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PCA9517 Review

Karen Morrell-Emanuel
Prodigy 165 points

Could you please forward my question below regarding the Texas Instruments PCA9517DGKR I2C Bus Repeater to the right folks over at TI?

 

Is there something wrong with the way I have the Texas Instruments PCA9517DGKR I2C Bus Repeater hooked up (see schematic below)?  On the B side of the repeater, I have no I2C devices attached.  On the A side, I have a processor (with 10K pull ups on SCL and SDA) and four I2C devices each at different addresses.  When the repeater is installed, the processor cannot talk to any of the I2C devices.  As soon as the repeater is unsoldered on the board and removed, the processor can talk to all four I2C devices with no problems.  The repeater is hooked up as shown below.

 

Are there any known issues/errata with the PCA9517DGKR I2C bus repeater?  Perhaps, it is getting confused as to which side is the master when no I2C devices are attached to the B side.

 

 

PCA9517.docx
  • 0
    TI__Genius 9085 points

    I don't understand. There are no devices attached to the B side? How is this being used?

    This device does not differentiate between master and slave devices. It only propagates logic LOWS or allows the lines to be pulled-up to the respective VCCS if there is no active driver. If there is nothing connected to the B side, maybe it thinks that the B side is being driven LOW, so it is holding the bus LOW and not allowing communication.

    I think a more complete schematic could be helpful. I only see our device, and none of the other devices, so I am not sure I have an accurate understanding of the system.