Checksum calculation for bq27425

Ulrich Sorensen

Hi,

I have a problem getting the checksum to match according to the calculation method described in the data sheet. When I read 32 bytes (all default values) from data class 82 offset 0, I get a checksum value of 0x54 when reading register 0x60. When I sum the 32 byte values I have read, I get 0x566. Taking the LSByte I get 0x66 and then checksum should be 0xFF - 0x66 = 0x99. As you can see the to numbers does not match.

What am I doing wrong?

Best Regards,

Ulrich

over 12 years ago

0 Jared Casey over 12 years ago

TI__Expert 4115 points

Hello Ulrich,

When I calculate the checksum with the default values I get 0x54. My total is 0x7AB, then 0xFF - 0xAB = 0x54. When using EVSW the number of bytes that are read out needs to be a hex value, so the I2C command would be 0x40 and the Read Data Size would be 0x20. Can you provide the data values that you read out of that subclass?

0 Ulrich Sorensen over 12 years ago in reply to Jared Casey

Prodigy 30 points

Hi Jared,

I managed to get the checksum correct (I noticed I was missing some values in the calculation).

Thanks for your help.

Best Regards,

Ulrich

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Checksum calculation for bq27425