M5Stack NMEA2000 Display for CAN BUS

This repository shows how to use the M5Stack as NMEA 2000 Display and WiFi Gateway. The M5Stack is receiving the data directly from the CAN bus.

The project requires the NMEA2000, NMEA2000_esp32 and NMEA0183 libraries from Timo Lappalainen: https://github.com/ttlappalainen

For the M5Stack the board software and library have to be installed: https://docs.m5stack.com/#/en/arduino/arduino_development

The M5Stack has only a limited number of GPIO pins available. The initial version used GPIO 2 (CAN TX) and GPIO 5 (CAN RX). That led to problems with the NMEA2000 bus due to signals on both lines during boot and flash time.

The new version (since version 0.2) is using GPIO 17 (TX) and GPIO 16 (RX) to avoid the problem.

The M5Stack can also work as WiFi Gateway to send NMEA 0183 messsages (TCP port 2222) via WiFi. Just set ENABLE_WIFI to "1" to enable. Change SSID/password accordingly.

The only external hardware is the CAN bus transceiver (Waveshare SN65HVD230). It is connected to 3,3 V, GND, CAN TX (GPIO 17) CAN RX (GPIO 16).

With the left two buttrons you can flip through the pages (5 pages currently) with differnt NMEA 2000 data. The right button is changing the backlight of the LCD.

Remove the 120 ohm resistor from the transceiver

For unknown reasons, many CAN bus transceivers for the ESP32 have a 120 Ohm resistor built into them. The resistor does not belong to the devices at the ends of the stub lines, but to the ends of the backbone cable.

Whether the transceiver contains a 120 ohm resistor can be determined either by looking at the circuit diagram or by measuring with the multimeter.

A knife tip is suitable for removing the SMD resistor. Use it to scratch or pry off the resistance. With the transceiver shown here, place the tip of the knife in front of the resistor (between the chip and the resistor) and support the knife against the chip. Then lever the tip against the resistance and use it to scratch / loosen / break the resistance. Whichever happens first.

It then looks like the picture. Then measure to be on the safe side. Without a 120 ohm resistor, the multimeter shows approx. 75 kOhm.

Updates:

• 02.03.2021 - Version 0.3: Added changed source address check.
• 01.03.2021 - Version 0.2: Changed CAN bus GPIOs.
• 23:11.2019 - Version 0.1: Initial version.