BQ79652-Q1: Set All pins as Thermistor Input

Nisha Lemos

Part Number: BQ79652-Q1
Other Parts Discussed in Thread: BQSTUDIO

Hello

We are trying to use CFETOFF pin to sense the temperature. In order to do so we are using an external NTC with a 18kohm internal pullup resistor as raw value count.

Command Sequence is as follows:
W: 10 3e 90 00 - start config
W: 10 3e fa 92 3b - CFETOFF config
W: 10 60 38 05 - checksum
W: 10 3e 92 00 - End config
R: 10 6a 2 - without ground -data:- AC 4C
R: 10 6a 2 - when grounded -data:- 20 02

Could you help us in understanding the meaning of above values ?

We even want to set all pins with same configuration.

Regards

Nisha

over 1 year ago

0 Matt Sunna over 1 year ago

TI__Guru* 78383 points

Hi Nisha,

For most users, I would recommend using the 18K temperature model. This tool is very helpful for setting up the thermistor coefficient parameters: https://www.ti.com/tool/BQ769X2-THERMISTOR_COEFF_CALCULATOR

If you really want to use the raw ADC measurements (this can be pretty complex because you need to take into account the internal pullup resistor accuracy, etc.). This document outlines the different options:

4375.Thermistor_options_BQ76952.pdf

Best regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

The Calculator website seems to have some technical issue

Regards

Nisha

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

Can you describe the issues you are seeing with the tool? The link has changed slightly, so if you are using the link I sent in my last message, here is the updated link: https://www.ti.com/tool/BQ769X2-THERMISTOR-COEFF-CALCULATOR

Regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

I used the updated link provided by you, and followed the instructions and uploaded the zip file but, haven't received the Thermistor Coefficient Calculator report yet on the mail . We are using 10kohm 25ºC thermistor with beta value 3900 whose values are given in the below link on page no.16 and were provided in the zip file that I uploaded.

https://www.farnell.com/datasheets/33552.pdf

Can you please tell us the calculation steps for calculating the coefficients using these temperature and resistance values .

Also could you provide a checksum algorithm for BQ79652 written in C Language.

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

Maybe check your spam folder to see if the email did not go to your Inbox? I found your zip file that was submitted and loaded it to the online tool myself. There was one small mistake in your text file - there must be one blank line between the list of resistances and list of temperatures. See the report attached with the coefficients.

RequestorsZipFile-report.zip

Best regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

I will once test the Coefficient at my end and update you

Will it be possible to provide the algorithm to Calculate the Coefficient and Even the Checksum.

Regards

Nisha

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

Sorry, I cannot provide the algorithm to calculate the coefficients. This is a pretty complex program that searches for the optimum polynomial coefficients, but we cannot share details.

Which checksum are you referring to?

Regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna,

The checksum which is been used in BQ79652 to send sub-commands during configuration.

For Example:-

W: 10 3e 90 00 - start config
W: 10 3e fa 92 33 - CFETOFF config
W: 10 60 40 05 - checksum

Calculating the checksum for fa9233 as 40.

Regards,

Nisha

0 Nisha Lemos over 1 year ago in reply to Nisha Lemos

Prodigy 70 points

Hi Matt Sunna

I did the system configuration and set the coefficients to 18K model but still CFETOFF wasn't configured and same values were displayed as earlier i.e at the start. What should I do?

Below are the commands :

; bq769x2 Command Sequence File
; File Created on 2022-08-27 03:56:56 PM
R: 10 6a 16 -96 08 DB 09 02 00 B6 0B 94 08 B8 0B 91 08 92 08
W: 10 3e 90 00
W: 10 3e ea 91 F4 BE
W: 10 60 D2 06
W: 10 3e ec 91 52 71
W: 10 60 BF 06
W: 10 3e ee 91 F8 A9
W: 10 60 DF 06
W: 10 3e f0 91 D4 66
W: 10 60 44 06
W: 10 3e f2 91 3F 05
W: 10 60 38 06
W: 10 3e f4 91 45 F0
W: 10 60 45 06
W: 10 3e f6 91 4D 16
W: 10 60 15 06
W: 10 3e f8 91 72 EE
W: 10 60 16 06
W: 10 3e fa 91 EE 11
W: 10 60 75 06
W: 10 3e fe 91 B7 2D
W: 10 60 8C 06
W: 10 3e fa 92 0b
W: 10 60 68 05
W: 10 3e fb 92 0b
W: 10 60 67 05
W: 10 3e f7 92 0b
W: 10 60 6b 05
W: 10 3e fd 92 0b
W: 10 60 65 05
W: 10 3e fe 92 0b
W: 10 60 64 05
W: 10 3e ff 92 0b
W: 10 60 63 05
W: 10 3e 00 93 0b
W: 10 60 61 05
W: 10 3e 01 93 0b
W: 10 60 60 05
W: 10 3e 02 93 0b
W: 10 60 59 05
W: 10 3e 92 00
W: 10 3e ea 91
R: 10 40 22 -F4 BE 52 71 F8 A9 D4 66 3F 05 45 F0 4D 16 72 EE EE 11 00 00 B7 2D
R: 10 6a 16 -96 08 DB 09 02 00 B6 0B 94 08 B8 0B 91 08 92 08

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

This checksum looks correct (from your previous post).

Regarding loading your coefficients, have you first tried to input these in the BQStudio Data Memory screen? Then you can verify they are reading back correctly. If that works, you can export a .fs file from the Data Memory screen which is the same format as what you are showing.

Are you loading these values with a microcontroller?

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

Thank You Matt. It works, however regarding the checksum we are currently using an online checksum calculator but in order to do balancing of AFE in runtime we would have to upload a checksum algorithm in the controller itself. Could you provide the checksum algorithm?

Regards,

Nisha

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

If you download the Code Examples for the BQ769x2 (https://www.ti.com/product/BQ76952#software-development ), the checksum calculation is shown in this code.

Best regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

In reference with the command code I sent earlier , I tried to shorten the command code by making it in a single line as below :-

W: 10 3e 90 00
W: 10 3e ea 91 f4 be 52 71 f8 F9 d4 66 3f 05 45 f0 4d 16 72 ee ee 11 b7 2d
W: 10 60 c5 24
W: 10 3e fa 92 0b 0b 0b 0b 0b 0b 0b 0b 0b
W: 10 60 10 13
W: 10 3e 92 00

But this didn't configure the system. What can I do?

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

I think the problem is the length you are writing. This value should be in hex and it looks like you may be writing the decimal value.

Best regards,

Matt

0 Nisha Lemos over 1 year ago in reply to Matt Sunna

Prodigy 70 points

Hi Matt Sunna

I tried doing the configuration by doing the changes you suggested, all the coefficients except for a3 is getting configured . What could be the possible reason?

The desired value of a3 is -22024 and the value that is displayed is -22664.

0 Matt Sunna over 1 year ago in reply to Nisha Lemos

TI__Guru* 78383 points

Hi Nisha,

-22664 is the default value, so it seems like your write to this register was not successful.

I tried writing the data from you showed previously, but with the correct length and it works fine for me:

Best regards,

Matt

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BQ79652-Q1: Set All pins as Thermistor Input