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sistemas-cibernetico-fisicos/hardware/v2.9/README.md
Fábio Cunha 893778143a docs(sync): add README/AGENTS.md, fix hardware docs, sync central brain 
- Add root README.md and AGENTS.md for hardware repo

- Fix cross-repo and internal broken links

- Document hardware/common/scripts

- Populate v2.9 placeholder READMEs

- Update replica-omnisciente central brain pointer
2026-07-05 18:21:00 +01:00

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Savearth PCB v2.9 — Placeholder

This directory is a placeholder for the upcoming PCB v2.9 hardware revision.

Purpose

PCB v2.9 addresses the architectural flaws identified in v2.7 and v2.8:

Issue v2.7 v2.8 v2.9 Target
Reed switch pin GPIO43 (TX0) PCAL9538A P5 Dedicated RTC GPIO
Deep-sleep wake Yes (with UART conflict) No Yes via EXT1
Hard reset Cut regulator power None (always-on) Supervisor IC / delay circuit
Factory flashing Blocked by reed switch Tweezers on CON header On-board BOOT + RESET tactile buttons

Required Architectural Changes

  1. Reed Switch → RTC GPIO

    • Move the reed switch from the PCAL9538A I/O expander to a dedicated, non-strapping RTC GPIO on the ESP32-S3.
    • Candidate pins: GPIO4, GPIO5, or another RTC-capable pin that does not conflict with boot strapping (GPIO0, GPIO3, GPIO45, GPIO46).

  2. Hardware Hard-Reset Circuit

    • Long magnet hold (> 10 s) must unconditionally pull CHIP_PU (EN) LOW.
    • Options under evaluation:
      • Dedicated supervisor IC (e.g., LTC2950, MAX16054, TPS3420).
      • Passive RC delay + MOSFET / comparator.

  3. Soft-Latch Power Circuit (optional / TBD)

    • Replace the always-on EN-to-VSYS connection with a soft-latch that the firmware can release for true zero-power shutdown.
    • Requires a POWER_HOLD GPIO available immediately at boot.

  4. Tactile Buttons

    • Add RESET button: CHIP_PU → GND (100 nF debounce).
    • Add BOOT button: GPIO0 → GND (100 nF debounce).

Directory Layout

hardware/v2.9/
├── altium/                 # Altium Designer project placeholders
├── bom/                    # Bill of Materials placeholders
├── easyeda/                # EasyEDA Professional project placeholders
├── manufacturing/          # Gerber, pick-and-place, 3D STEP placeholders
└── parsed_data/            # Extracted schematic/BOM/netlist placeholders

Open Decisions

  • RTC GPIO selection for reed switch.
  • Supervisor IC vs. passive RC for hard reset.
  • POWER_HOLD GPIO selection (if soft-latch is implemented).
  • Boot/reset button footprint and enclosure cutout strategy.
  • BOM cost target and budget for added components.
  • PIR noise: hardware RC filter required or firmware-only debounce?

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