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
- 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 of MQTT credentials: host, port, user, pass, base topic
- Keeps a keystore for mqtts (if needed)
- Perhaps show some nice stats: connection status, packet rate, last packet, packets per type
- Perhaps run a very basic parser for e.g. CAM messages
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.
