Its-g5: Difference between revisions

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* Crowd-sourced live map of messages received: https://opentrafficmap.org/
* 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
* 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
* How to contribute to opentrafficmap: https://wiki.opentrafficmap.org


In the Netherlands, SPAT/MAPem messages from traffic lights are not transferred over wifi-p, but over UDAP.
In the Netherlands, SPAT/MAPem messages from traffic lights are not transferred over wifi-p, but over UDAP.
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* The serial link runs over the USB-UART chip of the esp32-c5.
* 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)
* 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.
* On the esp32-c5 side, use pins GND, 5V, UART-TX for the ESP-ESP serial connection.
* 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 esp32-c3 and esp32-c5 share their 5V and GND power lines. 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.
* The serial link doesn't have to be very high speed, 115200 for example. We use a hardware UART on both sides of the serial link.
* Probably use the Arduino [https://registry.platformio.org/libraries/bakercp/PacketSerial PacketSerial] library on both sides for framing/deframing packets.
* Use https://registry.platformio.org/libraries/thomasfredericks/MicroSlip for framing packets over the serial port.


== Hardware ==
== Hardware ==
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I got this ESP-C5-devkitC-1 board, and it worked for me:
I got this ESP-C5-devkitC-1 board, and it worked for me:
* aliexpress product page https://nl.aliexpress.com/item/1005012416463528.html
* 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 schematic https://dl.espressif.com/dl/schematics/SCH_ESP32-C5-DevkitC-1_V1.1_20240621.pdf . Actually my board is not exactly like this, the USB-UART is connected to pins GPIO11 (TX) and GPIO12 (RX), not GPIO25/GPIO24.
* espressif devkit-c page: https://docs.espressif.com/projects/esp-dev-kits/en/latest/esp32c5/esp32-c5-devkitc-1/user_guide.html
* 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.
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 ==
== Software ==
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=== Compiling the firmware ===
=== Compiling the firmware ===
Needs python.
Uses python and platformio, see the README.md in the source archive.
 
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:
Watch packets come in:
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=== opentraffic map interface ===
=== opentraffic map interface ===
See https://github.com/MPW1412/openwrt-otm-bridge#wire-format-mimics-the-esp32-c5-firmware for the mqtt wire format.
See https://github.com/MPW1412/openwrt-otm-bridge#wire-format-mimics-the-esp32-c5-firmware for the mqtt wire format.
See also https://github.com/pit711/v2x2map/blob/main/firmware/main/mqtt.c

Latest revision as of 08:13, 25 June 2026

Project ITS-G5
Investigating ITS-G5 signals
Status In progress
Contact bertrik
Last Update 2026-06-25

Introduction

wireshark analysis

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:

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, UART-TX for the ESP-ESP serial connection.
  • The esp32-c3 and esp32-c5 share their 5V and GND power lines. Each board derives its own internal power supplies from this 5V.
  • The serial link doesn't have to be very high speed, 115200 for example. We use a hardware UART on both sides of the serial link.
  • Use https://registry.platformio.org/libraries/thomasfredericks/MicroSlip for framing packets over the serial port.

Hardware

esp32-c5
esp32-c3

I got this ESP-C5-devkitC-1 board, and it worked for me:

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.

Software

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

Compiling the firmware

Uses python and platformio, see the README.md in the source archive.

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.

See also https://github.com/pit711/v2x2map/blob/main/firmware/main/mqtt.c

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