JMRI and Arduino Integration

Connect Arduino sensors and outputs to JMRI for computer-controlled layout automation.

Integration Methods

1. CMRI Protocol (Recommended)

• Well-supported in JMRI
• Multiple node addresses
• Reliable communication

2. Direct Serial

• Custom commands
• More flexible but requires scripting

CMRI Setup

Arduino Library

#include

CMRI cmri(0, 24, 24); // Node 0, 24 inputs, 24 outputs

void setup() {

Serial.begin(9600, SERIAL_8N2);

// Set up your pins...

}

void loop() {

cmri.process();

// Read sensors

cmri.set_bit(0, digitalRead(2)); // Sensor on pin 2

// Control outputs

digitalWrite(3, cmri.get_bit(0)); // Output on pin 3

}

JMRI Configuration

1. Open Preferences → Connections
2. Add new connection type: C/MRI
3. Select your serial port
4. Configure node address (must match Arduino)

Practical Applications

Block Detection

• Connect current sensors to Arduino inputs
• Report occupancy to JMRI
• Use in turnout control automation

Turnout Control

• JMRI sends commands
• Arduino controls servo motors
• Report back position

Signal Control

• JMRI calculates aspects
• Arduino drives LEDs
• Supports complex signaling rules

Testing the Connection

1. Open JMRI Sensor Table
2. Add sensor at configured address
3. Trigger Arduino input
4. Watch sensor state change in JMRI

Tips

• Use consistent node addressing
• Document your pin assignments
• Test each sensor individually
• Add status LEDs for debugging