I am having mostly great success with the BQ27425 on my board. The things I can do successfully include:
- Read all of the RAM registers and get correct readings (e.g. battery voltage). I can also read the sub-command areas of the CONTROL command.
- Configure the block data interface so that I can read the block data (e.g. the gas gauge data).
So everything works pretty well, except I cannot write data to the NVM. Here's what I do:
- Write 0x00 to command 0x61 (enables block data access)
- Write 0x52 to register 0x3e (selects class 80, gas gauging)
- Write 0x00 to register 0x3f (selects data block 0)
- Read 32 bytes starting from register 0x40. These bytes match the default values shown for the gas gauge data in the datasheet.
- Read the checksum at register 0x60. This value matches the checksum I calculate from the bytes I read in the step above.
- I modify a single 8-bit value of the 32 8-bit values I previously read starting from register 0x40.
- I again write 0x00 to register 0x61, write 0x52 to register 0x3e, and 0x00 to register 0x3f again.
- I write all 32 bytes back starting at register 0x40. This seems to work properly.
- I write the new checksum I have calculated to register 0x60. This write succeeds, but the data does not get transferred to flash.
- I can change that final step (writing the checksum) so that it attempts to write an *invalid* checksum to 0x60. If I do this, the transaction fails on an I2C error returned by the BQ27425. This makes me pretty sure I have the correct checksum.
As a note:
- The VOK bit in the CONTROL_STATUS register is set.
- The SS bit in the CONTROL_STATUS register is clear.
Can you please let me know what the data may not be getting written to the NVM?
