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BQ78350-R1A: Random NACK its own address

Oscar Perez
Prodigy 45 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ78350, EV2400, BQSTUDIO, BQEVSW

Hi All,

I have searched every post to date regarding the BQ78350-RXX looking for an answer. I'm honestly in dire need of assistance with this issue.

The BQ78350 does not always ACK its own address with communication with a host controller using the EVM hardware. Interestingly enough, it always ACKs when using the EV2400.

My set up:

nRF52840 @ 3.3V

Vh = 2.5V

Vl = 0V

F = 100KHz (my scope says otherwise because the measure isn't set up right..) 

I wait ~2ms between each transaction

And wait 1 second between complete scans

The problem:

The BQ78350 did not ACK its own address.

Sequence: 

S 0 0 0 1 0 1 1 W NACK P

Most transactions go without issues but it is always a random NACK every few seconds. This is quite not ok with a medical product. 

There has to be a cause because the EV2400 does not appear to have this problem but I cannot see anything wrong with this.

Any help would be  gracefully accepted.

OscarP

  • 0
    TI__Guru 57697 points

    Hello Oscar,

    Random Nacks are present with EV2400. If you log using Registers window in bqStudio or SBS windows in bqEVSW, you will see missing data.This is because of Nacks or other errors.

    All systems are supposed to retry in case of Nack. The Nack retry and PEC usage is primarily to protect the system from noise. The bq78350 will Nack when it is busy. Sometimes it can also time-out the transaction.