Busroot DAU Firmware

Firmware to turn the Arduino Opta into a robust, easy-to-use, data aquisition unit (DAU) for industrial analytics. Featuring simple input handling, MQTT communication, and 1000-frame circular buffer for maximum reliability in the case of connection drops.

Supports communication over WiFi, Ethernet and the Blues Wireless for Opta (Cellular) device.

Firmware can be uploaded from a web browser using WebDFU: https://outputindustries.github.io/busroot-dau/

Who is this for?

Anyone looking for a reliable and straightforward way to capture data points from a shop floor or industrial environment.

Features

Input Capabilities

• Support for pulse counting and state readings on inputs 1 to 6.
• Analog readings (12-bit, 0-4095 range) on inputs 7 and 8.
• Communication with Energy Meters over Modbus.

Communication

• MQTT support over WiFi, Ethernet, or Blues Wireless for Opta
• Modbus RTU support for energy meters (19200 baud)
• Serial console for configuration and debugging
• JSON message format

Reliability Features

• 1000-frame circular buffer on M4 core (83 minutes @ 5s intervals)
• Watchdog protection on both cores
• Lock-free circular buffer for safe dual-core communication
• Race-condition-free counter implementation
• Configuration persistence in flash memory
• Automatic MQTT reconnection on connection failure

Quick Start

1. Visit https://outputindustries.github.io/busroot-dau/
2. Chose to configure via the webpage, or configure via serial.
3. Double-tap reset button to enter bootloader mode.
4. Upload firmware.

Project Structure

busroot-dau/
├── src/
│   ├── m4.cpp              # M4 core: Input reading
│   ├── m7.cpp              # M7 core: Networking & MQTT
│   ├── data_frame.h/cpp    # Inter-core communication
│   ├── config.h/cpp        # Configuration management
│   └── status.h/cpp        # Status & error handling
├── web/
│   ├── index.html          # Web interface
│   ├── css/styles.css      # Styling
│   ├── js/app.js           # JavaScript
│   └── firmwares/          # Auto-generated binaries
├── platformio.ini          # Build configuration
├── copy_firmware.py        # Post-build script
└── README.md               # This file

MQTT Message Format

Without Modbus

{
  "ver": "v0.1.0",
  "rssi": -65, // WiFi Signal Strength (dB)
  "cb": 10,    // User Button Count
  "c1": 5,     // Input 1 Count
  "c2": 0,     // Input 2 Count
  "c3": 0,     // Input 3 Count
  "c4": 0,     // Input 4 Count
  "c5": 0,     // Input 5 Count
  "c6": 0,     // Input 6 Count
  "sb": 1,     // User Button State
  "s1": 0,     // Input 1 State
  "s2": 0,     // Input 2 State
  "s3": 0,     // Input 3 State
  "s4": 0,     // Input 4 State
  "s5": 0,     // Input 5 State
  "s6": 0,     // Input 6 State
  "a7": 12,    // Input 7 Analog
  "a8": 0      // Input 8 Analog
}

With Modbus Energy Meter

{
  "ver": "v0.1.0",
  "rssi": -65,
  "cb": 10,
  ...
  "p1v1": 230.5,  // Modbus Device 1 - Phase 1 Volts
  "p2v1": 231.2,  // Modbus Device 1 - Phase 2 Volts
  "p3v1": 229.8,  // Modbus Device 1 - Phase 3 Volts
  "p1a1": 5.4,    // Modbus Device 1 - Phase 1 Amps
  "p2a1": 4.9,    // Modbus Device 1 - Phase 2 Amps
  "p3a1": 5.1,    // Modbus Device 1 - Phase 3 Amps
  "pf1": 0.95,    // Modbus Device 1 - Power Factor
  "kWh1": 1234.5  // Modbus Device 1 - Kilowatt-hours (Meter Reading)
}

Published to: {prefix}/busroot/v2/dau/{deviceId}

Configuration

Configuration is stored in flash memory and persists across reboots.

Troubleshooting

Device won't connect to WiFi

• Check SSID and password
• Verify 2.4GHz network (5GHz not supported)
• Check signal strength
• Try increasing WiFi retry attempts in code

Messages not appearing in MQTT

• Verify broker address and port
• Check username/password
• Ensure topic permissions
• Monitor buffer status via serial

Missing input pulses

• Check debounce delay (50ms default)
• Verify input wiring
• Monitor serial output
• Reduce send interval if needed

Device resets unexpectedly

• Check watchdog timeout settings
• Verify power supply stability
• Monitor error codes on LEDs (D0-D3)

Status LEDs

The device uses LEDs D0-D3 to show status codes in binary:

Code	Meaning
1	WiFi Connecting
2	Ethernet Connecting
3	MQTT Connecting
4	Running (normal)
8	MQTT Publishing
9	Config Load Error
10	WiFi Failed
11	MQTT Failed
12	Publish Failed

RGB LED shows error state (red) or normal operation.

Development

Building

pio run                    # Build both cores
pio run -e opta_m7        # Build M7 only
pio run -e opta_m4        # Build M4 only

Uploading

pio run -e opta_m7 -t upload
pio run -e opta_m4 -t upload

Monitoring

pio device monitor -b 19200

Clean Build

pio run -t clean
pio run

Technical Specifications

• Version: 5
• Platform: STM32H747XIH6 (480MHz dual-core)
• Framework: Arduino (Mbed OS)
• Send Interval: 5 seconds (configurable)
• Debounce Delay: 50ms (configurable)
• Buffer Capacity: 1000 frames (83 minutes @ 5s intervals)
• Serial Baud: 19200
• Modbus Baud: 19200 (8N1)

Attributions

• WebDFU - https://github.com/devanlai/webdfu