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My bq77PL900 is powered up but won't communicate over the serial communication bus. What could be wrong?

WM5295
Guru 54715 points
Other Parts Discussed in Thread: BQ77PL900

The serial interface internal supply and pull-ups are provided by the VLOG input
to the device. If VLOG is missing, external pull-ups on the I2C lines will
not make the device communicate. 

  • Check that VLOG is present on the IC. 
  • On the EVM, check that the shunt is properly installed for the desired
    logic voltage.
  • Prodigy 10 points

    bq77PL900 EVM was in host mode and the usb cable got disconnected.  Now the EVM will not communicate with the software.  VLOG is set correctly, all internal voltage regulator outputs are good.  The BQ77PL900 appears to be working fine in standalone mode but will not communicate with software.

  • in reply to Richard Remmers
    Prodigy 100 points

    Dear,

     

    i have same issue in our Evaluation Board and Vlog is short to 5V (Vreg1 ) for EV2300 ,

    Do you have any  ideal for which block diagram or pin to be relative the coummication  ?

    Thks,

    Leung

     

  • in reply to Wing Leung Wong
    TI__Guru 54715 points

    Apply a battery and pack voltage sufficient for both regulators to be up. VLOG must be tied to one of them, Vreg1 as you indicate is fine.  XRST should be high.  A host should then be able to communicate with the part through the SCLK and SDATA lines.  The device block diagram in the datasheet and the EVM schematic in may be helpful.

    If the software does not respond, check the ev2300 driver installation. There are several comments in the community forum. Check the cable installation for the proper connector insertion (I2C) and loose or damaged wires. Confirm the SDATA and SCLK signals arrive on the board and at the chip, the signal swing is sufficient and the protocol is intact.