yagds

This project is yet another garage door sensor.

Sensor data of changing door positions are captured by two reed sensors connected to a ESP-01 module and forwarded using the MQTT to a MQTT broker. A Python script subscribes to these MQTT messages and implements a state machine representing the state of the door (open, closed, moving). If the state of the door changes a Telegram Bot notifies Telegram clients connected to it.

By using Telegram to distribute changes, the MQTT broker does not need to be accessible from the internet. Also the Android Telegram Bot supports Android Auto, so the garage door state can easily be sent to your car.

Hardware

ESP-01 module

The hardware is based on the ESP-01 module using the microchip ESP8266 microcontroller. This microchip includes a micro controller with WIFI and TCP/IP capabilities and can be programmed with the Arduino tool chain. The ESP-01 provides easy access to 8 of the pins of the microchip of which up to 4 can be used as general purpose input/output (GPIO): GPIO0, GPIO2, TX(GPIO1), RX(GPIO3)

But the voltage level of some of the GPIO pins are used to select the boot mode during power-up/after a reset. The configuration which finally worked for me, is using GPIO0 and GPIO3 and make sure, that they are at high voltage level (3.3 V) during reset.

Carrier Board

The micro controller should go to deep sleep mode after the door reached the open or closed position. This saves energy if the hardware should be powered by battery. To wake-up it up again, changes at the reed contacts should trigger a pulse on the RST pin. Based on the idea described here (in German) for both, GPIO0 and RX, a XOR gate is used to compare the signal with a delayed one. The latter is produced by RC-circuits. If the signal changes, the delayed signal keeps is different from the un-delayed signal and the XOR gate outputs one (the two gates in the top left part of the schematics below). If at least one of the signals has changed its state, the output of the OR gate is one. The output of the OR gate is inverted by another XOR gate (top right of the schematics) and used as input for the RST (reset) pin.

To make sure, that the GPIO pins are at high voltage to boot correctly the output of the OR gate is delayed by another RC circuit and ORed with the signals of the GPIO pins. So these pins stay at high until the boot-up has been completed.

The RC circuits and the OR/XOR gates together with a voltage regulator for the 3.3 V power supply of the gates and ESP-01 are combined on a PCB board which carry the ESP-01.

The cables of the reed contacts are connected with RCA (cinch) connectors to the carrier board. A micro USB socket is used for power supply.

The schematics and PCB layout can be found in folder layout_kicad. They were created using KiCad

Software

ESP-01 Firmware

The firmware of the ESP-01 is developed using PlatformIO.

The communication with the MQTT broker and the handling of configuration data (including updating them over the air/the MQTT broker) is handled by the library Homie.

The library simpleTimer is used to timeout connection setup and putting the micro controller into deep sleep state.

LED debug output flashing patterns are generated using the library jled.

To set the configuration, add the file data/homie/config.json and upload it the ESP-01 using Upload SPIFFS image.

{
  "name": "YAGDS",
  "device_id": "door_sensor",
  "device_stats_interval": 60,
  "wifi": {
    "ssid": "xxx",
    "password": "yyy"
  },
  "mqtt": {
    "host": "alpha",
    "port": 8883,
    "base_topic": "homie/",
    "auth": true,
    "username": "aaa",
    "password": "bbb",
    "ssl": true,
    "ssl_fingerprint": "123456789abcedf"
  },
  "ota": {
    "enabled": false
  },
  "settings": {
    "sensor_update_interval": 2,
    "max_resend": 5,
    "connection_timeout": 30,
    "sleep_timeout": 10
  }
}

Known issues:

• My board is affected by this bug, which requires patching the ESP8266 core for Arduino.
• To use SSL fingerprints for the connection between the ESP-01 and a MQTT broker, a special build flag has to set: build_flags = -DASYNC_TCP_SSL_ENABLED=1. Also consider this issue.

Telegram Bot with state machine

A Python script determines the state of the door and sends out messages if the state changes. paho-mqtt is used to subscribe to the MQTT broker to receive the message from the ESP-01. The transitions between different states of the door are followed using the library transitions. Message of the current signal of the reed contacts can trigger changes between the different door states as shown in the picture below.

If a transition causes a state change, also message is sent using the Python Telegram Bot library.

The bot.py scripts looks for the configuration file .mqtt_telegram_bot.ini in the $HOME directory of the user, or for the file specified with the option -c at startup. It contains information about the connection to the MQTT broker and the Telegram Bot.

[MQTT]
broker = broker.address
ca = ~/mqtt_ca.crt
username = username
password = password
topics_path = homie/door_sensor/reeds/#

[Telegram]
token = TOKEN
chat_id = 12345

Authors

• Joachim Herb - jmozmoz

License

This project is licensed under GPL v3