BQ35100EVM-795: 'Negative' Current on bqstudio?

craig

Part Number: BQ35100EVM-795
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Hello,

I have the the bq35100evm connected with bqstudio. I've coded much of the algorithms myself and have recently shifted to utilizing bqstudio to aid in debugging.

My test setup is the bq35100evm connected with the ev2400 interface adaptor and a power supply being fed to bat+ bat- to simulate a battery.

I calibrate the volage as an open circuit (pack- not connected), this is the only way I can get a reasonable calibrated reading-Is this correct?

The current is show the right value (the value displayed on my power supply), BUT it's negative, which appears to be opposed to whats in the reference manual.

Is the negative sign addition Just GUI additions and the register value is actually positive (and vice versa)?

2 months ago

0 Evan 2 months ago

TI__Genius 12215 points

Hi,

Yes, this is the best way to calibrate the gauge.

Please read the CC Gain value, if it is negative, flip it to positive.

Regards,

Evan

0 craig 2 months ago in reply to Evan

Intellectual 490 points

Does the sign matter? I used the cc calibration and the board offset calibration. Surely those would invert the sign without me having to.

0 Evan 2 months ago in reply to craig

TI__Genius 12215 points

Hi,

A negative CC gain will result in a negative current.

Regards,

Evan

0 craig 2 months ago in reply to Evan

Intellectual 490 points

Evan thank you for replying. I'm familiar with gain. I'm computing a positive gain and saving it to data flash. So I'm confused as to why its coming back negative. What byte correponds to the signed value? byte 2?

I've checked my algorithm implementation against a known input/output and it checks out.

Is the gain sign abitrary? Will it have any deleterious effects?

0 craig 2 months ago in reply to Evan

Intellectual 490 points

How do I flip the sign?

0 craig 2 months ago in reply to Evan

Intellectual 490 points

Heck. The range shouldn't even extend to a negative value according to the documentation...So its bewildering because bqstudio is showing a negative gain...Weird.

Can a TI official clarify?

0 Evan 2 months ago in reply to craig

TI__Genius 12215 points

Hi,

Please allow me sometime to look into this.

Thanks,

Evan

0 Evan 2 months ago in reply to Evan

TI__Genius 12215 points

Hi,

Craig, I believe there was an error in calibration, please share your .srec and I will try to recreate the issue on my end.

Regards,

Evan

0 craig 2 months ago in reply to Evan

Intellectual 490 points

Evan,

Nick Richards here indicates that its negative, do you not believe this to be the case?

I can provide a .srec, but when i calibrate with my own code or through the bqstudio gui I still get a negative value.

0 Nick Richards 2 months ago in reply to craig

TI__Genius 17876 points

Hello,

Today's a holiday and no one is in the office. We will get back to you tomorrow.

Regards,

Nick Richards

0 Evan 2 months ago in reply to Nick Richards

TI__Genius 12215 points

Hi Craig,

Nick is correct in the forum.

Regards,

Evan

0 craig 2 months ago in reply to Evan

Intellectual 490 points

Is the accumulator supposed to downcount? The down count seems regular. Have you hooked up the device and read the register yourself?

0 Evan 2 months ago in reply to craig

TI__Genius 12215 points

Hi,

AccumulatedCapacity() should count up.

Regards,

Evan

Power management

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BQ35100EVM-795: 'Negative' Current on bqstudio?