BQ34Z100-G1: spurious error readings of BQ34z100-G1

Hello Ernesto,

I think there was an issue with your image upload, you can use the insert file button to upload an image.

Are there any other devices on the I2C bus?

When you test with bqStudio try turning the scanning feature off (the green button in the top left of bqStudio) Sometimes when bqStudio tries to pull data for the log bqStudio is already doing a scan and causes interference.

Sincerely,

Wyatt Keller

image uploaded

Ernest

Hello Ernest,

Do you have any other devices on the bus that could interfere with communication?

Sincerely,

Wyatt Keller

Hi Wyatt,

there are not any other devices an I2C communication lines.

Pls note that when debugging with EV2300 tool I2C lines are connected directly from BQ34z10o to EV2300 I2C port.

I2C lines have 10K pull-up and signals on the scope have a normal shape.

Ernest

Hello Ernest,

How were you able to narrow down to the gauge? Does bqStudio also show spurious readings with the auto update off? If the values are only changing for one measurement it is most likely not the gauge setting to that value, because those values would then stay once changed.

Sincerely,

Wyatt Keller

Hello Wyatt,

in our design BQ34Z100 is placed in the main board rather than into the batter pack itself (user can not replace the battery pack). In our board we have a degug connector tied to I2C lines. MCU is connected to BQ34Z100 through two serial 0 ohms resistor, so by removing this resistors BQ is totally disconnected from our MCU and only connected to EV2300 I2C port.

Yes, BQStudio shows also spurious readings with auto update off. Pls see attached.

Yes, the gauge settings and values are ok, seems that the problem is just the communication for some of the samples.

I attach also a view of the BQ circutry.

Ernest

Hello Ernesto,

I would try testing with the EV2400, the EV2300 is a much older device. This is most likely a communication issue, make sure you leave space between subsequent readings, can you send a scope capture of the data?

Sincerely,

Wyatt Keller

Hi Wyatt,

we have arranged a test in which Watch was configured to read current each 5000 msec while capturing I2C signals on scope. Blue trace for data and yellow for clock. We have been able to capture a faulty reading.

Pls find attached a couple of captures. First one is a correct I2C read. Second one is an errored. Note that I2C data line keeps pulled at low level. In this situation I2C bus is only connected between BQ34Z100 and EV2300.

Which could be the cause of keeping data tied to "0".

Ernest.

Hello Ernest,

Is the final communication showing a NACK condition? I can't tell from the image.

What communication speed are you using?

Sincerely,

Wyatt Keller

Hi Wyatt,

normal communication is as:

S + ADDR(6..0) + "0" + A + CMD(7..0) + A + Sr + ADDR(6..0) + "1" + A + DATA(7..0) + A + DATA(7..0) + N + P

in erroneus communication we observe:

S + ADDR(6..0) + "0" + A + CMD(7..0) + A + Sr + ADDR(6..0) + "1" + A and after that we have just  a falling edge on the clock and a rising edge, while data keeps permanently at low level.

Pls see image in which you have a capture of last byte and last ACK

Communication frequency is 30 KHz which is the EV2300 own frequency.

Ernest

Hi Wyatt,

sorry for my late response. Our MCU uses I2C at 50 KHz aprox.

So, at this point the best solution for us is to include a filter in our MCU code to reject bad communication messages and in case of detecting an error generate a new query.

Thanks for your collaboration.

Ernest