ESP32-S3 NMEA2000 Rudder Simulator

An NMEA2000 steering control simulator for ESP32-S3 DevKitC-1 that reads rudder position from a potentiometer and broadcasts PGN 127245 (Rudder) over the CAN bus.

Overview

This firmware emulates a steering control device (Steering Control, Class 75, Function 160) on an NMEA2000 network. It reads an analog voltage from a potentiometer (ADC, 12-bit), converts it to a rudder angle, and transmits the value every 200 ms as PGN 127245.

Useful for testing NMEA2000-compatible instruments such as chartplotters, autopilots, and MFDs without a real rudder sensor.

Hardware Pinout

Component	GPIO	Purpose
POT (knob)	4	Analog input (ADC, 12-bit)
CAN TX	17	CAN bus transmit (TWAI)
CAN RX	16	CAN bus receive (TWAI)

Note: A CAN transceiver (e.g., SN65HVD230, MCP2551) is required between the ESP32-S3 TWAI pins and the NMEA2000 bus.

How It Works

1. Read: The ADC reads the potentiometer voltage (raw value 0–4095).
2. Map: The raw ADC value is linearly mapped to a rudder angle:
   • 0 → −40° (full port)
   • 2047 → 0° (amidships)
   • 4095 → +40° (full starboard)
3. Transmit: Every 200 ms a PGN 127245 (Rudder) message is sent with the current angle in radians.
4. Diagnostics (optional): Serial output at 115200 baud shows the raw ADC value, calculated angle, and the raw CAN frame in hex.

Demo

Technical Details

• MCU: ESP32-S3 (ESP32-S3-DevKitC-1)
• Framework: Arduino (via PlatformIO)
• CAN: TWAI (Two-Wire Automotive Interface), compatible with the NMEA2000 physical layer
• NMEA2000 Mode: NodeOnly (source address 22, single-node)
• Transmit PGNs: 126996 (Product Information), 126998 (Configuration Information), 127245 (Rudder)
• Transmit Period: 200 ms
• Serial Monitor: 115200 baud (diagnostics optional via #define ENABLE_SERIAL_OUTPUT)

Dependencies (PlatformIO)

Library	Version / Ref
ttlappalainen/NMEA2000-library	^4.22.0
offspring/NMEA2000_esp32 (GitHub)	main (ESP32-S3 support)
sparkfun/SparkFun BME280	^2.0.9

Dependencies are resolved automatically by PlatformIO during the first build.

Getting Started

Prerequisites

• Visual Studio Code with the PlatformIO IDE extension
• An ESP32-S3 DevKitC-1 board
• A CAN transceiver module and NMEA2000 cable (for on-bus testing)

Build & Flash

# Clone the repository
git clone https://github.com/boatdev/can-rudder-simulator.git
cd can-rudder-simulator

# Compile
pio run

# Upload to the board
pio run --target upload

# Monitor serial output (115200 baud)
pio device monitor --baud 115200

Serial Diagnostics

With #define ENABLE_SERIAL_OUTPUT enabled (default), you will see output like:

0002AFF5 0FF00 0FA0000000000000  [2047: 0.0°]
0002AFF5 0FF00 0FA0000000000000  [3072: 20.0°]

The line format is:

CAN_ID(8 hex) flags(5 hex) payload(16 hex)  [ADC_raw: angle_deg°]

Configuration

Edit src/ESP32S3_NMEA2000_device_simulator.ino to adjust:

Setting	Location
NMEA2000 source address	NMEA2000.SetMode(tNMEA2000::N2km_NodeOnly, 22)
Transmit period	tN2kSyncScheduler RudderScheduler(false, 200, 0)
Angle range	map(pot, 0, 4095, -40, 40)
CAN TX/RX pins	ESP32_CAN_TX_PIN / ESP32_CAN_RX_PIN
Enable/disable serial output	#define ENABLE_SERIAL_OUTPUT

File Structure

.
├── LICENSE                     # MIT License
├── README.md                   # This file
├── images/
│   └── photo.jpg               # Device photo
├── platformio.ini              # PlatformIO configuration
├── .gitignore                  # Files ignored by git
└── src/
    └── ESP32S3_NMEA2000_device_simulator.ino  # Main firmware

License

MIT — see LICENSE.

Acknowledgments

• Original concept by skpang
• NMEA2000-library by ttlappalainen
• NMEA2000_esp32 by offspring