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DS90UB947-Q1: I2C issue

Kevin Xiong
Expert 2340 points

Part Number: DS90UB947-Q1
Other Parts Discussed in Thread: DS90UB928Q-Q1

Hi,

I use DS90UB947-Q1 as I2C master and DS90UB928Q-Q1 as I2C slave. They communicate with each other through I2C. When the master sends a command to the slave, it receives ACK signal with 400us delays. I suppose that the delay is so long. Please see the attachment for details. My questions are:

1. What reason is for the long delay?

2. How to resolve this issue?

Thanks.

Kevin Xiong

  • 0
    TI__Mastermind 25955 points

    Hi Kevin,

    Thank you for sending the I2C transaction on the logic analyzer.  Looking into the 400 us delay.  Please expect an update tomorrow.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points

    Hi Kevin,

    I don't see a 400 us delay here caused by the FPD-Link interface.  At 0.4 ms the command from the master i2c device is sent and then relayed over FPD-link to the slave device.  The slave device then takes until 0.9 ms to respond.  The response is then sent back over the FPD-Link interface and to the master.

    The time between the cursors in the image above is the time from when the message is received by the slave device and response from the slave device is formed, prior to traversing the fpd-link interface.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points

    Hi Kevin,

    Haven't heard from you in a while - hopefully no news is good news and the issue is now resolved.  If so, to help enable others that may have the same question find the correct answer, please press the green 'this resolved my issue' button.

    If not, please let me know what other issues related to the original question remain.

    Sincerely,
    Bryan Kahler