Lab project: a Pi Zero (the plain one, no Wi-Fi) with a BME280 that should send temperature, humidity and pressure to Hermetry over MQTT every minute. The lab has wired network ports everywhere but no Wi-Fi we’re allowed to put devices on.
While reading about HDMI 1.4 I found the HDMI Ethernet Channel (HEC), and the lab monitors and cables are all HDMI 1.4 or newer. So my idea was to get networking over the Zero’s mini-HDMI and skip buying anything. I can’t find any setting for it though, ip link only shows lo. Is there an overlay or kernel module I’m missing, or does the Zero just not do this?
Pretty sure the Pi doesn’t wire up the HEC pins at all, but I’ve never checked properly.
Curious about this too, we have HDMI runs all over our building that nobody uses.
I’m a facilities guy, not an EE, but I chased this exact idea for a lobby display last year and burned an afternoon on it. The Pi doesn’t implement HEC. On HDMI that’s pins 14 and 19, and the Pi has no Ethernet PHY behind them, so there’s nothing to switch on in software. No overlay will fix it.
What I ended up with, and what I’d try in your order:
- A micro-USB to Ethernet adapter on the Zero’s USB port (not the PWR one). ASIX AX88772 based ones work out of the box, eth0 just appears. Mine was about ten dollars.
- USB gadget mode: the Zero pretends to be a network card to a laptop over the USB cable. Add
dtoverlay=dwc2to config.txt andmodules-load=dwc2,g_etherafter rootwait in cmdline.txt. Then the laptop has to share its connection. - Swap for a Zero 2 W if Wi-Fi ever becomes allowed.
Once eth0 is up the MQTT side is the same as any other Pi, TLS on 8883 with the device token.
so with gadget mode the Zero looks like a network card to the laptop and the laptop routes for it? that means the laptop has to stay on all the time
Yep, laptop shares its connection (NAT) and has to stay on. That’s why I went with the adapter.
Found an AX88772 adapter in the lab drawer, eth0 came up on first boot, readings arriving every minute. The HEC idea is officially dead, thanks for saving me the afternoon.
- You must be logged in to reply to this topic.
Join the conversation
Sign in to ask and answer, like helpful posts and mark the reply that solved your problem. Every contribution earns points and levels.