PICOKIT-47 TWO NODE MESH
September 25, 2026 ยท View on GitHub
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PICOKIT-47 TWO NODE MESH
Two-Node Mesh Relay and Authenticated Heartbeat
Lesson 47 of the Picokit Series
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Overview
The first capstone of the Picokit series. Two Pico 2 nodes share one LoRa network: one is the origin node that measures and reports, and the other is a relay and peer that hears the origin frame, authenticates it, re-seals it, and forwards it to the hub. The relay still runs the standard LED chase and authenticated heartbeat, and its heartbeat carries the running relay count so the gateway can watch the mesh grow.
What it teaches
- A two-node mesh: an origin node and a relay and peer on the same network.
- Authenticating an inbound peer envelope, then re-sealing and forwarding it.
- A heartbeat that reports the relayed count:
{"n":47,"s":<seq>,"r":<relayed>}. - The gateway side: receive, authenticate, reject, log, and display.
Hardware
| Peripheral | Pico 2 pin | Role |
|---|---|---|
| Red / Yellow / Green | GP16 / GP17 / GP18 | the chase |
| Onboard LED | GP25 | heartbeat, one blink per step |
| RYLR998 | GP8 TX / GP9 RX | mesh heartbeat and relay |
| Debug Probe | SWCLK/SWDIO/GND, GP0/GP1 | SWD and the console |
How it works
The node runs monitor_step in a loop. It advances the chase every 2 seconds
and every 5 seconds it seals {"n":47,"s":<seq>,"r":<relayed>} with the field
key and sends it over LoRa. When an inbound +RCV line carries a peer envelope,
the relay opens it with the shared key and the sender byte as associated data,
re-seals the recovered body, forwards it to the hub, and increments the relay
count. The gateway authenticates every frame and only then parses it.
Build and flash
cd firmware
cmake -S . -B build -G Ninja -DPICO_BOARD=pico2 -DPICO_PLATFORM=rp2350-arm-s
cmake --build build
openocd -f interface/cmsis-dap.cfg -f target/rp2350.cfg \
-c "program build/picokit_47_two_node_mesh.elf verify reset exit"
Watch the node
Open the console at 115200 and reset:
BOOT
I2C scan:
no devices
=== PICOKIT-47 TWO NODE MESH // LED CHASE + AUTHENTICATED HEARTBEAT ===
STEP 0 LED=RED seq=0
STEP 1 LED=YELLOW seq=1
STEP 2 LED=GREEN seq=2
RELAY from 0x002E
The gateway
cd gateway
python3 -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt
python3 listen.py --port /dev/cu.usbserial-A50285BI --hub 0001 --network 18 --db gateway.db
It prints OK node=47 rssi=... per authenticated heartbeat. The terminal
dashboard python3 tui.py --db gateway.db and the web dashboard
python3 web/app.py --db gateway.db show the same rows.
Verify
python3 .opencode/skill/embedded-c-standard/audit_c_standard.py
python3 .opencode/skill/embedded-python-standard/audit_python_standard.py
python3 .opencode/skill/iot-readme-standard/validate_readme.py
python3 .opencode/skill/iot-banner-standard/validate_banner.py
python3 scripts/run_tests.py
python3 scripts/check_coverage.py