BQ76PL455A-Q1: Power management forum

AKSHAA TP

Part Number: BQ76PL455A-Q1

Hi,

We are working on a BMS design using two bq76pl455a-q1 ICs with stm32f207 microcontroller as master.

We could get the addressing and configuration done for the battery monitor IC but reading and sampling voltage values gives us a wrong response even if we try with different sampling rates or change the 16 bit addressing commands to 8 bit ones. We tried two approaches --> sampling, storing and returning the results as well as the other approach of sampling and storing as given in the software technical manual (PFA below). Correct voltage values are received for some but some channels were constantly on a default value of 5V which was verified with the logic analyzer as well.

The commands passed for reading channel data are given below:

//read data from all 16 cell channels, 8 aux channels and sum of voltages

data[0] = 0x89; //read all channels- 16cells, 8aux, sum of volt
data[1] = 0x00;
data[2] = 0x00;
data[3] = 0x02;
data[4] = 0x00;

(data[5] data[6] are the higher and lower bits of the CRC)

Kindly tell us if we are accessing the channels in a wrong way or if there is a particular sample rate or a UART baud rate to be used.

Documents referred:

bq76PL455A-Q1 SOFTWARE TECH MANUAL: https://www.ti.com/lit/an/slva617a/slva617a.pdf?ts=1615918882996

bq76PL455A-Q1 datasheet

Thanks.

over 4 years ago

0 Taylor Vogt over 4 years ago

TI__Genius 17370 points

Hi Akshaa,

Can you share the exact hex commands you are sending via a logic analyzer on the RX/TX lines? Did you follow all of the AFE configuration commands from the software manual? Did you measure the channels with a digital multimeter to compare against the AFE output of the device?

Regards,

Taylor

0 AKSHAA TP over 4 years ago in reply to Taylor Vogt

Prodigy 40 points

Hi Taylor,

Keeping other configurations as default, NCHANNEL was selected for 16 channels -99 00 00 0d 10 & crc.
Channel select was written to choose all cell, aux 0 and 1, digital and analog die temperature as per the reference manual - 9C 00 00 03 ff FF 03 C0.
The values received are erroneous.

Yes, all AFE config commands were followed and the channel voltages were measured. In fact, the voltage values are being read correctly on the bq-eval software. Also I want to add that we tried different commands given in reference manual like the '20' of read sampled values.

Thanks!

0 Taylor Vogt over 4 years ago in reply to AKSHAA TP

TI__Genius 17370 points

Hi Akshaa,

I don't think I understand your commands - the second digit determines how many bytes to write after the 9 to be a single device write. So it doesn't seem like you are writing enough bytes correctly. Try writing one byte at a time using 91 as the first byte like the reference manual does.

Regards,

Taylor