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I2C Address conflict with BQ27500 and serial eeprom

Joe Reagan
Prodigy 60 points
Other Parts Discussed in Thread: BQ27500

Hello,  I am using the BQ27500 and a serial eeprom.  The address of the BQ27500 is 0xAA.  the address of the eeprom is 0xA0.  I cannot get the TI EVSW software to communicate properly to our PC board because of the EEPROM.  If I remove the EEPROM or lift the SDA leg it works.    the BQ27500 EVAL board will not work right if an EEPROM of any adress 0x1010xxxx is used.

I wonder why TI would have chosen an address of 0xAA which has the same upper control part of 0x1010 as a common eeprom.  And it seems to be causing an address conflict with TI EVSW software and the EV2300.

Does anyone know if this is an issue with the EVSW or is it to be expected based on how an EEPROM will respond?

I really need to use an EEPROM and like the BQ27500 as well.

Thanks

Joe

  • 0
    TI__Prodigy 480 points

    Joe,
     
    The 7 MSB's are all equal in determining the device address.  The upper nibble being the same is not constraining the use.  Actually, the symptom you describe is that the EEPROM is responding when it should not.  Try lifting the SDA connection to the bq27500 instead of the EEPROM and see if there is any activity on the SDA line from the EEPROM when the EV2300 tries to address the gauge at 0xAA.  Some EEPROMs have the option for setting the device address differently by a logic 1 or 0 on some of the IC pins.  You might check how the EEPROM is configured.  I am not aware of this issue from other customers using this part.  We have several gauges that use the 0xAA/0xAB device addresses, that have been in production for many years without complaint about this issue.
     

  • 0 in reply to TravisN
    Prodigy 60 points

    Thanks Travis.

    I always thought that the entire 7MSBs are what determined the device address too.  In the EEPROM data sheet I do see that the device will ACK when the upper control word of 1010 (0xA) is put on the bus.  Then apparently the next 3 bits allow selection of 1 of several other EEPROMs.  I believe you that if I lifted the BQ27500 leg(though this is gonna be impossible without ruining it) the EEPROM would ACk.  I could always hook up an EEPROM directly to the EV2300 and use I2C to prove this also.  It seems to me that my code works with both parts on the board, though I have by no means had perfect communication with the part. So maybe it is ACKing when its not supposed too, but I am getting lucky.

    The bottom line though is even if my code works, I need to use the EVSW TI software for our system.  And as of now it will not work if i keep this EEPROM on there.  Do you know of one of the eeproms that allows the address selection?  As of now I have not been able to find one.   Do you have any other recommendations?    Perhaps some other customer is using such an eeprom successfully with the BQ27500.

     

    Thanks,

    Joe