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BQ27421EVM-G1B: Gauge readings only update after battery insertion

Sean Starick
Prodigy 20 points
Part Number: BQ27421EVM-G1B


Hi,

I have the BQ27421 EVM and I am displaying readings as seen in the images. I have an initialisation function which sets the standard parameters as per the Quick Start guide (design capacity, design energy, taper rate, terminate voltage). 

I am currently using the default BIN low setting and keeping this pin low (although I have tried subcommand method). 

The issue is that I can only get full set of readings when I remove and then reinsert the battery. The problem being that my initialisation values are then lost and parameter values are defaulted. I get a partial set of readings after I initialise, ie voltage, average current, but a lot of zeros.

It seems as soon as I write to the data blocks, this disrupts the readings somehow. As far as I am aware, the only conditions I need to meet in order to get readings are that the BIN pin is low and the battery insertion detection flag is set.

Partial set of readings after initialisation.

Full set after Battery reinsertion, design capacity values etc defaulted.

Any help greatly appreciated.

Thanks,

Sean.

  • 0
    TI__Guru** 106050 points

    Hello Sean,

    This gauge is a ROM based gauge so all the parameters you program will be lost upon reset.

    Sincerely,

    Wyatt Keller

  • 0
    Prodigy 20 points

    Hi Wyatt,

    Thanks for your reply.

    Yes I realise this. What I am trying to achieve is to have the battery already connected, send the initialisation parameters to the device over i2c , and have the device give a full set of readings.

    At the moment this only yields the partial set of readings. and the only way I can get the full set is to disconnect/reconnect the battery, at which point I lose my settings as you've said.

    I'm wondering if there is a particular sequence I need to follow to trigger the readings after initialisation.

    Thanks,

    Sean.

  • 0 in reply to Sean Starick
    TI__Guru** 106050 points

    Hello Sean,

    If you perform a soft reset the gauge should take an OCV and correlate that to give the parameters that are currently set to 0 in your initial post. A soft reset should not clear any of your RAM and should only re-run a simulation for SOC.

    Sincerely,

    Wyatt Keller