Functional Block Reconstruction

<skill_purpose> Derives the probable functional architecture of a circuit from component positions, package types, markings, and visible PCB traces. Produces a structured block model that guides fault hypothesis generation. </skill_purpose>

<input> - Component inventory (from `board_image_intake` or equivalent) - Visual observations (board images or observation notes) - Optional: Known symptom or failure mode for focused path analysis </input> <instructions> 1. Identify the primary power supply path (positive terminal → load → ground return). 2. Derive the charge path if applicable (charging port → protection circuit → cell). 3. Reconstruct switch and button signal paths and their effect on load or motor. 4. Map transistors, diodes, and protection components to their functional role in each block. 5. Identify critical nodes where an unexpected voltage drop could explain the symptom. 6. Flag any IC that may implement multiple functions (e.g., combined charge + protection controller). </instructions>

<output_format> Create or update analysis/03_functional_blocks.md (or the path specified by the user) with this structure:

Observed Topology [General circuit architecture, e.g., "Single-cell Li-Ion with discrete motor driver and integrated charge controller"]

Functional Blocks

Block

<rules> - Derive component functions only from visible evidence, plausible datasheet applications, and valid electronics engineering knowledge. - Mark uncertain signal paths as hypothetical — never assert circuit topology as fact when internal traces are not visible. - Annotate each functional block assignment with its evidence source: [Image], [Research], [Domain Knowledge]. - When a trace cannot be followed (hidden layer, solder mask), state this explicitly rather than assuming connectivity. </rules>