# Architecture diagram sources

The architecture Markdown embeds these 22 SVG figures. Matching PNG previews
are provided for viewers that do not support SVG. Diagrams describe the working
architecture; component qualification and schematic-release requirements remain
in the parent documents.

## Figures

| Topic | Figures |
| --- | --- |
| Power | [Sources](power-sources.svg), [protected branches](power-branches.svg) |
| Analogue acquisition | [Passive input](analog-input.svg), [thermistor](thermistor.svg), [ratiometric acquisition](ratiometric.svg) |
| Timing inputs | [Crank/cam interface](trigger-input.svg) |
| Deadman | [Contacts and diagnostics](deadman-inputs.svg), [permit gates](deadman-permit.svg), [output gates](deadman-outputs.svg) |
| Ignition | [Power](ignition-power.svg), [commands](ignition-command.svg), [current flag](ignition-flag.svg), [grounding](ignition-ground.svg) |
| Injection | [Power](injector-power.svg), [command](injector-command.svg), [status](injector-status.svg), [grounding](injector-ground.svg) |
| Generic outputs | [5 V logic](logic-output.svg), [low-side power](sink-power.svg), [supplies and SPI](sink-interfaces.svg), [command bias](sink-command.svg) |
| Optional DAC | [Output provision](dac-output.svg) |

## Editing and regeneration

- The 12 block figures have editable `.drawio` sources. Open them in draw.io.
  `build_blocks.py` recreates their baseline layout and `block-connections.json`.
  Running it overwrites manual layout edits, so update the generator when those
  edits should be reproducible, or export the edited `.drawio` directly.
- The 10 circuit/logic figures are generated by `build_circuits.py`, with a
  separate `*.topology.json` connection manifest for each figure. Change the
  relevant component/net definitions and layout together in that script;
  rerunning it overwrites the generated topology and images. JSON is a review
  manifest, not an independently interpreted rendering input.
- Reference designators introduced by these drawings are documentation labels,
  not KiCad assignments. Named continuation ports are electrically identical
  only when their names match within the documented domain.

Run from this directory using the configured schematic environment:

```bash
python build_blocks.py
~/.venvs/codex-schematics/bin/python export_blocks.py
~/.venvs/codex-schematics/bin/python build_circuits.py
```

`export_blocks.py` requires the installed draw.io desktop renderer; restricted
Electron sandboxes may require an authorized external execution. It exports
only `.drawio` inputs, keeps editable sources, checks for native SVG text, and
creates PNG previews. The circuit builder uses Schemdraw and CairoSVG.
Inspect changed figures at their intended embedded size after rebuilding.

Validate each circuit manifest with the installed topology validator:

```bash
~/.venvs/codex-schematics/bin/python \
  ~/.codex/skills/electronics-schematic-rendering/scripts/validate_topology.py \
  analog-input.topology.json
```

## Source clarifications in this redraw

- The former power-tree branch labelled `+5V_AUX` after 3.3 V filtering is now
  `+3V3_ANA`, matching the dedicated rail description. `+5V_AUX` remains a
  protected branch of `+5V_MAIN`.
- The passive ADC drawing now shows `C_HOLD` as a shunt capacitor after the
  small isolation resistor specified in the prose. It does not add a separate
  connector-side `R_PROT`. Exact values remain unspecified.
- The Hall-input drawing separates sensor supply, sensor return and signal;
  the original ASCII alignment could suggest an unintended join. The pull-up,
  divider and parallel filter follow the existing prose.
- The steering-wheel deadman switches are wired in parallel and present one
  shared `DEADMAN_IN` to the ECU. Either switch can assert permission. One
  `DEADMAN_STATUS` input reports the combined state; the ECU has no per-switch
  observations. The permission and output gates use the single `DEADMAN_OK`
  signal. See the module document for release and stuck-high fault behavior.
- `VBG_LOCAL_KELVIN` labels the documented local ignition reference at the
  `IGN_PGND` joining point. `LOCAL_GND` in the sink-command figure denotes the
  TLE9104SH local ground reference. Neither denotes a new remote ground path.
- The obsolete reference to a missing figure in `DIGITAL_INPUTS.md` was removed.
  That module remains described by its existing component-level prose.

Protection blocks whose devices or ratings remain unselected are deliberately
functional. Supply-loss behavior, real pin mappings, ratings and physical fault
responses still require the validation specified in the module documents.