aisha.maker
@aisha_r58 · Joined October 2025
Maker · home automation · Brisbane
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hciuart failing on a Pi 3 that also does Modbus on the serial header: I’d bet whoever set up the Modbus put dtoverlay=pi3-disable-bt in /boot/config.txt to get the good UART on GPIO14/15. That overlay switches the BT chip off completely, so hciuart has nothing to talk to.
You can have both. On Stretch use the other overlay, which gives BT the mini UART and keeps the PL011 on the header:
# /boot/config.txt
#dtoverlay=pi3-disable-bt
dtoverlay=pi3-miniuart-bt
core_freq=250core_freq=250 keeps the mini UART’s clock stable, BT gets flaky without it. Also make sure console=serial0,115200 is not in cmdline.txt. Reboot, then sudo systemctl restart hciuart and hciconfig should show hci0.
Your Modbus side keeps /dev/ttyAMA0, so the chiller code shouldn’t notice.
Some of those machines have an MDB bus inside that reports vends properly, might be worth a look before you drill more holes.
Kevin A’s point matters, because it decides which baud the HC-05 has to use: old bootloader is 57600, the new Optiboot one is 115200. The HC-05 has to be set to that same speed with AT commands first.
Did almost exactly this for a gate camera at my uncle’s farm.
Cable: 100 m is per segment. Options, cheapest first: a PoE extender halfway (needs a spot to mount it, some are powered by the PoE itself), a small outdoor switch halfway with power, or two fibre media converters with a fibre run, which also kills any lightning worries between buildings. Kevin’s Wi-Fi idea works as a point-to-point bridge with two directional units, not with the camera’s own Wi-Fi.
Hermetry side, the refusal is expected. The cloud connects to the camera, so it has to be reachable at a public host name or IP, or through a Hermetry Edge on the site network (the platform then gets to it over Edge’s encrypted connection, no port forward). A private address like 192.168.x on its own is refused. Without an Edge box: forward the camera’s HTTP and RTSP ports on your router, allow only the platform’s addresses through the firewall, and add it with a view-only camera user, not admin. Then Devices > New device > Camera or recorder, test the connection, and put it on the board.
Check the stream codec. It’s H.264 only, no audio. A lot of new cameras default to H.265 and you’ll get a black tile. Live view stores nothing, it pulls video only while someone watches, and each minute somebody watches counts toward the plan’s camera minutes. If you put it on a wall screen all day that adds up. Limits on Camera limits and privacy.
Video needs Wi-Fi-class bandwidth, and 2.4 GHz through that much concrete dies fast.
Could you just add a second resistor in series in the loop and read the voltage across it with the ESP? That’s what I did with a pressure sensor at home.
Not a lawyer, but I went through this with a test lab for a BLE product. The modular grant covers the radio as long as you stay inside it: same antenna type and gain, no changes to output power, frequencies or modulation, and the module’s FCC ID shown on your label (“Contains FCC ID …”). Updating your own application code doesn’t touch that. The host product still needs its own unintentional-emitter check (Part 15B), once, not per update. Ask your lab to put that in writing for your file, it’s a short email for them.
Where you could break the grant is if an update ever lets the radio config change, so lock that: the app should have no command or setting that changes bands or power.
On the Hermetry side, what I’d set up before the first real rollout:
- Register your signing public key under Firmware > Signing keys and keep “Allow unsigned images” off on the tracker profile. Only an owner can add keys, and the device must refuse an image whose signature doesn’t verify, so build that check into your bootloader.
- Fill in Hardware models on each upload, so a rev B image never goes to rev A boards.
- Use Send in waves on the profile assignment, start with your own 10 test trackers.
- Leave “Allow updates over LTE” off until you know the image size and your data plan, otherwise each tracker downloads it on cellular the moment it’s assigned.
- Report
current_fw_versionafter every connect. Hermetry only marks an update done when the new version actually shows up, and flags it if the old one comes back.
All on Firmware updates (OTA).
Did you enable 1-Wire in raspi-config? And the resistor is not optional, 4.7k between data and power.
Byte order it was. Swapped them and the soil value sits at 1.62 V, steady. I added soil.raw next to soil.v like Keisha said, and the battery on AIN1 reads 12.7 V after the divider maths. Also understand now what that argument is, thanks Aoife.
Your single quotes stop $ok from expanding. That literal text isn’t valid JSON, so it gets stored as raw.