Its-g5

Project ITS-G5
Investigating ITS-G5 signals
Status	In progress
Contact	bertrik
Last Update	2026-06-22

Introduction

This page is about investigating reception and processing of so-called C-ITS or ITS-G5 signals (802.11p) as used in the Netherlands, see also https://en.wikipedia.org/wiki/Vehicle-to-everything These signals are exchanged between passenger cars, emergency vehicles, traffic lights and other traffic-related equipment.

An ESP32-C5 development board is capable of receiving WiFi in the 5 GHz band and can receive/sniff these kinds of packets from live traffic.

Stuff to investigate:

• Source code for an ITS-G5 receiver https://github.com/pit711/v2x2map
• Crowd-sourced live map of messages received: https://opentrafficmap.org/
• Simplest source code for Arduino-based sniffer: https://git.devlol.org/jstsmthrgk/simple-its-g5-receiver-firmware
• How to contribute to opentrafficmap: https://wiki.opentrafficmap.org/?utm_source=chatgpt.com#zur_karte_beitragen

In the Netherlands, SPAT/MAPem messages from traffic lights are not transferred over wifi-p, but over UDAP. You need credentials to access that data, it is not clear if it is feasible to hobbyist to access it. Interesting project: https://github.com/idkmanLool9/Verkeerslicht

Design

The plan is:

• Use an esp32-c5 for sniffing 802.11p frames only
• Use an esp32-c3 (as an inexpensive jellybean part) for receiving sniffed frames from the esp32-c5, connect to WiFi and upload packets over MQTT
• The interface beteween the two boards is serial, this is simpler than SPI as used in other projects:
  • Only three wires required: GND, +5V and serial DATA
  • No need to desolder capacitors on SPI wires of the esp32-c5
  • A serial interface is more universal, e.g. can be connected to an arbitrary linux SBC, to run a python bridge for example
  • On the esp32-c5 use the same wires as the existing USB-UART bridge, so you can also receive packets over USB-serial
• Run a simple web server on the esp-c3:
  • Configuration page with MQTT settings: host, port, user, pass, base topic
  • Perhaps configure a keystore/certificate for secure mqtt (mqtts), if needed
  • Optional: show some nice stats: mqtt status, packet rate, last packet, packets per type
  • Optional: run a very basic parser for e.g. CAM messages

Practical:

• The serial link runs over the USB-UART chip of the esp32-c5.
• A simple command processor runs on the other UART (the emulated USB serial port)
• On the esp32-c5 side, use pins GND, 5V, GPIO25 for the ESP-ESP serial connection. These pins are right next to each other on the esp32-c5-devkitc-1. Pin GPIO25 is the pin that connects to the USB-UART chip.
• The esp32-c3 and esp32-c5 have their 5V power lines connected together. Each board derives its own internal power supplies from this 5V.
• The serial link probably doesn't have to be very high speed, start with 115200 for example. Try to use a hardware serial peripheral on both sides for this.
• Probably use the Arduino PacketSerial library on both sides for framing/deframing packets.

Hardware

I got this board, and it worked for me:

• aliexpress product page https://nl.aliexpress.com/item/1005012416463528.html
• espressif schematic https://dl.espressif.com/dl/schematics/SCH_ESP32-C5-DevkitC-1_V1.1_20240621.pdf
• espressif devkit-c page: https://docs.espressif.com/projects/esp-dev-kits/en/latest/esp32c5/esp32-c5-devkitc-1/user_guide.html

It has an onboard antenna. There are also other boards with an antenna connection, which allows using an external antenna. This may be better, I don't know yet.

Connect your USB-C cable to the "UART" port. It is connected to an actual USB-UART converter chip and always shows up, regardless of whether the ESP32 is in reset or not.

Software

See https://github.com/bertrik/its-g5-receiver

Compiling the firmware

Needs python.

Preparation:

• If you didn't have a python venv, create it:

 python -m venv .venv

• Activate the venv:

 bash source .venv/bin/activate

• Install platformio into the venv:

 python pip install platformio

Compile and upload:

 pio run -t upload

Watch packets come in:

 pio device monitor

Packets are logged as a 'hexdump'.

The can be converted for wireshark, for example:

 text2pcap -l 105 message.txt message.pcap

Then viewed in wireshark:

 wireshark message.pcap

opentraffic map interface

See https://github.com/MPW1412/openwrt-otm-bridge#wire-format-mimics-the-esp32-c5-firmware for the mqtt wire format.