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The bench leaf

v0.5 · ~$218 · an afternoon · no soldering

This guide builds the sensor node itself, the leaf, in the v0.5 build pictured here. A Grove thermistor feeds a Mayfly logger, which feeds your Pi. The Pi encrypts each reading with AES-256-GCM and hands it to the LoRa radio to queue for delivery, and a status LED blinks the whole time. This version lives in a waterproof case and runs off a USB battery bank, so it is portable enough to set out for a short field run, though without solar yet its runtime is whatever the battery holds. A leaf on its own senses, encrypts, and queues readings. It starts actually delivering them to a spreadsheet you own once you add a gateway, so this guide just gets the leaf working and proving itself, with no gateway required.

The v0.5 leaf laid out in an open tan waterproof case: a Raspberry Pi, an EnviroDIY Mayfly board, a LILYGO LoRa radio with its 915 MHz antenna, and a USB battery bank, foam-mounted.
The v0.5 leaf, with a Pi, the Mayfly, the LoRa radio, and a USB battery bank in a waterproof case. No solar yet, so it runs as long as the battery lasts.

Parts

Raspberry Pi Zero 2 W + 32 GB high-endurance microSD$32the node's computer
USB power bank (a phone charging bank)~$20powers the node into PWR IN; a 5 V wall supply also works on the bench
Micro-USB OTG adapter$3into the USB (data) port
2-port USB 2.0 hub$5bus-powered is fine on the 2.5 A supply
LILYGO TTGO LoRa32 v2.1 + 915 MHz antenna$25the radio, never power it without the antenna
SMA male → SMA female bulkhead cable (RG316, ~20 cm)$8panel-mounts the antenna
EnviroDIY Mayfly v1.1$80the sensor brain
USB-A → USB-C cable (short)$4hub → Mayfly: power + serial
Seeed Grove Temperature Sensor v1.2$7NTC thermistor, zero wiring
Grove cable$1usually ships with the sensor
LED + ~330 Ω resistor + breadboard + 2 jumpers$3status LED on GPIO 17
Waterproof case (Pelican-style) + cable gland~$30weatherproof enclosure; the antenna mounts through the wall
Total~$218

Wiring

The Pi Zero 2 W has two micro-USB ports and only one carries data:

USB power bank ──► [PWR IN]   (power pins only, no data)

[USB] ── OTG adapter ── 2-port hub ──┬── TTGO LoRa32  → /dev/rnode
                                     └── Mayfly v1.1  → /dev/mayfly

GPIO 17 ── 330 Ω ── LED ── GND       (breadboard)

Mayfly AA0/AA1 Grove socket ── Grove cable ── Grove temp sensor

⚠ Never power the radio without its antenna attached. Transmitting into nothing can kill the TTGO. With the antenna on a bulkhead through the case wall, "attached" just becomes the case's resting state.

A note on connectors. LoRa boards normally use standard SMA (the board jack has a centre socket), not RP-SMA. RP-SMA looks identical in photos but won't mate. I checked in June 2026 that these boards are standard SMA, so order plain SMA.

Build steps

  1. Flash the Mayfly

    In the Arduino IDE, add the board package EnviroDIY ATmega Boards → EnviroDIY Mayfly 1284P and the Adafruit ADS1X15 library. Open the Grove-temp sketch, read its PORT CONFIG header, and upload. With the Grove sensor in the AA0/AA1 aux-analog socket (Grove power jumper at 3.3 V), the Serial Monitor at 115200 should show a $MYC,… line every 10 s and the green LED blinking once per line. The temp_c value should be close to whatever your thermostat says.

  2. Set up the Pi

    Flash Pi OS Lite 64-bit, clone the repo, run leaf/setup.sh, and do the key and config.toml steps it prints. One of those is setting sensor = "mayfly" in /etc/mycelium-network-leaf/config.toml. Leave gateway_identity_hash blank for now. You'll set it when you build and pair a gateway. Then reboot.

  3. Plug the chain together

    Wire it per the topology above, then check that both serial devices show up by running ls -la /dev/rnode /dev/mayfly. (udev pins each device by chip, so hub port order never matters.)

  4. Start and watch

    Run sudo systemctl start rnsd leaf-node, then journalctl -u leaf-node -f. With no gateway yet, you should see the leaf sampling real readings and queuing them, with lines like sampled: temp_c=21.340 (queue depth 1) and the queue depth climbing. The LED slow-blinks discovering while it listens for a gateway to announce itself. That is the leaf working on its own.

Prove it's real

Pinch the thermistor between two fingers for a minute. In the journal, the sampled temp_c should climb a few degrees. That is the whole sense-and-encrypt path measuring an actual thing. Those queued readings start landing in a spreadsheet you own once you add a gateway.

The same node sealed in its tan waterproof case, with the 915 MHz antenna mounted through the top of the case on a bulkhead.
Buttoned up, the antenna passes through the case wall on a bulkhead, and the whole node runs off the battery bank inside. Portable enough to set out for a short field run, though without solar it lasts only as long as the bank.

Troubleshooting

What this proves, and what it doesn't

It proves the full encrypted pipeline end to end, the sensor-protocol contract across two independent implementations, named multi-parameter readings, and the whole reliability stack running under a real sensor.

It doesn't prove a season of real weather, solar power (this runs off a battery bank, so its uptime is just the battery), SDI-12, or a submersible water-temp probe. The waterproof case keeps the rain off, but the full field build, with solar, a real sonde, and a season of proof, is still ahead.

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