We saw one situation that the direction of TCA9554A sometimes can’t be changed(tested on the same board).

It would keep 0xFF(Input) but what we need is 0x00(output)

Did your team have ever seen this situation before or any suggestion? Thanks.

  • 0
    TI__Guru 62910 points
    Hi Molly,

    There may be an issue with the I2C communication that is needed to properly configure these registers. Can you please capture the SDA and SCL waveforms when you are writing the 0x00 value and when you are reading back the 0xFF value afterwards so that we can check to see whether there are any issues?

    Also, you mentioned that this issue only happens sometimes. Does that mean that other times the port configuration is working properly? In which configurations does the issue show up?

    0xFF is the default value for the configuration register; is it possible that the device was reset/power cycled? This could happen if VCC falls to ~1 V. Could you please verify that VCC remains at the intended voltage level?

    Regards,
    Max