Environment sensor module based on the ESP32-Wroom Module

Overview

This environment sensor is intended to be a low cost sensor that can be deployed throughout the environment controlled by the RaspiCool system.

Recommended sensor locations

• One sensor for each room
  • Thermostat includes a sensor and only needs a sensor module if drafts, etc. make the built-in sensor unreliable.
• One sensor for each return air vent
• One sensor in the vent closest to the AC coil
  • This sensor, combined with the return air sensors, is used to track 'delta-t', which can help indicate system troubles.

Hardware description

The sensor module is built using an esp32-wroom module, providing encryption, wifi, and bluetooth capabilities. The primary sensor included is the BME280, providing temperature, humidity, and pressure data. Power is provided by an 18650 battery.

Sensor Options

• Option to include SSD1306 oled display
• SPI and I2C expansion points included on sensor pcb

Usage

Sensor pairing

The base sensor image does not include any wifi configuration or authentication certificates. When the sensor is powered in this state, it will scan bluetooth looking for a RaspiCool thermostat. When it finds one, it will trigger a popup on the thermostat to confirm pairing the sensor.

• Note: The thermostat must be set into pairing mode in order to pair additional sensors. Bluetooth is normally off on the thermostat.

Pairing causes the following events:

• Wifi configuration is sent via bluetooth to the sensor
• Thermostat will assign a static IP and set a static DHCP reservation for the sensor
• Sensor receives IP via DHCP and verifies the address with the thermostat registration service
• Client authentication certificates are generated and delivered to the sensor
• Sensor retrieves additional configuration from the thermostat services
• Sensor resets and starts normal data loop

Sensor operation

In normal operation, the sensor spends the majority of the time in a sleep state. During each wake cycle, the following events happen:

• Read sensor values
• Cache current value
• Determine if values need to be reported - Enter sleep at this point if no reporting needed
  • Sensor values have changed by more than threshhold (Default 0.1c, 0.5%)
  • Reporting cycle time has expired (Default 1 minute)
• Bring wifi online
• Connect to thermostat
• Send sensor data
• Check for commands (Update, config, etc.)
• Enter sleep

TODO: Thermostat data via https api instead of mqtt?

How to install this app

• mos build
• mos flash

Helpful commands

• See bashaliases.sh for information

Built for (MongooseOS)[https://mongoose-os.com]