Me again. Our lab has 6 freezers and incubators on Hermetry with alarm rules and they work, but alerts go to the bell and nobody looks at the screen while wearing gloves. The PI asked if a speaker could just say “Freezer 3 temperature high” in the room.
I have a spare Pi 4 and a USB speaker. Offline text to speech works (I tested piper and espeak-ng, piper sounds much nicer). The part I don’t get is how the Pi finds out about a new alarm. I set up a webhook in Hermetry pointing at the Pi and nothing ever arrives. The Pi is on the university network behind NAT, no public address. Is a webhook the wrong tool?
Could you have it announce by e-mail somehow? Like read the inbox?
Webhooks need an HTTPS URL Hermetry can reach from outside, so behind NAT they’ll never land. You’d need a tunnel or a reverse proxy, and uni IT will probably say no.
Or turn it around and have the Pi ask. Pull beats push when the receiver is behind NAT.
following, I want this for my intercom thing too lol
We do this on our plant floor, a Pi with a horn speaker reads critical alarms over the noise. Ciaran’s right, poll the Alarms API.
Ask your admin for an API key with only the alarm read permission (reading alarms is a User-level permission by default) and an IP allowlist for the uni’s address. Then:
import requests, subprocess, time
H = {"Authorization": f"Bearer {API_KEY}"}
URL = f"https://{HOST}/tenant/{TENANT}/api/iot/alarms"
seen = set()
while True:
r = requests.get(URL, headers=H, params={"status": "OPEN", "severity": "CRITICAL,MAJOR",
"sort": "opened:desc", "pageSize": 20}, timeout=10)
for a in r.json()["items"]:
if a["alarmId"] not in seen:
seen.add(a["alarmId"])
subprocess.run(["sh", "-c", f'echo "{a["deviceName"]}: {a["title"]}" | piper --model en_GB-alan-medium.onnx --output-raw | aplay -r 22050 -f S16_LE'])
time.sleep(15)
Status OPEN means acknowledged alarms stop being read, which people like: ack it in the app and the room goes quiet. Give your alarm rules readable titles because that’s what gets spoken, e.g. “{{device.name}} temperature {{value}}”. Fifteen seconds is a polite poll rate, stay well under the API limits. If you ever do get a public endpoint, the alarm.created webhook would replace the polling: Webhooks.
Got it running yesterday, everyone in the lab loves it. Had to ask IT nothing, which was a win. Only thing: I first used status=active and it kept repeating acknowledged alarms after a restart because my seen-set was empty, switched to OPEN like you wrote. Also had to change device names from “frz-03” to “freezer three” because piper read it as “frz”.
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