BQ76952: BQ76952 interfacing with NXP's S32K144 MCU

Hello Hareesh,

Do you mind sharing if there were any errors the code gave back? Also, when you are saying unable to read the cell voltages from the AFE, can you still communicate with the AFE at all?

Best Regards,
Alexis

Hi Alexis,

Thanks for the reply.

Alexis_H said:

Do you mind sharing if there were any errors the code gave back?

No, we are not getting any errors.

Alexis_H said:

Also, when you are saying unable to read the cell voltages from the AFE, can you still communicate with the AFE at all?

No, we are not able to communicate with the AFE.

Best regards,

Hareesh

Hello Hareesh,

Do you mind sharing a schematic of your connections?

When you said you connected REG1 to 3.3V, are you supplying 3.3V to REG1?

Also, do the SDA and SCL lines have pullups to REG1 or 3.3V?

Best Regards,
Alexis

Hi Alexis,

Alexis_H said:

Do you mind sharing a schematic of your connections?

We connected the circuit as shown in below, which we got from the BQ76952 data sheet.

Alexis_H said:

When you said you connected REG1 to 3.3V, are you supplying 3.3V to REG1?

Yes, we are giving 3.3V to REG1 from the MCU.

Alexis_H said:

Also, do the SDA and SCL lines have pullups to REG1 or 3.3V?

The pullups (10kohm each) are already linked to 5.0V from the MCU side.

Best regards,

Hareesh

Hello Hareesh,

Hareesh Gorle said:

Yes, we are giving 3.3V to REG1 from the MCU.

Thanks for clarifying. REG1 is an LDO that can output voltages at various levels, so you would not need to supply 3.3V from the MCU to it. 

Hareesh Gorle said:

The pullups (10kohm each) are already linked to 5.0V from the MCU side.

Thanks for confirming this. Could you share any logic analyzer files of the SCL/SDA lines when you try to communicate? What commands/subcommands are you sending? Also, what is the voltage of REG18 and RST_SHUT as you try to communicate with the part as well?

Best Regards,
Alexis

Hi Alexis,

Alexis_H said:

what is the voltage of REG18 and RST_SHUT as you try to communicate with the part as well?

The voltages at pin:

REG18 - 3.8V

RST_SHUT - 0V

REG1 - 3.3V

Alexis_H said:

Could you share any logic analyzer files of the SCL/SDA lines when you try to communicate?

Kindly find the attached file for SCL and SDA signal captures.

SCL_SDA_signals.rar

Alexis_H said:

What commands/subcommands are you sending?

Please find the following code:

	CommandSubcommands(BQ769x2_RESET);  // Resets the BQ769x2 registers
	Delayus(60000);
	BQ769x2_Init();  // Configure all of the BQ769x2 register settings
	Delayus(10000);
	CommandSubcommands(FET_ENABLE); // Enable the CHG and DSG FETs
	Delayus(10000);
	CommandSubcommands(SLEEP_DISABLE); // Sleep mode is enabled by default. For this example, Sleep is disabled to demonstrate full-speed measurements in Normal mode.

Best regards,

Hareesh

Hello Hareesh,

REG18’s voltage is above the abs max of 2V. This can potentially occur when there is a GPIO that is connected to a higher voltage and is configured to be connected internally to REG18.

Do you mind sharing your schematic? If you would like it to be private, you can DM it to me.

Also, somethings to note:
1. Does your MCU support clock stretching? If the MCU does not support clock stretching, the device will not be able to properly communicate.
2. What is the I2C device address of the BQ769x2 family?

Best Regards,
Alexis

Hi Alexis,

Alexis_H said:

Do you mind sharing your schematic?

We are referring the following reference design which was mentioned in the BQ65952 data sheet.

We connected the following pins between the MCU and the BQ7695202 AFE based on the reference design:

DFETOFF

RST_SHUT

ALERT

SDA

SCL

GND.

Please advise whether there are any pins I should connect in order to read the AFE's cell voltages.

Alexis_H said:

1. Does your MCU support clock stretching?

Yes, the MCU will support the clock stretching.

Alexis_H said:

2. What is the I2C device address of the BQ769x2 family?

We are giving the I2C device address as 0x10.

Best regards,

Hareesh

Hello Hareesh,

Were you able to communicate before any configuration changes were made or did communication stop after configuration changes were made?

Are you driving voltages to the DFETOFF/ALERT pins or any other pins of the AFE?

There shouldn’t be any other pins that need to be connected to read the AFE’s cell voltages if SCL/SDA are connected properly to communicate with the device and the cells are attached. 

Since you can’t communicate with the device, you aren’t going to be able to read the cell voltages. I’m trying to determine where/when this communication issue occurred.

REG18 shouldn’t be reading 3.8V, so it would be good to determine how it’s going so high.

Best Regards,
Alexis