🌉 CanMQTT-Bridge

High-Performance, Bi-Directional Gateway between CAN Bus and MQTT.

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📖 Overview

CanMQTT-Bridge is a production-ready Go application designed to bridge low-level CAN (Controller Area Network) hardware with high-level MQTT IoT networks.

It lets you control motors, read sensors, and monitor robots/vehicles using simple JSON over MQTT.

The bridge handles all binary translation, scaling, and protocol conversion automatically.

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🏗️ System Architecture

The bridge is optimized for high throughput and low latency using Go concurrency.

✔️ Worker Pool Design

• Dedicated CAN workers
• Dedicated MQTT workers
• Prevents blocking & CPU starvation

✔️ SocketCAN Integration

• Direct Linux kernel CAN interface (e.g., can0)

✔️ Dynamic Translation

• JSON configuration maps binary CAN frames → readable JSON

✔️ Filtering

• Only subscribes to CAN IDs defined in config
• Reduces CPU usage

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✨ Key Features

1. 🔄 Bi-Directional Translation

CAN → MQTT

• Reads CAN frames
• Converts binary data to JSON
• Applies scaling factors
• Publishes to MQTT topic

MQTT → CAN

• Receives JSON commands
• Converts scaled values back to raw binary
• Sends CAN frames to bus

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2. 🎛️ Hot-Reload & Runtime Control

Via MQTT topic: translater/run

Controlled at runtime:

• Reload config instantly
• Change debug level
• Set artificial sleep time for throttling

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3. ⏱️ CAN Bus Synchronization (Heartbeat)

Bridge acts as time master.

• CAN ID: 0x5
• Frequency: 100ms
• Sends UNIX timestamp (nanoseconds)

Used for: microcontroller time sync.

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4. 🏥 System Health Monitoring

Publishes telemetry to translater/status:

• CPU Load
• RAM Usage
• CPU Temperature
• Uptime

Useful for Raspberry Pi deployments.

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⚙️ Configuration (messages_config.json)

Defines how CAN frames map to JSON.

Example Item

{
  "topic": "motor/data",
  "canid": "0x63",
  "length": 8,
  "payload": [
    { "key": "rpm", "type": "int16_t", "place": [2, 4], "factor": 1.0 },
    { "key": "torque", "type": "float", "place": [4, 8], "factor": 0.001 }
  ]
}

Process Example

Incoming CAN (ID 0x63):

[0x00, 0x00, 0xE8, 0x03, 0x00, 0x40, 0x1C, 0x46]

Extracted:

• RPM = 1000
• Torque = 10.0

Outgoing MQTT:

{"rpm": 1000, "torque": 10.0}

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📡 Internal MQTT System Topics

1. translater/status

Direction: Bridge → MQTT

Provides:

• cpu_load
• ram_usage
• cpu_temp
• uptime

2. translater/run

Direction: MQTT → Bridge

Commands:

• reload: true
• debug_level: 1-3
• sleep_time: ms

3. CAN Clock Sync

CAN ID: 0x5

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👨‍💻 Interaction Examples

Reload config & enable debug

mosquitto_pub -t "translater/run" -m '{"reload": true, "debug_level": 3}'

Send control data to CAN

mosquitto_pub -t "motor/data" -m '{"rpm": 500, "torque": 2.5}'

Monitor health

mosquitto_sub -t "translater/status"

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🚀 Installation

Prerequisites

• Go 1.18+
• SocketCAN (can0)
• MQTT broker

Build

cd CanMQTT-Bridge
go mod tidy
go build -o can2mqtt cmd/can2mqtt/main.go

Bring up CAN bus

sudo ip link set can0 up type can bitrate 500000

Run

./can2mqtt

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🛠️ Development Internals

• cmd/can2mqtt/main.go – Entry point
• internal/bridge/convertfunctions.go – Translation engine
• internal/bridge/canbushandling.go – CAN handling
• internal/bridge/receivehandling.go – Worker pools

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📜 License

Distributed under the MIT License.