BQ27421-G1: Schematic review & I2C read ISSUE

Hello Cho,

Make sure the correct pull up resistors are used for the communication lines, they are not populated in the schematic.

What communication issues are they having?

Sincerely,

Wyatt Keller

Pull Up is applied to the controller schematic.

They tried to read the data memory, but the 0xFF value was being read.

The Example 2: Reading the Firmware Version sequence of the sula467b document was applied.

slua467b.pdf

Additional

The customer says reading is normal on the Rev 0 board.

The other part of the two boards is whether the pull up resistance is added.

Rev 0 schematic : 

Hello Cho,

So the first revision is working, but when the pull-up resistors were added it stopped working in the next revision?

If this is being tested with an MCU you can compare the waveforms with bqStudio to see if you are sending the right sequence with your MCU.

Sincerely,

Wyatt Keller

Additional Verification Results, the MCU has also been changed.

The customer wants to review the controller part.

I'm sorry, but could you share the normal I2C waveform?

Hello Cho,

I can share what some commands look like, what are the commands you're trying to send? If you have the EV2400 and bqStudio you can check yourself as well by sending the same command with bqStudio and compare it to your MCU communication.

Sincerely,

Wyatt Keller

Thank you for your support.

Sorry, We don't have an EV2400 & EVM, so we can't check it ourselves.

I checked the customer's code and filled out additional questions and requests.

1. Normal waveform request : Reading the Firmware Version sequence

2. Question : Is there any problem with the schematic attached?

3. Question : The gauge IC is unlikely to operate normally under the conditions below. I think it's the cause of the I2C problem, Is that right?

- The customer is using only the read command without updating the Data Memory Parameter.

- It is operating in default state without updating the Data Memory Parameter.

Hello Cho,

To generate the original file golden file the EV2400 is usually used, how was the golden image generated?

I will provide more feedback tomorrow after checking the commands.

Sincerely,

Wyatt Keller

Hi Wyatt,

The customer did not generate a gold file.

I2C was applied with the default setting of BQ27421.

Isn't there anything to revise on the schematic?

Hi Wyatt,

I2C reading operation did not work, so we tested it by adding settings.

However, it does not operate from the version check.

Verify Existing Firmware Version

W: AA 00 01 00

C: AA 00 21 06

W: AA 00 02 00

C: AA 00 05 01

bq27621G1_201106_1.xls

What should we do to solve the I2C reading problem?

And is the normal waveform ready?

1. Normal waveform request : Reading the Firmware Version sequence

Hi Wyatt,

Thank you for your support.

We are planning to apply for EV2400 and test it.

I will end this question.

Hi Wyatt,

We connected the EV2400 and tested it.

I2C reading is normal with EV2400 connected.

I checked the waveform of I2C reads on the controller and I2C reads on EV2400.

The I2C waveform by the customer's controller is shown in the picture.

The waveform picture seems to show ACK twice.

I think this phenomenon is the cause of the problem.

Can you tell me why ACK number 2 appears?

Hi,

So gauge is communicating normally then?

Thanks,

Hi Nick,

There were no problems with I2C communications using the EV2400.

It does not work when I2C reads are performed using the customer's controller.

Hello Cho,

One of the time parameters is probably being violated for the gauge. Is the host holding the SDA line low or is it the gauge?

Sincerely,

Wyatt Keller