BQ76PL455A-Q1: Cannot read aux temperature correctly

Hi Jun,

Are they using BQ76PL455A EVM or their our design? If using their own design, please share the schematic and picture of their setup to make sure everything is ok with the hardware.

Do they see the same problem when using the device GUI?

What line of the code is where they are seeing the issue?

Best regards,
Leslie

Hi Leslie-san,

I confirm with the customer and then will get back to you.

Regards,

Jun

Hi Leslie-san,

The issue is occurring their own board, not EVM. They think the issue is removed by dummy-read so the cause seems to be due to their software. The length between MCU and bq76pl455a-q1 is less than 50cm in the environment of almost no noise. They don't use TI's GUI for this testing.

The code they are seeing the issue is at 277-line in sys_main.c. Please provide any comments for above (1)~(4) from the software/register setting point of veiw?

Regards,
Jun

Hi Leslie-san,

Could you provide any feedback to us?

Regards,
Jun

Hi Jun,

My apologies for the delay. I will look into this in my morning (Dallas, TX time) and get back to you.

Regards,
Leslie

Hi Jun,

Please share the "BQ76PL455Q-A1 Software design reference" document with the customer (www.ti.com/.../slva617a.pdf). Section 2 has step by step details of how to configure the AFE, and Section 4 has step by step details on how to read the ADC voltages. This explains the code written in the example code.

Please see my response to your questions below:

(1) Currently the customer can read the correct value for AUX temperature by using dummy read at first time. Do you think that is suitable workaround for this issue?

Answer LMA >> They shouldn't need a dummy read. If they are running the example code as is without any modifications that might be the issue. The example code is written in a way to provide example code for several scenarios (e.g. if there is a stack of 3 devices, if there is a single device, if you want the device to sample and store ADC readings but not return them, if you want the device to capture and return back ADC readings, etc.). Therefore, they should only leave the piece of code needed for their specific scenario.

(2) Please let us know the necessary processes after "select cell channels 1-8" and "AUX channels" in the initialization of the device?

Answer LMA >> The steps to configure the ADC can be found in the
o be able to recommend the right settings for their application, can you please provide the following information:
* How many BQ76PL455A-Q1 devices they have connected in the stack
* How many cells they are using in their application
* Which AUX channels they are trying to sample? (example code samples the first 2 AUX channels)

(3) Does this device need some wait time to read voltage and AUX temp values after the initialization of the device?

Answer LMA >> There is a delay that can be configured from the time a sample command is received to when the device actually samples, but it is set to 0 in the example code. There is also a sampling period setting per channel that is set to 100us in the example code

(4) Do you have any other workarounds to remove this issue?

Answer LMA >> A workaround shouldn't be needed. Once we know the details on what they are trying to configure (how many channels, AUX channels and stacked devices) it should work

SIDE NOTE:
Please make sure that the number of devices they have connected in the stack, matches the number of devices defined in "pl455.h" file in the "include" folder. In "pl455.h" file, line 30, the total number of boards is defined. In the example code is set to 16, but if you are using only 1 board, please change this line from "TOTALBOARDS 16" to "TOTALBOARDS 1"