Suitchi

DIY Smart Switch with HomeKit and Home Assistant support, built on the ESP8266.

Features

• Apple HomeKit — native HomeKit bridge, no hub required. Exposes switch, temperature, humidity, motion, and occupancy as separate accessories
• Home Assistant (MQTT) — optional MQTT integration with autodiscovery. All entities appear automatically in HA with full bidirectional switch control
• Motion & Occupancy Sensor — PIR-based detection (MH-SR602) with instant HomeKit/MQTT notifications on state change
• Temperature & Humidity Sensor — DHT11 with heat index calculation, reported every 10 seconds
• Relay Switch — NO/NC relay controllable from HomeKit, Home Assistant, or the physical button
• OLED Status Screen — 64x48 SSD1306 display showing temperature, humidity, heat index, occupancy, and switch state. Only redraws on state changes to save I2C bandwidth
• Physical Button — single-click to toggle relay, long-press (5s) to reset HomeKit pairing and reboot
• OTA Updates — over-the-air firmware updates via ArduinoOTA with progress displayed on OLED
• Relay State Persistence — switch state is saved to EEPROM and restored on boot, so restarts don't change the light
• Crash Resilience — low-heap watchdog triggers a controlled restart before the device crashes. WiFi connection has a 30-second timeout with automatic reboot on failure
• Remote Diagnostics — HTTP /status endpoint and MQTT diagnostic sensors expose free heap, uptime, HomeKit client count, and last reset reason without needing serial access

Hardware

Component	Description
WeMos D1 Mini Pro V3.0	ESP8266 MCU
MH-SR602	PIR motion sensor
OLED LCD Shield 0.66"	SSD1306 64x48 I2C display
DHT11	Temperature & humidity sensor
Wemos D1 Mini Relay Shield	NO/NC relay output
110v-220v to 5v PSU	AC-DC power supply
OMRON 12x12x6mm	Tactile push button

Full bill of materials with purchase links in sch/README.md. Schematic in sch/, 3D-printable enclosure STLs in stl/.

Pin Assignments

Pin	Function
D8	Relay
D7	Physical switch (INPUT_PULLUP)
D4	DHT11 data
D3	PIR motion sensor
SDA/SCL	OLED I2C

Setup

Prerequisites

Install the following in Arduino IDE:

• Board: ESP8266 board package
• Libraries:
  • Arduino-HomeKit-ESP8266
  • esp8266-oled-ssd1306
  • DHT sensor library
  • PubSubClient (only if using MQTT)

Configuration

Edit src/suitchi/Constants.h:

#define homeKitPin "1CB8"
#define homeKitPassword "111-11-111"
#define bridgeName "Suitchi 1CB8"
#define otaName "suitchi_1CB8"
#define serialNumber "123457"

Edit src/suitchi/wifi_info.h with your WiFi credentials:

const char *ssid = "YourSSID";
const char *password = "YourPassword";

MQTT / Home Assistant (Optional)

To enable MQTT with Home Assistant autodiscovery, uncomment and configure in Constants.h:

#define MQTT_ENABLED

#define MQTT_SERVER         "192.168.1.100"
#define MQTT_PORT           1883
#define MQTT_USER           ""
#define MQTT_PASS           ""
#define MQTT_NODE_ID        "suitchi_1cb8"
#define MQTT_TOPIC_PREFIX   "suitchi/1CB8"
#define MQTT_PUBLISH_INTERVAL 30000

Once connected, the device publishes discovery configs to homeassistant/ and all entities appear automatically in Home Assistant grouped under a single device. The switch supports bidirectional control — toggling from HA, HomeKit, or the physical button keeps all three in sync.

Build & Upload

1. Open src/suitchi/suitchi.ino in Arduino IDE
2. Select board LOLIN(WeMos) D1 mini Pro
3. Upload via USB for initial flash

Subsequent updates can be done over-the-air via ArduinoOTA.

HTTP API

The device runs a web server on port 80:

Endpoint	Description
GET /	Welcome message
GET /TH	JSON temperature and humidity
GET /motion	JSON motion and occupancy state
GET /status	JSON free heap, HomeKit clients, uptime, and reset reason

MQTT Topics

When MQTT is enabled, the following topics are published under the configured prefix (e.g., suitchi/1CB8/):

Topic	Type	Description
status	Availability (LWT)	online/offline — set automatically by broker on disconnect
temperature	State (retained)	Temperature in °C
humidity	State (retained)	Humidity in %
heat_index	State (retained)	Heat index in °C
motion	State (retained)	ON/OFF
occupancy	State (retained)	ON/OFF
switch	State (retained)	ON/OFF
switch/set	Command	Send ON/OFF to control the relay
heap	Diagnostic	Free heap in bytes
uptime	Diagnostic	Seconds since boot
reset_reason	Diagnostic (retained)	Last ESP reset reason

License

MIT

Acknowledgements

• Arduino HomeKit ESP8266
• ThingPulse OLED SSD1306
• esp-homekit
• PubSubClient