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BQ78350-R1: Query for communication protocol used in BQ78350-R1

6548808
Prodigy 10 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQSTUDIO, EV2400, BQ78350

HI,

I am working on development of software drivers for a host which is supposed to be connected to BQ78350-R1 over SMBUS lines. I have few queries which are as follows...

1) Technical reference manual of BQ78350-R1 states default address of this IC operating as slave with SMB Configuration register 7th bit set to 1(Fixed address) is  0x16/0x17. Considering this, I tried to communicate with this IC through my host controller and  there was no response from IC. upon scanning the bus for all possible addresses I found slave IC on 0XB (11 decimal). To verify my results I connected BQ78350-R1 IC through EV2400 and tried to Sniff packets communicating between IC and BQ studio IDE. Though IDE stated that chip was on 0x17,  I was surprised to see bqstudio communicating to IC over 0xB as IC's address over SMBUS. 

2) Query is about the sequence of data being read and written to IC. A simple voltage read command with PEC disabled  should have following sequence [address write] ,[command],Start, [address read], [voltage reading LSB], [voltage reading MSB],End. Again, sniffed data for voltage read  command over SMBUS shows one additional byte at the end I am not clear what does this byte specifies.

Ronak

        

  • +1
    TI__Genius 11535 points

    Hi Ronak,

    If you look closely at the picture you sent, it actually is sending to 0x16, the analyzer is just reporting it as 0x0B (it's shifting the address to the right 1 bit). Your picture looks like it is correct; it is sending a command and then reading back two bytes + the PEC byte. You can't disable the PEC byte on the gauge.

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Prodigy 10 points

    Hi Jessica. Thanks for the information.

    1) In the case for PEC I referred to datasheet please check snippet.

     

    2) I seriously doubt the address issue. why I am stating this is because I scanned for presence of slave by updating addresses in a for loop and I received acknowledge on 11th iteration. 

    -Ronak 

  • +1 in reply to 6548808
    TI__Guru* 81034 points

    Hi Ronak,

    The PEC is not required for the BQ78350, but BQStudio will always use PEC even though it is optional. BQ78350 will still accept communications with PEC.

    The address is correct (0x16). Like Jessica said, your analyzer is interpreting the address shifted by one bit. It seems your host and analyzer are ignoring the LSB (7-bit addressing vs 8-bit addressing). From a 7-bit perspective, the device address is 0x0B.

    Best regards,

    Matt