Caravan Automation System

Low-power monitoring and automation system for a towable caravan, built around an ESP32-C6 SuperMini running OpenThread Border Router with Matter-compatible sensors.

Project Goals

Monitor battery state, solar production, temperatures, water level, doors, leaks, motion
Detect power source (shore power, car connection, off-grid)
Alert via SMS for critical events (leak, intrusion, low battery)
Display status on local AMOLED screen (T-Encoder Pro)
Control via phone app (BLE) or rotary encoder
Level caravan using gyroscope with audio feedback
Track GPS location while towing
Future-proof for relay control without implementing it now

Architecture Overview

┌─────────────────────────────────────────────────────────────────┐
│                    ESP32-C6 SuperMini HUB                       │
│                                                                 │
│  ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐         │
│  │ Thread │ │ Matter │ │ Wi-Fi  │ │  BLE   │ │ State  │         │
│  │  OTBR  │ │  Ctrl  │ │ + OTA  │ │  C+P   │ │Machine │         │
│  └────┬───┘ └────┬───┘ └────────┘ └────┬───┘ └────────┘         │
│       │          │                     │                        │
│  ┌────┴──────────┴───┐  ┌──────────────┴───┐  ┌────────┐        │
│  │ 802.15.4 Radio    │  │ BLE 5.3 Radio    │  │ VE.Dir │        │
│  │ (native)          │  │                  │  │ Parser │        │
│  └────┬──────────────┘  └────┬─────────────┘  └────┬───┘        │
└───────┼──────────────────────┼─────────────────────┼────────────┘
        │                      │                     │
        ▼                      ▼                     ▼
   ┌─────────┐            ┌─────────┐           ┌─────────┐
   │  IKEA   │            │ Power   │           │ Victron │
   │ Thread  │            │ Queen   │           │  MPPT   │
   │ Sensors │            │  BMS    │           │VE.Direct│
   └─────────┘            └─────────┘           └─────────┘

Hardware Components

Component	Purpose	Interface
ESP32-C6 SuperMini	Main controller (Thread + Wi-Fi + BLE + Matter)	—
T-Encoder Pro	AMOLED display + rotary encoder + buzzer	UART (JST)
SIM7600SA-MNSE	4G LTE + GPS	UART (AT mode + GPS-via-AT)
MPU6500	Gyroscope/accelerometer	I2C
Victron MPPT 75/15	Solar charge controller	VE.Direct
Victron IP65 12V 25A	Shore power charger	—
Power Queen 100Ah	LiFePO4 battery with BLE BMS	BLE
Dometic SMP 301-01	230V AC → 12V DC	—
13-pin Euro connector	Tow vehicle interface	—
Water level gauge	0-190Ω resistive	ADC
SimBase data SIM	4G connectivity	—
INA219 ×2	Current/power monitor (main bus, fridge)	I2C
PC817 ×3	Optocoupler isolation (shore/car detect)	GPIO
HLK-PM01	230V AC → 5V DC for shore detection	—
AO3401	P-channel MOSFET, SIM7600 power gate	GPIO
TXS0102	Bidirectional level shifter (VE.Direct)	—
DS18B20	Waterproof outdoor temp sensor	1-Wire
IKEA TIMMERFLOTTE	Indoor temp/humidity	Thread
IKEA MYGGBETT ×2	Door/window sensor	Thread
IKEA KLIPPBOK	Water leak sensor (built-in siren)	Thread
IKEA MYGGSPRAY	Motion sensor	Thread
Resistors, JST-PH connectors, prototype PCB	Assembly	—

GPIO Assignments

GPIO	Function	Direction	Protocol	Notes
0	Water level	Input	ADC	A0, voltage divider
1	Shore power detect	Input	GPIO	Active LOW (PC817)
2	Car connection detect	Input	GPIO	Active LOW (PC817)
3	DS18B20 outdoor temp	Bidir	1-Wire	4.7 kΩ pull-up to 3.3V
4	I2C SDA	Bidir	I2C	INA219 ×2, MPU6500
5	I2C SCL	Output	I2C	400 kHz
6	LP_UART RX	Input	UART	SIM7600 → C6
7	LP_UART TX	Output	UART	C6 → SIM7600, 115200 baud
8	SIM7600 power gate	Output	GPIO	AO3401 P-FET (disables onboard RGB LED)
14	Reserved	—	—	Future relay channel
20	UART1 RX	Input	UART	VE.Direct from MPPT, 19200 baud
21	UART1 TX	Output	UART	VE.Direct via TXS0102 level shifter
22	T-Encoder TX	Output	SW UART	JST connector to display
23	T-Encoder RX	Input	SW UART	115200 baud
USB	USB-Serial-JTAG	—	USB	Flashing + console + JTAG
BLE	Power Queen + Phone	—	BLE 5.3	Central + Peripheral
RF	IKEA sensors	—	802.15.4	Native, Matter-over-Thread

Reserved / cannot use: GPIO 9 (BOOT button), 12, 13 (USB D-/D+), 15 (status LED), 18, 19 (internal SPI flash).

I2C Device Addresses

Address	Device	Data
0x40	INA219 #1	Main bus voltage, current, power
0x41	INA219 #2	Fridge circuit voltage, current, power
0x68	MPU6500	Pitch, roll, acceleration

Detection Circuits

Shore Power Detection (230V AC)

230V AC ──► HLK-PM01 ──► 5V ──► 1kΩ ──► PC817 LED
                                              │
                                             GND

3.3V ──► 10kΩ pull-up ──┬──► GPIO1
                        │
                   PC817 collector
                        │
                       GND

Logic: Shore ON → GPIO1 LOW | Shore OFF → GPIO1 HIGH

Car Connection Detection (13-Pin Connector)

Pin 10 (12V) ──► 10kΩ ──┬──► 10kΩ ──► GND     (voltage divider)
                        │
                        └──► 1kΩ ──► PC817 LED
                                          │
                                         GND

3.3V ──► 10kΩ pull-up ──┬──► GPIO2
                        │
                   PC817 collector
                        │
                       GND

Logic: Car ON → GPIO2 LOW | Car OFF → GPIO2 HIGH

Water Level Sensing

3.3V ──► 100Ω ──┬──► GPIO0 (ADC)
                │
           Tank Sensor (0-190Ω)
                │
               GND

Voltage: Empty (0Ω) = 0.00V | Full (190Ω) = 2.16V
ADC: Empty ≈ 0 | Full ≈ 2680 (of 4095)

Outdoor Temperature (DS18B20)

3.3V ──► 4.7kΩ ──┬──► GPIO3 (1-Wire data)
                 │
            DS18B20 DATA (yellow)
            DS18B20 VCC (red) ──► 3.3V
            DS18B20 GND (black) ──► GND

VE.Direct Connection

Victron MPPT uses 5V TTL; ESP32-C6 uses 3.3V. Level shifter required.

Victron JST-PH          TXS0102              ESP32-C6
─────────────          ─────────             ────────
Pin 1: GND ──────────► GND ◄────────────────► GND
Pin 2: RX  ◄───────── HV1 ◄──── LV1 ◄─────── GPIO21 (TX)
Pin 3: TX  ──────────► HV2 ────► LV2 ───────► GPIO20 (RX)
Pin 4: +5V ──────────► HV (ref)
                       LV (ref) ◄───────────► 3.3V

State Machine

GPIO1 (Shore)	GPIO2 (Car)	State	Description
HIGH	HIGH	OFFGRID	Battery only, wild camping
LOW	HIGH	CAMPSITE	Shore power connected
HIGH	LOW	TOWING	Car connected, driving
LOW	LOW	ARRIVED	Both connected, just parked

State Behaviors

Feature	OFFGRID	CAMPSITE	TOWING	ARRIVED
Sleep mode	Light sleep	Off	Off	Off
GPS tracking	On request	Off	Continuous	Off
Motion alerts	On	Optional	Suppressed	Off
Sway detection	Off	Off	Active	Off
Leveling mode	Off	On request	Off	Active
Display	On-demand	Always on	Speed/stability	Always on
SIM7600	Power-gated	Power-gated	On	Power-gated

Data Points

Thread Sensors (IKEA Matter-over-Thread)

Sensor	Model	Data	Location
Indoor climate	TIMMERFLOTTE	Temperature, humidity	Living area
Main door	MYGGBETT	Open/closed	Entry door
Storage door	MYGGBETT	Open/closed	External storage
Water leak	KLIPPBOK	Leak detected, built-in siren	Under sink
Motion	MYGGSPRAY	Motion detected	Living area

Wired Sensors

Sensor	Interface	Data
Outdoor temp	DS18B20 (1-Wire)	Temperature °C
Water tank	Resistive (ADC)	Level 0-100%
Main current	INA219 #1 (I2C)	Voltage, current, power
Fridge current	INA219 #2 (I2C)	Voltage, current, power
Pitch/Roll	MPU6500 (I2C)	Orientation, acceleration

BLE Sensors

Sensor	Protocol	Data
Power Queen BMS	BLE (proprietary)	SoC, voltage, current, cell voltages, temp, cycles

Serial Sensors

Sensor	Interface	Data
Victron MPPT	VE.Direct (UART)	Panel V/I, battery V/I, yield, charge state
SIM7600 GPS	USB (NMEA)	Latitude, longitude, speed, heading

Communication Protocols

Link	Protocol	Speed	Purpose
C6 ↔ Victron MPPT	UART1	19200	VE.Direct text protocol
C6 ↔ T-Encoder Pro	SW UART	115200	JSON status + buzzer commands
C6 ↔ SIM7600	LP_UART	115200	AT commands, SMS, GPS-via-AT
C6 ↔ Power Queen	BLE	—	Proprietary BMS protocol
C6 ↔ Phone	BLE GATT	—	Status read, config write
C6 ↔ IKEA sensors	802.15.4 (Matter)	—	Native, no RCP
C6 ↔ Wi-Fi AP	Wi-Fi 6 STA	—	OTA + home backhaul

T-Encoder Pro Protocol

C6 → T-Encoder (status updates + buzzer)

{
  "ts": 1711700000,
  "state": "CAMPSITE",
  "battery": {"soc": 78, "voltage": 13.2, "current": 2.5, "power": 33},
  "solar": {"voltage": 18.5, "power": 45, "daily": 320},
  "temp": {"indoor": 22.5, "outdoor": 18.2, "humidity": 55},
  "water": {"level": 65},
  "doors": {"main": "closed", "storage": "closed"},
  "level": {"pitch": 1.2, "roll": -0.5}
}

Buzzer commands (sent in addition to status updates — display fires its onboard buzzer):

{"buzzer": {"pattern": "level_ok"}}
{"buzzer": {"pattern": "level_warning"}}
{"buzzer": {"pattern": "alert"}}
{"buzzer": {"freq": 2000, "duration_ms": 100}}

T-Encoder → C6 (user input)

{"event": "encoder", "direction": "cw", "clicks": 3}
{"event": "button", "action": "press"}
{"event": "button", "action": "long_press"}
{"event": "touch", "x": 120, "y": 80}
{"event": "menu", "select": "level_mode"}

SMS Commands

Command	Response
`STATUS`	Battery SoC, voltage, solar power, temperatures, GPS
`POWER`	Detailed power info (main bus, fridge, charging)
`GPS`	Coordinates + Google Maps link
`HELP`	List available commands

Alert Conditions (Configurable)

Condition	Default Threshold	Action
Low battery	SoC < 20%	SMS alert
Water leak	Detected	SMS alert + buzzer
Door open (OFFGRID)	Any door	SMS alert
Motion (OFFGRID)	Detected	SMS alert
Excessive sway	> 0.3g lateral	Buzzer warning
High temperature	> 35°C indoor	SMS alert
Freezing risk	< 5°C indoor	SMS alert

Power Budget

State	Mode	Estimated avg current	Notes
OFFGRID	Light sleep, Thread router awake	30–50 mA	Conservative; instrument early in firmware
CAMPSITE	Active, Wi-Fi connected	80–120 mA	Display always on
TOWING	Active, GPS continuous	100–150 mA	SMS standby
ARRIVED	Active, similar to CAMPSITE	80–120 mA

With a 100 Ah battery: roughly 80–140 days OFFGRID standby. The previous architecture's ~520 day figure assumed the host MCU could deep-sleep, which is incompatible with running a Thread border router. These numbers will be measured and refined during firmware bring-up.

Repository Layout

.
├── README.md                       # This document
│
├── c6-hub/                         # ESP-IDF v6.0 firmware (ESP32-C6)
│   ├── CMakeLists.txt
│   ├── partitions.csv              # Single-app slot for 4 MB; switches to dual-OTA on 16 MB
│   ├── sdkconfig.defaults
│   ├── build.sh                    # Wraps idf.py
│   ├── flash.sh                    # Wraps idf.py flash + monitor
│   └── main/
│       ├── CMakeLists.txt
│       ├── main.c                  # Entry point — currently boot info + heartbeat
│       ├── state_machine.c         # OFFGRID / CAMPSITE / TOWING / ARRIVED  (planned)
│       ├── thread_otbr.c           # OpenThread Border Router  (planned)
│       ├── matter_controller.c     # Matter device pairing + reads  (planned)
│       ├── wifi_manager.c          # Wi-Fi STA + OTA  (planned)
│       ├── ota_handler.c           # esp_https_ota driver  (planned)
│       ├── victron_vedirect.c      # VE.Direct parser  (planned)
│       ├── power_monitor.c         # INA219 + shore/car detect  (planned)
│       ├── sensors.c               # DS18B20, water level, MPU6500  (planned)
│       ├── ble_bms.c               # Power Queen BMS client  (planned)
│       ├── ble_server.c            # Phone-app GATT server  (planned)
│       ├── sms_handler.c           # SIM7600 AT commands  (planned)
│       ├── gps.c                   # GPS-via-AT polling  (planned)
│       ├── display_link.c          # T-Encoder UART protocol + buzzer  (planned)
│       ├── alerts.c                # Threshold monitoring  (planned)
│       ├── rules_engine.c          # Configurable automation  (planned)
│       └── config.c                # NVS storage for settings  (planned)
│
├── t-encoder-display/              # LVGL UI for T-Encoder Pro  (planned)
│   ├── main.cpp
│   ├── gauges.cpp
│   ├── level_screen.cpp
│   ├── menu.cpp
│   └── uart_protocol.cpp
│
├── docs/                           # Architecture & protocol specs
│   ├── architecture.mermaid
│   ├── state_machine.mermaid
│   ├── wiring.mermaid
│   ├── dataflow.mermaid
│   ├── protocols/
│   │   ├── powerqueen_bms.md
│   │   └── victron_instant_readout.md
│   └── superpowers/                # Specs and plans for major changes
│       ├── specs/
│       └── plans/
│
└── tools/
    └── ble-probe/                  # Python reference (Pi-based) — reverse-engineers
        ├── read_battery.py         # the BLE protocols the firmware re-implements in C.
        ├── read_victron.py         # Not part of the runtime system.
        └── victron.env.example

Module source files inside c6-hub/main/ (other than main.c) and t-encoder-display/ are targets to be implemented — main.c is a hello-world that prints chip info; the rest will be built up module by module, each with its own spec under docs/superpowers/specs/.

Key Design Decisions

Single ESP32-C6 SuperMini — One chip handles Thread (native 802.15.4), Wi-Fi 6, BLE 5.3, and the application logic. Replaces the earlier ESP32-S3 + XIAO nRF52840 RCP design; see docs/superpowers/specs/2026-04-25-c6-single-mcu-design.md for the rationale.
IKEA Thread sensors over custom nodes — Off-the-shelf Matter-over-Thread devices eliminate custom firmware, provide multi-year battery life, and simplify deployment.
SIM7600 over UART (AT mode + GPS-via-AT) — The C6 has no USB host. AT-mode polling at ~1 Hz is sufficient for the caravan use case (SMS commands, periodic GPS); avoids a second UART for raw NMEA streaming.
T-Encoder Pro for display and audio — The display module includes its own ESP32-S3, AMOLED screen, rotary encoder, and a buzzer on its GPIO17. The C6 sends JSON over UART; the display drives its own UI and sounds its own buzzer. No discrete buzzer needed on the C6.
Single Victron VE.Direct — MPPT only; IP65 charger data is redundant given shore power detection and INA219 monitoring.
DS18B20 for outdoor temp — Wired sensor is more reliable than battery-powered Thread sensor for external mounting.
Power Queen BMS via BLE — Deferred to software phase due to proprietary protocol; INA219 provides backup current measurement.
Relay support pre-wired — GPIO 14 reserved for future relay control without implementing now.
Automation rules in software — All thresholds and behaviors configurable in NVS, changeable via phone app or Wi-Fi.
Wi-Fi kept active — Used for OTA updates and home-network connectivity when parked. Drops to backhaul-only or disabled if SRAM headroom becomes a problem.

Next Steps

~~Flash XIAO nRF52840 with OpenThread RCP firmware~~ — obsolete after C6 pivot.
Bring up c6-hub hello-world firmware on the 4 MB ESP32-C6FH4 — confirm USB-Serial-JTAG flash + console + IEEE 802.15.4 MAC visible. ✓ Done 2026-04-25.
Build VE.Direct cable with TXS0102 level shifter.
Wire detection circuits (shore power, car connection).
Develop ESP32-C6 firmware modules — each with its own spec/plan under docs/superpowers/. Suggested order: state_machine → power_monitor → sensors → display_link → ble_bms → thread_otbr → matter_controller → wifi_manager → sms_handler → ota_handler → alerts/rules.
Pair IKEA sensors to the Thread network (after Matter controller works).
Develop T-Encoder Pro UI (LVGL gauges, menus, buzzer patterns).
Port Power Queen BLE protocol to C (spec in docs/protocols/powerqueen_bms.md).
Migrate to 16 MB SuperMini when it arrives — switch partitions.csv to dual-OTA layout.
Test and iterate.

References

Document version: 2.0 — single-MCU ESP32-C6 architecture
Last updated: April 2026

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Caravan Automation System

Project Goals

Architecture Overview

Hardware Components

GPIO Assignments

I2C Device Addresses

Detection Circuits

Shore Power Detection (230V AC)

Car Connection Detection (13-Pin Connector)

Water Level Sensing

Outdoor Temperature (DS18B20)

VE.Direct Connection

State Machine

State Behaviors

Data Points

Thread Sensors (IKEA Matter-over-Thread)

Wired Sensors

BLE Sensors

Serial Sensors

Communication Protocols

T-Encoder Pro Protocol

C6 → T-Encoder (status updates + buzzer)

T-Encoder → C6 (user input)

SMS Commands

Alert Conditions (Configurable)

Power Budget

Repository Layout

Key Design Decisions

Next Steps

References

About

Releases

Packages

Contributors

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Name		Name	Last commit message	Last commit date
c6-hub		c6-hub
docs		docs
t-encoder-display		t-encoder-display
tools/ble-probe		tools/ble-probe
.gitignore		.gitignore
README.md		README.md

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Caravan Automation System

Project Goals

Architecture Overview

Hardware Components

GPIO Assignments

I2C Device Addresses

Detection Circuits

Shore Power Detection (230V AC)

Car Connection Detection (13-Pin Connector)

Water Level Sensing

Outdoor Temperature (DS18B20)

VE.Direct Connection

State Machine

State Behaviors

Data Points

Thread Sensors (IKEA Matter-over-Thread)

Wired Sensors

BLE Sensors

Serial Sensors

Communication Protocols

T-Encoder Pro Protocol

C6 → T-Encoder (status updates + buzzer)

T-Encoder → C6 (user input)

SMS Commands

Alert Conditions (Configurable)

Power Budget

Repository Layout

Key Design Decisions

Next Steps

References

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