Description

HeatControl is a dual-zone heating control system for drysuit diving, based on ESP32-C3. The controller regulates two heating channels using DS18B20 sensors and SSR/MOSFET outputs, monitors MOSFET temperature with two NTC sensors, and provides a web UI for setup and live monitoring.

Features

• Dual-zone temperature control
• Web interface with live status
• Adjustable targets (10-45 C)
• Persistent settings in EEPROM
• Three modes:
  • Normal: temperature-based control (requires two valid sensors)
  • Power: full power output
  • Manual: fallback PWM mode when fewer than two sensors are available
• Swappable sensor assignment
• Captive portal AP mode
• OTA firmware upload from web UI (/update)
• MOSFET overtemperature protection with 2x NTC (trip at 80 C, re-enable at 75 C)

Hardware

Requirements

• ESP32-C3 board (DevKitM-1 compatible)
• 2x DS18B20 temperature sensors
• 2x SSR/MOSFET channels for heating
• 2x NTC thermistors (10k, B3950 recommended) for MOSFET monitoring
• 2x 10kOhm resistors (for NTC voltage divider)
• Step-down converter (15V to 5V)
• 1000uF capacitor
• 4.7kOhm pull-up for OneWire

Pin Mapping (current firmware)

• GPIO7 -> OneWire bus (ONE_WIRE_BUS)
• GPIO2 -> Heater channel 1 (SSR_PIN_1)
• GPIO5 -> Heater channel 2 (SSR_PIN_2)
• GPIO10 -> Boot mode input (INPUT_PIN)
• GPIO6 -> Startup signal output (SIGNAL_PIN)
• GPIO0 -> ADC voltage input 1 (ADC_PIN_1)
• GPIO1 -> ADC voltage input 2 (ADC_PIN_2)
• GPIO3 -> MOSFET 1 NTC ADC input (ADC_PIN_NTC_MOSFET_1)
• GPIO4 -> MOSFET 2 NTC ADC input (ADC_PIN_NTC_MOSFET_2)
• GPIO8 -> Battery 1 presence LED (BATTERY_LED_PIN_1)
• GPIO9 -> Battery 2 presence LED (BATTERY_LED_PIN_2)
• GPIO20/GPIO21 -> UART0 reserved (left free by firmware)
• GPIO18/GPIO19 -> Native USB reserved (left free by firmware)
• GPIO2/GPIO8/GPIO9 -> Strapping pins; do not use for fixed voltage-divider inputs

NTC Wiring (per MOSFET channel)

• Divider topology used by firmware: 3.3V -> NTC (10k, B3950) -> ADC node -> 10k resistor -> GND
• Channel 1 ADC node -> GPIO3 (ADC_PIN_NTC_MOSFET_1)
• Channel 2 ADC node -> GPIO4 (ADC_PIN_NTC_MOSFET_2)
• Important: keep ADC pin voltage within 0..3.3V
• Important: avoid GPIO2/GPIO8/GPIO9 for NTC or battery divider inputs (ESP32-C3 strapping pins)

Interface

Pinout

Show rotated pinout (+90°)

Show rotated pinout (+180°)

Show rotated pinout (+270°)

Important note about pin names (GPIO vs D-labels):

• The firmware uses GPIO numbers (e.g. GPIO4) in src/app_state.h.
• Some ESP32-C3 boards also print D-labels (e.g. D2) on the silkscreen/pinout image. These are just aliases.
• When wiring, you can use either label, but always match the GPIO number.

Connections (see src/app_state.h):

GPIO	Board label	Function	Connect to
7	D5 / SS	OneWire bus	DS18B20 data line (with 4.7kΩ pull-up to 3.3V)
2	A2	Heater channel 1	SSR/MOSFET control (SSR_PIN_1)
5	D3 / A3	Heater channel 2	SSR/MOSFET control (SSR_PIN_2)
6	D4 / SDA	Startup signal output	Optional status LED or external signal (SIGNAL_PIN)
10	D10 / MOSI	Boot mode input	Optional: hold low/high for power vs normal mode (INPUT_PIN)
0	ADC1-0 / A0	ADC voltage input 1	Voltage sense input (use a divider; max 3.3V at the pin)
1	ADC1-1	ADC voltage input 2	Voltage sense input (use a divider; max 3.3V at the pin)
3	D1 / A1	MOSFET 1 NTC ADC input	NTC divider on MOSFET 1 (ADC_PIN_NTC_MOSFET_1, max 3.3V at pin)
4	D2 / A2	MOSFET 2 NTC ADC input	NTC divider on MOSFET 2 (ADC_PIN_NTC_MOSFET_2, max 3.3V at pin)
8	(GPIO8)	Battery 1 LED	Battery 1 presence/status LED (BATTERY_LED_PIN_1, active HIGH)
9	(GPIO9)	Battery 2 LED	Battery 2 presence/status LED (BATTERY_LED_PIN_2, active HIGH)
20/21	RX/TX	UART0	Reserved/free for serial adapter or debugging
18/19	USB D-/D+	Native USB	Reserved/free for optional native USB

Note: INPUT_PIN here is a project-specific boot-mode input on GPIO10 / D10 (not the ESP32-C3 BOOT button/strapping pin). Note: GPIO2, GPIO8, and GPIO9 are ESP32-C3 strapping pins. Keep fixed dividers (NTC/battery) off these pins to avoid boot issues. Note: ADC readings are reported in the UI/Serial as millivolts (analogReadMilliVolts). Note: MOSFET overtemperature protection uses both NTC channels and blocks the affected heater above 80C (re-enable below 75C). The trip is persisted as a latched diagnostics event (incl. trip temperature), shown as HOT/TRIP in the heater cards, and can be acknowledged via the Diagnostics reset button.

Vibration / signal patterns (SIGNAL_PIN / GPIO6)

SIGNAL_PIN (GPIO6) can drive a small vibration motor or an LED to provide haptic/visual feedback.
The firmware uses the following patterns (timings are approximate):

• Boot: normal mode

  • Pattern: 1× long pulse (HIGH ~300 ms, LOW ~200 ms)
  • When: Device starts in normal temperature-control mode.

• Boot: power mode

  • Pattern: 2× long pulses (each HIGH ~300 ms, LOW ~200 ms)
  • When: Device starts in power mode (full power).

• Boot: manual mode

  • Pattern:
    • 1× long intro pulse (HIGH ~500 ms, LOW ~220 ms)
    • Then N short pulses to show the manual power for heater channel 1:
      • 1× short pulse → 25 %
      • 2× short pulses → 50 %
      • 3× short pulses → 75 %
      • 4× short pulses → 100 %
    • Short pulses are HIGH ~130 ms, LOW ~130 ms.
  • When: Fewer than two DS18B20 sensors are detected and the controller enters manual mode at boot.

• Manual mode: change of manual power (heater 1 or 2)

  • Pattern:
    • N short pulses (HIGH ~130 ms, LOW ~130 ms) encoding the new manual duty:
      • 1× short pulse → 25 %
      • 2× short pulses → 50 %
      • 3× short pulses → 75 %
      • 4× short pulses → 100 %
  • When:
    • A short battery OFF/ON sequence (voltage drop < threshold, power returns within a configurable window, default ~500 ms) toggles the manual power step for the corresponding heater channel. Longer OFF periods do not change the step. The window can be adjusted in the web UI (Diagnostics → OFF/ON detection window).
    • The manual power for both channels is cycled once at boot when in manual mode and INPUT_PIN is held HIGH (first selection feedback).

• Web API test pulse

  • Pattern: 1× very short pulse (HIGH ~120 ms)
  • When: HTTP POST to /signalTest (useful to verify wiring of LED/vibration motor).

Network: AP IP 4.3.2.1 · Default SSID HeatControl · OTA at /update

Web Interface

Screenshots:

• Heaters (main controls):

• WiFi settings (STA/AP + timeout):

• OTA section entry (buttons inside Advanced):

• Diagnostics/system actions (battery, runtime, etc.):

• OTA upload page (/update):

• Serial log panel:

• MOSFET overtemp indicator (HOT/TRIP badge):

The web interface provides:

• Live temperature readings
• Target temperature controls
• Heater status indicators
• Sensor swap option
• MOSFET NTC diagnostics (mV + C) and HOT/TRIP warnings per heater card
• WiFi configuration
• Runtime reset
• MOSFET overtemp-history reset (acknowledge latched events)
• OTA update upload page

Notes:

• "Advanced" contains WiFi, OTA, diagnostics and system actions.
• The mode is reported by the device (AUTO/POWER/MANUAL) and is not a manual toggle.

Installation

1. Clone this repository
2. Open it in PlatformIO
3. Build and upload to ESP32-C3
4. Connect to AP HeatControl
   • SSID: HeatControl
   • Password: HeatControl

Operation

1. Power on the device
2. Connect to the AP
3. Open http://4.3.2.1
   • If desktop captive portal does not open automatically, open http://4.3.2.1 directly.
4. Configure targets and monitor status
5. Optional OTA update: open /update and upload firmware.bin

Tests

• Native logic/unit-tests: export PATH=$PATH:~/.local/bin && pio test -e native

Hardware-free web UI testing

You can test the web UI in a browser without an ESP by serving the static files from upload/ together with a small mock API.

• Start the mock server (local only): python3 tools/dev_web_mock.py --host 127.0.0.1 --port 8080
• Open the UI: http://127.0.0.1:8080/
• Helpful endpoints: http://127.0.0.1:8080/status and http://127.0.0.1:8080/logs

The mock server also provides test-only endpoints for switching states without modifying the real UI:

• Read current mock state: GET /__mock/state
• Update mock state: POST /__mock/state (JSON or form data)
• Reset mock state: POST /__mock/reset

If you need access from another machine in your LAN, use --host 0.0.0.0 and make sure the port is reachable.

Selenium smoke test

If you have Google Chrome/Chromium available, you can run a minimal UI smoke test via Selenium.

• Install: pip install -r tools/requirements-e2e.txt
• Run (auto-starts mock server): python3 tools/web_ui_selenium_smoke.py

License

This project is licensed under GPL-3.0. See LICENSE.