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TCA9548A: Unable to communicate

switch
Expert 2385 points
Part Number: TCA9548A

Hi ，

I encountered the following problems while using TCA9548：

1，When the IIC bus on the expansion side of the TCA9548A(SDA,SCL）is hot-plugged, the TCA9548A cannot communicate with the microcontroller properly.

2.The microcontroller and the expansion chip TCA9548A can communicate normally when the experiment is left for a long time, but cannot communicate normally with the equipment at the expansion end.

  Below is the waveform captured by the oscilloscope (SDA cannot be pulled down completely, sometimes this step exceeds 600mV):
  • 0
    TI__Mastermind 22835 points

    Smith,

    Thanks for reaching out! Let's try to figure out what is going on.

    It sounds to me like you're saying that you are able to control the TCA9548A normally before a hot-plugging event, but it stops operating when the external/expansion board is connected to the main board with the microcontroller. Please allow me to ask some clarifying questions so that I can ensure I understand your situation.

    Is the TCA9548A powered during hot-swap connection of the expansion board? Also, is the TCA9548A on the main board or on the expansion board?

    I am assuming that the microcontroller is connected to pins 22 and 23 of the TCA9548A. Are any channels of the TCA9548A already connected/enabled when hot-swapping occurs?

    Thank you for including an image of the oscilloscope. The 600 mV VOL should still be a satisfactory low voltage, as the low-level input voltage for the device is 0.3*VCC. I am unable to make out the specifics of the communication, but I do not see any major issues with the waveform in this view.

    If the device is powered with the expansion card already connected, is the TCA9548A able to communicate? In other words, is the device able to work at all with the expansion card connected?

    Lastly, you said "TCA9548A can communicate normally when the experiment is left for a long time," but I am not sure what this means. Would you mind providing some additional detail about what you are seeing here?

    Best,

    Danny