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TCA9544A: Request For Clarification About Sending I2C command Simultaneously

Nitheesh kumar R
Prodigy 130 points

Part Number: TCA9544A
Other Parts Discussed in Thread: TCA9546A, TCA9543A

Hi,

 

We are evaluating the TCA9544APWR for a multi-channel I²C architecture.

The host controller is connected to the upstream I²C interface of the TCA9544A. The downstream side consists of four independent channels, with each channel connected to one camera via its I²C control interface.

Our main requirement is to control all four camera I²C channels simultaneously, particularly for synchronized control of the cameras' motorized lenses.

Could you please clarify:

Can all four TCA9544A channels be enabled simultaneously?
If all four channels are enabled, can the host transmit the same I²C command to all four cameras simultaneously (broadcast)?
If simultaneous transmission is not supported, what is the minimum practical delay between the same command being sent to the four cameras?
Is there any recommended configuration or method using the TCA9544A to achieve the closest possible synchronization across all four camera I²C channels? 

Regards,

Nitheesh

  • 0
    Guru 327110 points

    The TCA9544A allows to enable only a single channel. To be able to enable multiple channels at the same time, you need a switch like the TCA9546A.

    With the TCA9546A, and with the four cameras all having the same I²C address, it is possible to send read/write transactions to all of them. This makes sense only if the data sent and received is exactly the same.

  • 0 in reply to Clemens Ladisch
    Prodigy 130 points

    Hi,

    1. Broadcasting the same command to multiple channels:
    We understand the TCA9546A's channel-select register allows any combination of the four channels to be enabled at once (unlike a traditional one-at-a-time mux), and that this lets us broadcast the same command to multiple channels in a single transaction. Can you confirm this is correct?

    2. Sending different commands
    If each camera needs a different command, do we need to enable one channel at a time and send them one after another?

    3. Same address on different channels
    Since each channel is isolated until it's enabled, can we connect four devices with the same I2C address — one on each channel — without any address conflict?

    4. Enabling channels in different groups
    Can channels be enabled in different combinations depending on what we need? For example:

    Enable Channel 2 + Channel 4 together to send one command
    Then switch to Channel 1 + Channel 3 together to send a different command

    Regards,

    Nitheesh

  • 0 in reply to Nitheesh kumar R
    TI__Mastermind 28345 points

    Hello Nitheesh,

    1. Yes, the TCA9546A is what we call a switch. You can have multiple channels enabled at the same time. 

    2. Yes, that is correct.

    3. Yes, because each channel mux has its own unique address. 

    4. Yes, that is possible.

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    Prodigy 130 points

    Hi,

    Thanks for your response.

    Is a two-channel version of the TCA9546A available?

    Also, please confirm whether the TCA9544A has any address conflict issue. We are facing an address conflict issue with our existing board.

    Is it possible to connect I²C devices with the same address to different channels of the TCA9544A and TCA9543A?

    Regards,
    Nitheesh

  • 0 in reply to Nitheesh kumar R
    TI__Mastermind 28345 points

    Hello Nitheesh,

    Yes, the TCA9543A. 

    How are you implementing and communicating to the TCA9544A? What signals are you sending? 

    Yes, even though the target devices have the same address, each mux channel has its own unique register.
    Resulting with the I2C targets to have different addresses.

    Thanks,

    Nir