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mattandClaude ad9c457ea7 Initial firmware for ESP32-S3 six-channel soil moisture node 
Implements ESP32_Soil_Moisture_Node_PRD.md on the VCC-GND Studio
YD-ESP32-S3 (ESP32-S3-WROOM-1) using Arduino via PlatformIO, publishing
to Home Assistant over MQTT with auto-discovery.

Two power profiles behind a compile-time switch (PRD 4):
  -e mains    always on, publishes every 60s
  -e battery  RTC wake, sample, publish, deep sleep 15min

PRD mitigations:
  - All six probes on ADC1 (GPIO4-9); ADC2 is unusable while Wi-Fi is up.
  - analogReadMilliVolts() for eFuse ADC calibration rather than raw counts.
  - 16 samples per probe, sorted, 10% trimmed from each end, averaged.
  - Per-probe two-point calibration; HW-390 output is inverted (dry reads
    high), and an inverted config is rejected rather than silently producing
    a backwards curve.
  - MAC-derived node ID so identical binaries never collide on topics.

Design decisions that diverge from a literal reading of the PRD:
  - Out-of-range probes publish null (HA "unknown") instead of clamping to
    0%/100%. A cut Cat5 pair reads ~0mV, which clamps to a believable "very
    dry" and would drive irrigation on wrong data.
  - The battery profile uses expire_after rather than an availability topic;
    a sleeping node is offline most of the time and would sit greyed out.
  - AWAKE_BUDGET_MS forces deep sleep if a wake cycle overruns, covering
    failure modes the per-step network timeouts miss (DHCP never issued,
    CONNACK never sent) that would otherwise flatten the cell.
  - docs/WIRING.md notes the 18650 cannot feed the probes directly: the
    XC6206 LDO needs ~3.4V headroom, so a boost converter is required on the
    switched side of the MOSFET.

Both profiles compile clean under -Wall. Not yet run on hardware; pin map,
MOSFET circuit and calibration defaults are unverified against a board.

Co-Authored-By: Claude <noreply@anthropic.com>
2026-08-14 13:38:41 -07:00

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<title id="t4">Solar and battery power topology with boost converter and battery sense divider</title>
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<text class="ttl" x="20" y="30">Solar / battery topology — remote node</text>
<text class="s" x="20" y="49">The cell cannot feed the probes directly: an 18650 runs 3.0–4.2V and the HW-390's XC6206 LDO needs ~3.4V of headroom.</text>
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<rect class="boxp" x="24" y="96" width="150" height="80" rx="6"/>
<text class="h" x="38" y="120">Solar panel</text>
<text class="m" x="38" y="139">6V / 1–2W</text>
<text class="s" x="38" y="158">sized for winter, not</text>
<text class="s" x="38" y="171">for a sunny afternoon</text>
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<text class="h" x="236" y="120">TP4056 + DW01</text>
<text class="m" x="236" y="139">CC/CV charger</text>
<text class="s" x="236" y="158">protection variant only</text>
<text class="s" x="236" y="171">— no MPPT</text>
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<rect class="boxp" x="430" y="96" width="140" height="80" rx="6"/>
<text class="h" x="444" y="120">18650 Li-Ion</text>
<text class="m" x="444" y="139">3.0 – 4.2 V</text>
<text class="s" x="444" y="158">VBAT node</text>
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<text class="h" x="736" y="79">ESP32-S3 · 5V/VIN</text>
<text class="s" x="736" y="97">onboard reg accepts VBAT</text>
<text class="m" x="736" y="112">deep sleep ≈ 10 µA</text>
<rect class="boxp" x="722" y="176" width="192" height="62" rx="6"/>
<text class="h" x="736" y="199">Boost converter → 5V</text>
<text class="s" x="736" y="217">on the SWITCHED side of</text>
<text class="s" x="736" y="231">the P-FET, not before it</text>
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<text class="h" x="736" y="310">P-FET → Cat5 pin 2</text>
<text class="s" x="736" y="329">see power-switch.svg</text>
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<text class="m" x="528" y="252">R1 1 MΩ</text>
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<text class="h" x="34" y="431">Why 1 MΩ and not the usual 100 kΩ.</text>
<text class="s" x="34" y="450">A 100 kΩ/100 kΩ divider draws ~21 µA continuously — more than the sleeping MCU itself (~10 µA), and enough to dominate</text>
<text class="s" x="34" y="468">the winter power budget. 1 MΩ/1 MΩ draws ~2 µA. The 1 µF cap is not optional at that impedance: it supplies the ADC's sampling charge.</text>
<text class="s" x="34" y="486">Trim BATTERY_DIVIDER_RATIO in config.h against a meter to cancel resistor tolerance.</text>
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