PEC crc calculation

David Rzepka

I'm having a problem matching my crc calculation to the one I'm getting back from your chip. I'm able to set the PEC bit in Cfg B using the eval software and now I'm receiving the crc, but it doesn't match the calculation in my software. As an example, I send a simple 0x01 RemainingCapacityAlarm command and I receive 0xCC 0x01 0xCD, where 0xCD is your crc. My calculation of the crc is 0x16. Am I missing something here??? Are more bytes being used for your crc than just the 2 data bytes??? Is there some special crc seed being used, like doing an xor with 0xFF on the first byte??? Thanks

over 14 years ago

0 Chase7071949597 over 14 years ago

TI__Genius 10235 points

The PEC calculation includes everything in the packet. For a Read Word, the following is included in the checksum:

0x16

Command Code

0x17

Data LSB

Data MSB

For example, if your command code is 0x0D (Relative State of Charge) and your data is 0x0010, then the value you will compute the checksum on is 0x160D171000. This would result in a checksum of 0x64.

You can use the calculator at the following link to check your results. This calculator uses the same method that is in the gauge.

http://smbus.org/faq/crc8Applet.htm

0 David Rzepka over 14 years ago in reply to Chase7071949597

Prodigy 50 points

0 David Rzepka over 14 years ago in reply to David Rzepka

Prodigy 50 points

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PEC crc calculation