ESPHome GVRET CAN bus sniffer – wireless SavvyCAN adapter for ESP32

esphome_gvret is an ESPHome external component that turns an ESP32 into a Wi-Fi CAN bus sniffer and logger using the GVRET network protocol. It lets you monitor, log and send CAN bus frames remotely with SavvyCAN – no USB cable, no dedicated hardware like the EVTV ESP32RET or Macchina M2 needed.

Typical use cases: reverse engineering automotive / OBD-II CAN networks, debugging CANopen and industrial CAN devices, monitoring heat pumps, boilers, solar inverters, e-bikes or any other CAN-based system from your desk over Wi-Fi.

Features

• GVRET over TCP/IP (Wi-Fi) – compatible with SavvyCAN's Network Connection (default TCP port 23)
• UDP auto-discovery broadcast (port 17222) so SavvyCAN finds the device automatically on your LAN
• Multiple CAN buses – attach one or more ESPHome canbus instances (e.g. esp32_can / TWAI, MCP2515)
• Bidirectional – receive (sniff) and transmit CAN frames from SavvyCAN
• Time synchronisation with an optional ESPHome time component for accurate frame timestamps
• Runs alongside the normal ESPHome features (Home Assistant API, OTA updates, logging), so the same ESP32 can also expose CAN data as sensors
• Based on the original GVRET firmware by Collin Kidder

Hardware

Any ESP32 with a CAN transceiver works. The example uses the Olimex ESP32-EVB, which has a complete CAN bus interface (transceiver + terminal block) on board, so no extra components are required. Other options: an ESP32 dev board plus an SN65HVD230 / TJA1050 transceiver, or an MCP2515 SPI module.

Installation

Add the component to your ESPHome YAML via external_components:

external_components:
  - source: github://hencou/esphome_gvret
    components: [canbus_gvret]

Example configuration

esphome:
  name: gvret
  friendly_name: GVRET

esp32:
  board: esp32dev
  framework:
    type: arduino

external_components:
  - source: github://hencou/esphome_gvret
    components: [canbus_gvret]

api:

ota:
  - platform: esphome

logger:
  level: WARN

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

# Olimex ESP32-EVB on-board CAN interface
canbus:
  - platform: esp32_can
    id: can1
    can_id: 100
    rx_pin: GPIO35
    tx_pin: GPIO5
    bit_rate: 1000KBPS

canbus_gvret:
  can:
    - canbus_id: can1

See gvret_example.yaml for the complete file.

Configuration variables

Option	Required	Description
can	yes	List of canbus_id entries; each attached CAN bus is exposed to SavvyCAN
time_id	no	ID of an ESPHome time component used to timestamp frames

Connecting SavvyCAN

1. Flash the ESP32 with ESPHome and let it join your Wi-Fi network.
2. In SavvyCAN open Connection → Open Connection Window → Add New Device Connection.
3. Choose Network Connection and enter the IP address (or hostname) of the ESP32, port 23. Thanks to the UDP broadcast the device usually shows up automatically.
4. Click Create New Connection – CAN frames now stream into SavvyCAN in real time.

Related projects

• collin80/GVRET – original GVRET firmware (Arduino Due)
• collin80/ESP32RET – GVRET for the EVTV ESP32RET board
• collin80/SavvyCAN – cross-platform CAN bus analysis tool
• ESPHome CAN bus component

Keywords

ESPHome, ESP32, GVRET, SavvyCAN, CAN bus, CANbus sniffer, CAN logger, CAN analyzer, Wi-Fi CAN adapter, wireless CAN, TWAI, MCP2515, OBD-II, automotive, reverse engineering, Home Assistant, Olimex ESP32-EVB