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Multiflexmeter

Quick Start Guide

This guide walks you through setting up a Multiflexmeter device from scratch.

Prerequisites

Section titled “Prerequisites”

Hardware

Section titled “Hardware”
  • Multiflexmeter V3 board (ATmega1284P)
  • USBasp ISP programmer
  • FTDI USB-to-Serial adapter (for debugging)
  • Sensor module (I2C address 0x36)

Software

Section titled “Software”
  • PlatformIO (VS Code extension recommended)
  • Git (for cloning the repository)

Setup Steps

Section titled “Setup Steps”

  1. Clone the Repository

    Terminal window
    git clone https://github.com/your-org/Multiflexmeter.git
    cd Multiflexmeter

  2. Initialize Submodules

    The LMIC library is included as a Git submodule:

    Terminal window
    git submodule update --init

  3. Build the Firmware

    Terminal window
    pio run

    This compiles the firmware for the mfm_v3_m1284p board target.

  4. Program EEPROM Credentials

    Before flashing, you must program the EEPROM with LoRaWAN credentials. Create a programmer sketch:

    #include <EEPROM.h>
    

    // Get these from The Things Network console
    const uint8_t APP_EUI[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // LSB first
    const uint8_t DEV_EUI[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // LSB first
    const uint8_t APP_KEY[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; // MSB first
    

    void setup() {
      // Magic bytes
      EEPROM.write(0, 'M');
      EEPROM.write(1, 'F');
      EEPROM.write(2, 'M');
      EEPROM.write(3, 0);
    

      // HW Version (1.0)
      EEPROM.write(4, 0x10);  // MSB: major=1, proto=0
      EEPROM.write(5, 0x00);  // LSB: minor=0, patch=0
    

      // APP_EUI (8 bytes at offset 6)
      for (int i = 0; i < 8; i++) EEPROM.write(6 + i, APP_EUI[i]);
    

      // DEV_EUI (8 bytes at offset 14)
      for (int i = 0; i < 8; i++) EEPROM.write(14 + i, DEV_EUI[i]);
    

      // APP_KEY (16 bytes at offset 22)
      for (int i = 0; i < 16; i++) EEPROM.write(22 + i, APP_KEY[i]);
    

      // Measurement interval: 300 seconds (0x012C)
      EEPROM.write(38, 0x01);  // High byte
      EEPROM.write(39, 0x2C);  // Low byte
    

      // TTN Fair Use Policy: enabled
      EEPROM.write(40, 1);
    

      // Wheel teeth count: 91
      EEPROM.write(41, 91);
    }
    

    void loop() {}

  5. Flash the Firmware

    Connect the USBasp programmer and flash:

    Terminal window
    pio run -t upload

  6. Verify Operation

    Connect the FTDI adapter and monitor serial output:

    Terminal window
    pio device monitor

    You should see:

    • Build date/time on startup
    • LMIC initialization messages
    • Join request attempts
    • “EV_JOINED” when successfully connected to TTN

Register Device on TTN

Section titled “Register Device on TTN”

  1. Log in to The Things Network Console

  2. Create or select an application

  3. Register a new device with:

    • Activation mode: OTAA
    • LoRaWAN version: 1.0.x
    • Regional Parameters: EU868

  4. Copy the credentials:

    • AppEUI: Use LSB format (reversed byte order)
    • DevEUI: Use LSB format (reversed byte order)
    • AppKey: Use MSB format (same as shown)

Troubleshooting

Section titled “Troubleshooting”
IssuePossible CauseSolution
No serial outputDebug disabledEnable #define DEBUG in include/config.h
”EV_JOIN_FAILED”Wrong credentialsVerify EEPROM contents match TTN registration
No join attemptsRadio not respondingCheck SPI connections to RFM95
Immediate resetWatchdog timeoutCheck power supply, verify LMIC init

Next Steps

Section titled “Next Steps”