New: the AI firewall watches the whole platform and explains each incident in plain words. See how it works

Cansu Keskin

cansuk40

@cansukeskin · Joined September 2026

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Mühendislik öğrencisi · üniversite

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Translated from Türkçe by AI ·

I think it’s software. If an exception occurs in the command handler, the script may be crashing. Have you looked at the systemd log?

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Translated from Türkçe by AI ·

How will the card receive the command if the card itself is turned off? I’m curious about that.

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Translated from Türkçe by AI ·

Last term, while compiling an inventory of the Pis in the lab, I had searched for this same list.Prefixes I know: B8:27:EB for older Pis (including Pi 3), DC:A6:32, E4:5F:01, 28:CD:C1, D8:3A:DD and 2C:CF:67 for newer models. A new prefix may have been added, so look up the manufacturer in the IEEE’s public OUI list to check. As Derya said, the Ethernet and Wi-Fi MACs of the same Pi differ, but both usually share the same prefix.A more reliable approach is to have the Pi report its MAC itself: cat /sys/class/net/wlan0/address. If a script prints this somewhere on first boot, you won’t need to guess.On the Hermetry side, the import accepts a mac column and stores it in the device’s extra information. Example:

name,label,profile,mac,attr:daire
d-01,Daire 1,Ev Pi,dc:a6:32:1a:2b:3c,1
d-02,Daire 2,Ev Pi,e4:5f:01:4d:5e:6f,2

Never put a token in the file; it already rejects columns that look like secrets. The import runs a check first and then applies. The access tokens of new devices are provided in a single file, which can be downloaded only once, within 15 minutes after the import. If you miss it, get a new one from the device page with Rotate secret.Bulk importing devices

Accepted solution♥ 5

Translated from Türkçe by AI ·

I don’t think it’s power, it’s exactly the situation you described. At startup the Pi initialises GPIO0-8 with the internal pull-up (HIGH) and GPIO9-27 with pull-down (LOW). Your pins are all in the 9-27 range, so until the script runs they are LOW. The board is active-low, so LOW = relay energised = valve open. We had the same thing happen on the test rig in our lab.
There are two fixes, doing both together is the most robust:
1. Add a line to /boot/firmware/config.txt that sets the pins as outputs driven HIGH early in boot, without waiting for the script:

gpio=22-25=op,dh

This is applied at firmware stage, but a very short LOW may still occur at the very first moment of power-up. So:
2. Put a 10k pull-up resistor from each relay input to 3V3. That way the input stays HIGH even when the Pi is not driving it at all.
Also, on the Hermetry side, have the script send the valve states as telemetry such as valve1_open: 0, so after an outage you see the real state on the dashboard.

Accepted solution♥ 1

Translated from Türkçe by AI ·

Now it’s very clear, thanks Gamze Hanım. I explained to the IT team “one IP, one outbound rule” and they accepted it right away. I tried it with a Pi in the test environment during my internship, and 6 test sensors came in as child. On the first attempt I forgot to mark the gateway, and after a few messages the session closed. Turning on “This device is a gateway” in the device settings fixed it.

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