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TPL1401: I2C Read Sequence

Sam Ting
Expert 3660 points
Part Number: TPL1401


Hi team,

In the read mode, my customer can read the registers through the broadcast address 0x8E, but cannot read the registers through the general address 0x90. However, the broadcast address cannot be used for reading from datasheet section 7.5.5. Could you help confirm it? Thank you!

Best regards,
Sam Ting

  • 0
    TI__Mastermind 42273 points

    Hi Sam,

    What does the customer have A0 (pin 1) connected to? In addition, the I2C address should be 7 bits plus the R/W bit which should be 1 for reading. The total address byte would be 0x8F for the broadcast address or 0x91 for the general address if A0 is grounded.

    Can you ask the customer to confirm the A0 connection and send a scope shot of the I2C read sequence so we can verify the address. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    TI__Expert 3660 points

    Hi Katlynne,

    Yes, the A0 is grounded though 10k resistor. The SW engineer has confirmed the R/W bit is 1 for reading.

    But the questions is why he can read the registers through the broadcast address 0x8F, but cannot read the registers through the general address 0x91; In datasheet section 7.5.5, the broadcast address cannot be used for reading, but actually he can read it by broadcast address only.

    Sorry, we can't get the scope shot in lab due to WFH now. So we're trying to apply an EVM to check if any problems from hardware. Thanks for your support!  

    Best regards,

    Sam Ting

  • +1 in reply to Sam Ting
    TI__Mastermind 42273 points

    Hi Sam,

    I believe the datasheet says read is not supported with the broadcast address because the broadcast address is meant to be used with multiple TPL1401s that are using different general addresses based on their A0 value. I tested this with a TPL1401EVM and I was also able to read with the broadcast address, but there would be an issue if there was another TPL1401 also trying to send data back. If A0 is grounded then the TPL1401 should still respond to a read with the general address. 

    Is the customer able to write with the general address, or have they also been using the broadcast address? Can you ask them to try reading and writing with A0 connected directly to ground? 

    Thank you,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    TI__Expert 3660 points

    Hi Katlynne,

    Yes, the customer is able to write with general or broadcast address. Since there is only one TPL1401 in the application, they accept to read the registers with broadcast address. Thanks for your support! 

    Best regards,

    Sam Ting