SLUAAF8 October   2021 BQ24707 , BQ24707A , BQ24725A , BQ24735 , BQ24770 , BQ24780S , BQ24800 , BQ25700A , BQ25708 , BQ25710 , BQ25720 , BQ25730 , BQ28Z610-R1 , BQ4050 , BQ40Z50 , BQ40Z50-R1 , BQ40Z50-R2 , BQ40Z80

 

  1.   Trademarks
  2. 1Introduction
  3. 2Smart Battery Setup
    1. 2.1 Gauge Setup
      1. 2.1.1 I2C System Differences
    2. 2.2 Charger Setup
  4. 3Communication Protocol
  5. 4Data Collected
  6. 5Summary
  7.   A Appendix
    1.     A.1 General Setup
    2.     A.2 Gauge Setup - SMBus
    3.     A.3 Gauge Setup - I2C
    4.     A.4 Charger Setup
    5.     A.5 Charge Voltage Example
    6.     A.6 Charge Current Example
  8.   B References

A.5 Charge Voltage Example

An example of the charging voltage communication with the packet structure follows:

0x12 (write) 0x15 0xD0 0x20 0x73

Charging voltage is transmitted in little endian as well, so the bytes must be swapped:

Voltage: 0x20D0 = 0010 0000 1101 0000

Comparing the register bit definitions, the charge voltage can be calculated:

8192 + 128 + 64 + 16 = 8400 mV

GUID-20210730-SS0I-DWWL-4VJ2-186SDDHFPPZT-low.pngFigure 6-5 Voltage Write From Gauge to the Charger in Broadcast Mode

A CRC-8 calculator can be used for verifying the PEC byte of the voltage and current examples, the PEC byte can be calculated using the data sent previously as a type of checksum(9). To check the PEC byte, use the bytes 0x12, 0x15, 0xD0, and 0x20 as the CRC calculator input. The calculated byte should be the PEC byte.