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BQ78350-R2-DEVICE-FW: SMBUS register reading problem.

Ferman
Prodigy 50 points

Part Number: BQ78350-R2-DEVICE-FW

Hi,

We are using Bq78350-R2 for one of our design, and mcu keeps communicating with IC continuously. Along one cycle of reading, almost 20 registers are read including "DAStatus 1". At the end of this cycle "DAStatus 1" register is read 4 times sequencially which have 42ms between each read. Despite there have never been any delay when reading any of register excluded "DAStatus 1", occasionally it takes 92ms to read "DAStatus 1" register. 

The frequency of occurance is variying between first cycle and up to thousandth cycle. I shared the ss for end of problematic cycle which shows logic analyzer results.

Figure1 -> First reading of "DAStatus1" register at the end of a cycle(5ms)

Figure2 -> Second reading of "DAStatus1" register at the end of a cycle(5ms)

Figure3 -> Third reading of "DAStatus1" register at the end of a cycle(5ms)

Figure4 -> Fourth reading of "DAStatus1" register at the end of a cycle(97ms)

Figure5 -> Delay duration between any two read attemp

Note: While transmitting and receiving SMBUS data, we use "SMBUS_FIRST_AND_LAST_FRAME_NO_PEC" setting, if it can help to solve the problem.

Thanks in advance

  • 0
    TI__Guru* 80453 points

    Hi Ferman,

    The BQ78350 is also communicating continuously with the BQ769x0 battery monitor to read voltage/current/temperature readings and status bits. If you use the SMBus heavily, it may not be able to respond quickly. Is the main issue that you are seeing a delay?

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 50 points

    Hi Matt,

    Strange thing is this is happining while reading "DAStatus1", not any other register. Each read request should be replied within 20ms for our system to work properly, otherwise it fires timeout error.  

    Is there any solution to overcome this delay, or is it somehow possible to detect if BQ78350 is busy with communicating AFE IC?

    Best Regards

  • 0 in reply to Ferman
    TI__Guru* 80453 points

    Hi Ferman,

    Unfortunately there isn't an easy way to detect if the BQ78350 is busy communicating with the AFE. 

    The AFE only updates the cell voltage measurements every 250 ms. The BQ78350 uses the cell voltages for gauging and for protections. Is it necessary for the host to also read these values frequently?

    Best regards,

    Matt