Table of Contents
FAQ
What does the QR Code mean on the back side of the case?
If you scan the QR code with a mobile phone, you will be directed to the “Node Admin page” of this device. URL https://opentrafficmap.org/service/?nodeId=nodeXXX
ATTENTION: Please change the “User Password” to protect your node settings!
More info can be found here: Node Registration
What do the LEDs mean?
| Label | Color | Meaning |
|---|---|---|
| SYS | red / white | |
| RCV | orange | |
| ETH | green | |
| MQT | blue | |
| PKT | purple |
Does it matter which USB-C port powers it?
No, it doesn't matter which USB port you use to power the board.
More info can be found here: Getting Started
My phone won't do USB tethering — why?
Common causes:
- The cable is a charge-only cable with no data wires → use a proper data cable.
- USB tethering is not enabled on the phone (Settings → Hotspot/Tethering).
- The node's port is a power-only port (see above).
- Missing driver / USB role (host vs. device) — some nodes must be configured as USB host.
Is there a data buffer when offline?
No. At the moment (Firmware 0.5.1) there is no support for local data logging to the SD-card.
More info can be found here: MQTT Server
Which antennas can I use?
The node with the case has an integrated antenna. (comes with the ESP32)
More info can be found here: External Antennas
Why is my node so hot?
Typical temperature is about 55°C.
Possible reasons:
- Status LEDs at full power (set via Admin Node Portal > Set brightness (0 = off, 255 = maximum)
- Direct sunlight on outdoor installations.
In direct sunlight in summer season more than 83°C were seen. 
More info can be found here: Reception & Placement
Why is reception poor despite good height?
- interference of a 5GHz WLAN Access Point nearby → separate the devices or deactivate 5GHz (ESP32 only uses 2.4GHz)
- indoor usage (Tinted windows also reflect waves) → mount outdoor
More info can be found here: Reception & Placement
How do I monitor my node in Home Assistant?
Common approaches:
- MQTT: the node publishes telemetry to a broker, HA reads it via the MQTT integration.
From there you can build sensors, automations, and dashboards in HA.
More info can be found here: Home Assistant
PoE vs USB powered / jumper settings?
To switch the mode, the blue jumper must be removed and placed on the correct pins.
| Power source | Jumper position | Notes |
|---|---|---|
| Active PoE (IEEE 802.3af/at) | 802.3af | Power via LAN cable from a standards-compliant PoE switch or injector. The board signals itself as a PD; the port is only switched on after successful negotiation/classification. |
| Passive PoE | Passive | Power via LAN cable from a passive injector supplying the rated DC voltage directly – no negotiation, no classification. Does not work on an 802.3af switch (the port stays off). |
| USB | irrelevant | Power via the USB port (either one). Independent of the jumper position. Do not supply USB and PoE at the same time! |
More info can be found here: Getting Started
Do I need surge protection for an outdoor node?
If the receiver is mounted outside and the LAN cable runs to a switch indoors: yes, recommended. See surge_protection – one inline surge protector per outdoor run, and it must be grounded.
Does the node support WIFI?
No. The Espressif ESP32 C5 is used to receive the C-ITS signals only. So you have to use the LAN port.
More info can be found here: Getting Started
How to view the raw data (MQTT packets) the node sends to the server?
To view (“subscribe” in MQTT language) you can use the MQTT client of your choice.
Here's a (incomplete) list of clients:
| OS | MQTT Client | Homepage |
|---|---|---|
| Linux | MQTTX | https://mqttx.app |
| Linux | MQTT Explorer | https://mqtt-explorer.com |
| Linux | MQTT Viewer | https://mqttviewer.app |
| Windows | MQTTX | https://mqttx.app |
| Windows | MQTT Explorer | https://mqtt-explorer.com |
| Windows | MQTT.fx | https://mqttfx.jensd.de |
| Mac | MQTTX | https://mqttx.app |
| Mac | MQTT Explorer | https://mqtt-explorer.com |
| Mac | MQTT Viewer | https://mqttviewer.app |
More info can be found here: MQTT Server
How does OpenTrafficMap know the location of my node?
The location is unknown until you specify it in the Node Admin Portal under “Set coordinates on map”.
More info can be found here: Node Registration
Why is my node (not) visible on the map?
Your node will only appear on the map if you enable the “[X] Show on map” option in the node admin portal.
More info can be found here: Node Registration