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I2C command simultaneously to multiple slaves

Gregg Myer68
Prodigy 10 points
Other Parts Discussed in Thread: TCA9548A

I have an application where we set up a known pressure, then using a PCA9518DW, we give a command 'calibration' to multiple sensors.  Since the vacuum can drift, we would like to send one command to all sensors at the same time by enabling all I2C ports.

But what happens to the ACK bit at the end of the command.

 - Would it be possible to receive a NACK from one of the sensors? 
 - Would you be able to tell when all the Sensors responded?

  • 0
    TI__Expert 5140 points
    Hi Gregg,

    Can you send waveforms of your issue, so that I may better support this.

    In the meantime, here's some info about your application. In the event that you are only Sending information to the slaves (not having the slaves respond) then there should be no issue with the slaves ACKing. However, in the event that you have information from the slaves coming back to the PCA9518B, then you may not be able to communicate properly.

    You can receive a NACK from the sensors, but it'll most likely be ALL of the sensors NACKing.

    The sensors will respond by ACKing.

    Do you need the buffering aspect of this device? If not, I would like you to look into TCA9548A, an I2C switch, for this application as this may fit it better. Also, another thing to keep in mind if you're considering switching to this device is that this is I2C controlled.

    Thanks,
    Siby