BQ20z65 writing directly to subclass 104 with writeSMBusblock

Deckerg

Other Parts Discussed in Thread: BQ20Z65I'm trying to programatically calibrate the current in a BQ20z65. Using the code example from SLUA379E doesn't work because it seems to require current flowing across the sense resistor independent of the FETs, and I don't have access to test points that would let me do that. I'm trying to use the method described in section 5.1 where I program CC gain and CC delta directly, but it's not working. I can read the calibration register (subclass 104) but the numbers don't make any sense and I cannot figure out how to convert the hex byte array into the floating point decimal that shows up in the Data Flash page of the BQ software. For CC gain and CC delta of 3.0 each, for example, I get 0x82 0x48 0xF0 0x4C 0x94 0x64 0x9F 0xA0. The 0x82 and 0x94 don't change not matter what I program the value to, so that means that 0x48 0xF0 0x4C and 0x64 0x9F 0xA0 both equal 3.0. How does this conversion work?

over 10 years ago

0 Mike Ewer over 10 years ago

TI__Intellectual 2650 points

Please refer to appendix A of this document for the conversion process

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slva148&fileType=pdf

0 Deckerg over 10 years ago in reply to Mike Ewer

Intellectual 685 points

That does not work. The results of the 8 Byte read when CC Delta and CC Gain are both 2.982 gives me 82 4A 26 CD 94 66 00 E9. Presumable 82 4A 26 CD is CC Gain and 94 66 00 E9 is CC Delta. This already makes no sense, as CC Gain and CC Delta both equal 2.982 in my GG file. The results of the conversion in the code example you linked above gives me 83 5F 6C 8B when I enter 2.982 for X. That doesn't match either register read for CC Delta or CC Gain. What am I doing wrong?

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BQ20z65 writing directly to subclass 104 with writeSMBusblock