System Diagrams

This section contains interactive Mermaid diagrams that explain how the Multiflexmeter works at various levels.

Available Diagrams

Understanding the System

Start here if you’re new:

• Measurement Cycle - How the device collects and sends data

Learn how it works:

• Data Flow - How data moves through the system

Development

Building or debugging:

• Communication Sequence - Component interactions and timing
• Error Handling - How errors are detected and handled

Key System Facts

Hardware

• Microcontroller: ATmega1284P @ 8MHz
• Radio: RFM95 (SX1276) LoRa 868MHz
• Memory: 4KB EEPROM for settings
• Sensor: I2C device at address 0x36

Firmware

• Total Code: 704 lines of C++
• Framework: Arduino with PlatformIO
• Main Files:
  • main.cpp (363 lines) - Control logic
  • smbus.cpp (177 lines) - I2C driver
  • rom_conf.cpp (80 lines) - Settings
  • sensors.cpp (23 lines) - Sensor interface

Communication

• I2C: 80kHz bus speed, sensor address 0x36
• LoRaWAN: OTAA, EU868 band, Class A
• I2C Commands:
  • 0x10 (CMD_PERFORM) - Trigger measurement
  • 0x11 (CMD_READ) - Read measurement data
• LoRaWAN Downlink Commands:
  • 0xDEAD - Reset device (5s delay)
  • 0x10 [MSB] [LSB] - Set measurement interval
  • 0x11 [addr] [cmd] [args] - Forward command to I2C sensor

Timing

• Measurement Interval: 20 - 4270 seconds (configurable, bounds-checked)
• Sensor Measurement Wait: 10 seconds (after CMD_PERFORM trigger)
• LoRa TX Time: 60-1500ms (depends on spreading factor SF7-SF12)
• LoRaWAN Join: 5-10 seconds (OTAA)
• Initial Version Delay: 45 seconds after join before first measurement