Code Documentation

Overview

The OpenTholoMetri firmware runs on an Adafruit Feather M0 microcontroller and performs:

• Periodic sensor readings at configurable intervals (default: 1 minute)
• Timestamped data logging to SD card in CSV format
• Deep sleep between measurements for power efficiency (~6µA in standby)
• Interrupt-driven wake-up via RTC timer

Key Features

• Automated Data Logging: Periodic sensor readings with configurable intervals
• Low Power Operation: Deep sleep mode between readings
• Real-Time Clock: Accurate timestamping using PCF8523 RTC
• Optical Sensing: VCNL4010 proximity and ambient light sensor
• Temperature Monitoring: DS18B20 waterproof temperature probe
• Power Monitoring: Battery voltage tracking
• Interrupt-Driven: RTC timer-based wake-up mechanism

Hardware Architecture

Microcontroller

• Platform: SAMD21-based (Adafruit Feather M0)
• RTC Module: PCF8523 (on Adalogger FeatherWing, I2C address 0x68)
• Storage: SD Card via SPI (on Adalogger FeatherWing)

Pin Configuration

Power Consumption

Firmware Structure

The code is organized into modular components:

• main.ino - Main loop handling sleep, RTC interrupts, and sensor reads
• RTCManager - Manages real-time clock and timer interrupts
• SensorManager - Reads all sensors (proximity, light, temperature, battery)
• SDLogger - Writes timestamped data to SD card in CSV format

Sensor Data

The system reads the following sensors:

• VCNL4010: Proximity and ambient light (I2C address 0x13)
  • Proximity: 0-65535 (higher = more turbid)
  • Ambient Light: 0-65535 (lux-equivalent)
• Grove Turbidity Sensor: Raw ADC value and calculated voltage
• DS18B20: Water temperature in Celsius
• Battery Monitor: Supply voltage monitoring

CSV Output Format

Data is logged with the following columns:

Timestamp,Proximity,Ambient Light,Battery Voltage,Temperature (C),Turbidity Raw,Turbidity Voltage
2024-01-15 10:30:00,245,1023,4.15,22.5,512,2.50

• Timestamp: YYYY-MM-DD HH:MM:SS format
• Proximity/Ambient Light: 0-65535
• Battery Voltage: Volts
• Temperature: Celsius
• Turbidity Raw: Raw ADC value
• Turbidity Voltage: Calculated sensor voltage

Configuration

Changing Logging Interval

Edit Config.h:

const int SLEEP_INTERVAL = 300;  // Change to desired seconds (300 = 5 minutes)

Considerations:

• Shorter intervals: More data collection, higher power consumption, larger files
• Longer intervals: Less frequent data, better battery life, smaller files

Software Installation

Required Libraries

Install via Arduino Library Manager:

1. RTClib by Adafruit
2. Adafruit VCNL4010
3. SD (built-in)
4. SPI (built-in)
5. Wire (built-in)
6. OneWire
7. DallasTemperature

Upload Process

1. Open main.ino in Arduino IDE
2. Select board: Adafruit Feather M0
3. Select port: Your COM port
4. Click Upload
5. Open Serial Monitor (115200 baud) to verify initialization

First-Time Setup

1. Verify RTC: Check Serial output shows RTC initialization success
2. Verify SD Card: Confirm "SD card initialized successfully!" and sensor.csv is created
3. Test Sensor: Check for reasonable proximity and light readings
4. Test Logging: Wait for first RTC interrupt and verify LED flash and data written to SD card

Deployment Configuration

For field deployment:

1. Set desired SLEEP_INTERVAL in Config.h
2. Ensure CR1220 coin cell battery in RTC socket
3. Format fresh SD card (FAT32)
4. Upload final firmware
5. Connect battery and deploy