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PCA9548A: Interfacing with devices needing repeated start

Lukasz Przenioslo
Expert 2630 points
Part Number: PCA9548A
Other Parts Discussed in Thread: BQ34110,

Hello there,

I would like to use the PCA9548A chip in order to talk to 8 separate (normally unaddressable) BQ34110 chips. When talking to this chip using I2C, one has to utilize rpeated start functionality (slua790):

Will this not interfere with the PCA9548A, meaning, will it not disable the multiplexed channel at this time?

I would appreciate all help regarding this issue.

  • 0
    TI__Guru 62920 points
    Hi Lukasz,

    The channel selection will only change if a write is made to the PCA9548A's address. Other I2C transactions that address other slave devices would not have an effect on PCA9548A. Using repeated starts should not affect the channel selection, then. Let me know if you have any further questions or if I've misinterpreted what you are asking.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Expert 2630 points
    Hello, thank you for answer.
    So If I understood correctly, everything that addresses the multiplexer, is obtained by it. Everything that addresses something else, is passed throught set channel?
  • 0 in reply to Lukasz Przenioslo
    TI__Guru 62920 points
    Lukasz,

    That's not quite accurate. Instead I would say that any I2C transactions will be passed to any active channel. (This happens immediately; the transactions are not stored or re-forwarded in any way.) If that I2C command references the PCA9548A, then the PCA9548A will take some action based on it. If the I2C command references any other address, the PCA9548A will ignore it.

    Max