html_content = """ How to Build an Embedded CAN-bus Monitor (Python + RP2040)

How to Build an Embedded CAN-bus Monitor Using Python and RP2040

This step-by-step tutorial shows you how to design an embedded CAN-bus monitor for vessel communication systems. With Python running on the RP2040 microcontroller you’ll be able to sniff, decode and display CAN frames in real time.

Prerequisites

  • Raspberry Pi Pico (RP2040)
  • CAN-bus transceiver (e.g. MCP2515)
  • Breadboard + jumper wires
  • MicroPython firmware
  • Basic Python knowledge
  • A vessel CAN network or simulator

1 · Setting Up the Hardware

Wire the MCP2515 transceiver to the Pico as follows:

  • VCC → 3.3 V
  • GND → GND
  • CAN_TX → GP4
  • CAN_RX → GP5

2 · Flash MicroPython

  1. Download the latest MicroPython .uf2.
  2. Hold the BOOTSEL button while plugging the Pico in; then drag-and-drop the .uf2 onto the new USB drive.

3 · Install Required Libraries

mpremote connect /dev/ttyACM0 fs put mcp2515.py

4 · Python Script

from machine import Pin, SPI
from mcp2515 import MCP2515

spi = SPI(0, baudrate=5_000_000, polarity=0, phase=0)
cs = Pin(17, Pin.OUT)
can = MCP2515(spi, cs)
can.reset()
can.set_baudrate(250_000)  # adjust to your bus speed
can.set_normal_mode()

print("Monitoring CAN-bus…")
try:
    while True:
        frame = can.recv()
        if frame:
            fid = frame["id"]
            data = frame["data"]
            print(f"ID 0x{fid:03X}: {data}")
except KeyboardInterrupt:
    print("Stopped monitoring.")

5 · Deploy & Test

  • Connect the Pico to the vessel’s CAN network (or a simulator).
  • Run the script via mpremote run main.py or your IDE of choice.
  • Watch the decoded frames stream in your serial console.

Tips & Next Steps

  • Use an oscilloscope to check signal integrity if frames look corrupted.
  • Match set_baudrate() to the exact bus speed (125/250/500 kbit/s, etc.).
  • Add filtering or logging for critical IDs to focus on what matters.

With this setup you have a compact, cost-effective CAN-bus monitor ready for vessel diagnostics and research.

"""