Complete ADC function implementation with die temperature support
- Add comprehensive ADC reading functions (IBUS, IBAT, VBUS, VPMID, VBAT, VSYS, TS, TDIE)
- Implement proper 2's complement conversion for signed values (IBAT, TDIE)
- Add real-time ADC monitoring in test sketch (1-second intervals)
- Include die temperature measurement with 0.5°C resolution
- Hardware tested with BQ25628E showing correct register access and conversions
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
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