BQ40Z50-R2: SMBus Communication Error

Zhihan Zhang

Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Hi TI Team,

I currently have some communication issue between host and 40z50 device. More specifically, I found that in some cases, 40z50 device may NACK the commend from the host. And once NACK happens, the next 2 same commends will be NACK as well. Then host will set alarm.

For example, host needs to read temperature. When it send 0x08, the device may NACK it. Then host will repeat sending 0x08 for another 2 times and the device may continue NACK those.

So can you please advise what may be the cause?

Additionally, once device NACK the commend, is there any "rest time" required for the device? For example, if the device NACK the 1st 0x08 commend, does host need to wait for certain period then send 2nd 0x08 commend to avoid continuous NACK from the device?

Thanks,

Zhihan

over 4 years ago

0 Wyatt Keller over 4 years ago

TI__Guru** 105760 points

Hello Zhihan,

Can you share any scope captures of this occurring? Does it happen with the EV2400 and bqStudio or just your host MCU?

Sincerely,

Wyatt Keller

0 Zhihan Zhang over 4 years ago in reply to Wyatt Keller

Expert 1100 points

Hi Wyatt Keller,

It happens with host MCU. EV2300 and bqStudio are ok.

Also attached the waveform. Please kindly review.

Thanks,

Zhihan

0 Wyatt Keller over 4 years ago in reply to Zhihan Zhang

TI__Guru** 105760 points

Hello Zhihan,

What frequency are you communicating at?

The best way to debug is compare the scope/logic analyzer captures with bqStudio, if you are using 400kHz make sure the XL mode is set.

Sincerely,

Wyatt Keller

0 Zhihan Zhang over 4 years ago in reply to Wyatt Keller

Expert 1100 points

Hi Wyatt Keller,

We first used ~95kHz, then we cut half to ~50kHz. But still we met the same problem.

Also, our customer is curious if there is any restart time after 40z50 NACK the commend? Or what action 40z50 will take after it NACK the commend? Please kindly advise!

Thanks,

Zhihan

0 Wyatt Keller over 4 years ago in reply to Zhihan Zhang

TI__Guru** 105760 points

Hello Zhihan,

If bqStudio is working correctly and the NACK is only occurring with the host MCU, there may be something wrong with the driver being used.

I attached an example reading firmware using logic analyzer (and I2C based gauge).

Sincerely,

Wyatt Keller

0 Zhihan Zhang over 4 years ago in reply to Wyatt Keller

Expert 1100 points

Hi Wyatt Keller,

Thanks! Will ask customer to try on logic analyzer and comparing with bqstudio waveform.

And what about the reset or restart time of 40z50 after NACK? Or what is the next move of IC when it NACK host commend?

Thanks,

Zhihan

0 Wyatt Keller over 4 years ago in reply to Zhihan Zhang

TI__Guru** 105760 points

Hello Zhihan,

The host is most likely violating one of the timing requirements from the gauge data sheet.

Sincerely,

Wyatt Keller

0 Zhihan Zhang over 4 years ago in reply to Wyatt Keller

Expert 1100 points

Hi Wyatt Keller,

When our host side engineer working on the issue, they found that the NACK is more likely to take place during battery is discharging. Can you please kindly advise if this is expected and what may be the casue?

Thanks,

Zhihan

0 Wyatt Keller over 4 years ago in reply to Zhihan Zhang

TI__Guru** 105760 points

Hello Zhihan,

The state of the gauge should not make a difference for the NACK. Have you checked other threads on E2E regarding this issue?

e2e.ti.com/.../493602

Sincerely,

Wyatt Keller

Power management

Power management forum

BQ40Z50-R2: SMBus Communication Error