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Original question:

TI BQ27421 gauge: I2C command waiting time

BQ27441-G1: BQ27441 --- I2C command waiting time

_pA89
Prodigy 30 points
Part Number: BQ27441-G1

"For read-write standard command, a minimum of 2 seconds is required to get the result updated. For read-only standard commands, there is no waiting time required, but the host must not issue any standard command more than two times per second. Otherwise, the gauge could result in a reset issue due to the expiration of the watchdog timer. "

1. Looks Vague  -- Should These Statements be  Taken  "Seriously"? 2 Seconds Sounds Big Value @ f=100KHz

2. Cant Internal Insight (Architectural Diagrams, State Diagrams be shown e.g. Like bq27441- Figure 2-1. Power Mode Diagram of Technical Reference Manual) for Communication Engine instead of Raising All these Confusing Questions Below (One Proper Diagram Would Have Clarified Many Doubts)
https://e2e.ti.com/support/power-management/f/196/t/538858?TI-BQ27421-gauge-I2C-command-waiting-time------https://e2e.ti.com/support/power-management/f/196/p/538858/2033032?pi317195=1-----https://www.avrfreaks.net/forum/bq27441-g1-battery-fuel-gauge-i2c-shenanigans-----

3. Where Can I Find More Insightful Information on I2C Engine in BQ27441-IC (which can Clarify Doubts raised by Half-Half Information provided in Datasheets, Reference Manuals...)

  • 0
    TI__Guru* 76230 points

    hi

    1. yes

    2. You can reference the bq27421 dcoi. The i2c engines on both devices are the same.

    3. See 3 above.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 30 points
    Better Answer ...
  • 0 in reply to _pA89
    TI__Guru* 76230 points
    The gauge only does updatesparamtes like voltage or current once per second. It is redundant sending commands more than once a second. For changing parameters of the gauge where you have to do a read-write function 2 secs is needed to ensure the parameter updates before reading back the value.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 30 points
    Hi Onyx, Thanks For the Reply ...
    I Understand "Fuel gauging and data updated every 1s--NORMAL STATE" from bq27441- Figure 2-1. Power Mode Diagram of Technical Reference Manual -- Hence You Claim is Redundant Sending Command More than Once a Second.

    But I Don't Understand " Otherwise, the gauge could result in a reset issue due to the expiration of the watchdog timer."--From Datasheet --- The Gauge Could Simply Send the Values not Updated Instead of Resetting Itself ...? Can You Explain why this happens ....
  • 0 in reply to _pA89
    Prodigy 10 points

    I too would very much like a clear answer to this please .

    Of note is that the example code in SLUA801 (Gauge Communication) makes no attempt, nor mention of it being necessary, to restrict the commands to 2-per-second to avoid WDR.

    The big issue here is that with such a restriction, it takes approximately 15-20 seconds(!!) to initialize all the gauge registers. Crazy.