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BQ34Z100-G1: Fuel Gauge EV2400 Communication no ACK

vincent Philippart
Prodigy 130 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: EV2400, , BQ34Z100, BQSTUDIO

Hi all,

I'm current testing a BQ34Z100-G1 fuel gauge on an system side EMS. The device is connected to an STM32 MCU. For stand-alone testing and calibration I'm using the EV2400 and de-soldered series and pull-up resistors to the MCU.

So far I verified the +4V supply outputs a voltage around 3.5V and the VREG is able to regulate to 2.5V. I'm however unable to connect with the EV2400 connected to the I2C port (PORT 2). No ACK is received. I updated the EV2400 firmware to the latest 0.28 release.

I can tell that the EV2400 is sending data correctly, SI looks to be okay too after removing the clamping diodes. I measured at VEN and found that it pulses irregularly (>5s) with 120ms width indicating that it's sampling slowly. I can't find any stange behaviour on start-up either.

Is there any obvious mistakes I'm missing and is there a place to look next?

Thanks!

See attached schematic below:

  • 0
    TI__Mastermind 42535 points

    Hi Vincent,

    You do need the i2c pullups for the comms to work. The ev2400 does not have internal pullups on i2c. Please reconnect them and your device should work.

  • 0 in reply to Batt
    Prodigy 130 points

    Hi Batt,

    Thanks for you reply, I will give this a shot and get back to you.I believe I tried external pull-ups before removing the +3V3 clamping diodes but I'll try this too.

    The EV2400 datasheet however describes 20K pull-up resistors hence my choice to remove them:

  • 0 in reply to Batt
    Prodigy 130 points

    Hi Batt,

    I changed the pull ups to 10k, pulled-up to REGIN. I also shortened the provided cable to reduce SI issues.

    The EV2400 is still unable to connect. The VREG also still seems fine and steady at 2.5V. From what I can tell it keeps sending NACK responses. We're able to communicate with the BQ34Z100 using the STM32 on another sample. For calibration however we'd like to use the EV2400.

    Battery studio does not autoconnect, after selecting device I can tell the battery studio connects for a second with the following frame:

    After a moment however it starts showing the following secequence repeatedly. After this the EV2400 just repeats it after a second or so.

    The frame from the STM32 looks as follows:

  • 0 in reply to vincent Philippart
    TI__Mastermind 42535 points

    That definitely looks weird. You are getting acks from the uc but the ev2400 is nacking it. Do you by any chance have another ev2400 that you can try this with? I'm out of ideas as to what is happening here.

  • 0 in reply to Batt
    Prodigy 130 points

    Hi Batt,

    Unfortunately not, this is the first time we're using this kind of calibration.

    The only reason I can think of is that is "busy". Could it be locked in some kind of state, is there any way to check the state of the BQ34Z100?

    Regards,

    Vincent

  • 0 in reply to vincent Philippart
    TI__Mastermind 42535 points

    Hi Vincent,

    Even if the bq34z100 is busy, a prolonged computation in the IC that exceeds preset timers would cause a WD reset and then enable comms anyway once the comms interrupt gets priority.

    Your schematic looks OK to me. One suggestion I have is to see if you are able to get comms on the ev2400 with a bq34z100 evm. If you do, then it may be your line terminations at the host (on the STM which work better for your application) compared to the ev2400.

  • 0 in reply to Batt
    Prodigy 130 points

    Hello Batt,

    We've fixed it. I tried on several boards; stangely enough it never seems to autoconnect on any of the boards. However when I push a command (through BQStudio) such as "CONTROL_STATUS" regardless it suddenly connects and behaves like expected.

    Since the EVM is just for debugging/calibration I didn't put more time into analyzing it.

    On another note I had to update the .bqz file from another thread to get the calibration to work.

    Thanks for investigating!

    Regards,

    Vincent Philippart