Plant Health Meter

Plant-health-meter

This repository contains Aalto AAN-C2009 project device hardware configuration and embedded software for a plant health monitoring system based on the ESP32c3 SoC.

Features

• Soil moisture sensing
• Ambient light monitoring
• Temperature and humidity measurement
• Battery-powered operation with charging circuit
• Web interface for monitoring plant health

PCB

PCB design done in KiCad. Schematic: PDF

Key Components

• ESP32-C3 microcontroller
• BME280 temperature/humidity sensor
• Custom capacitive soil moisture sensor
• Photodiode and OPA340 based transimpedance amplifier
• ADS1115 16-bit ADC for accurate measurements

Embedded software

Embedded software is written in C using the ESP-IDF (Espressif IoT Development Framework) ESP programming guide

Pin Assignments

See the schematic for detailed I/O connections and sensor bus configuration.

Setup Instructions

1. Follow the ESP-IDF installation guide
2. Clone this repository
3. In the main/ folder create private_config.h file, with following definitions:
   1. #define FIREBASE_HOST "xxx.firebasedatabase.app" - url of the firebase realtime database
   2. #define FIREBASE_AUTH "" - authentication token for the firebase - (TODO: not tested yet with protected database)
4. Set ESP32-C3 target in the idf idf.py set-target esp32c3
5. Configure the partitions and BLE version idf.py menuconfig:
   1. Go to Partition Table → Partition Table and select Custom partition table CSV. Then set the path to partitions.csv.
   2. Go to Component Config → Bluetooth → Bluedroid BLE version and choose v4.0.
   3. Save and exit the configuration menu.
6. Build and flash using idf.py build flash monitor

Connection Instructions

1. By default, there are no Wi-Fi credentials set. The device will immediately enter Bluetooth setup mode on boot.

2. For setup, you’ll need a mobile app capable of sending data over BLE, such as nRF Connect.

3. When the device is in Bluetooth setup mode, one of its LEDs will begin blinking. You can then find the device in the app under the name:
   PLANT_SENSOR_01

4. Press Connect to establish a Bluetooth connection.

5. Once connected, look for Advertised Services in the device details. Find the characteristic that supports both Read and Write, and tap the up arrow (⬆️) to write data.

6. Select UTF-8 as the encoding format and send a message with the following structure:

   device_id:wifi_ssid:wifi_password

   For example:

   sensor1:mywifi:secret_password

7. After sending the credentials, the device will restart and attempt to connect to the specified Wi-Fi network.

8. Once connected, sensor data will be sent to Firebase under the provided device_id.

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Important Notes:

• device_id can contain only letters, digits, and underscores (e.g., plant_sensor_1).
• If the device fails to connect to Wi-Fi, it will re-enter Bluetooth setup mode on reboot.

Power Requirements

3.7V Li-ion battery or USB power