LoRa CAD Scanner#

Turns a LilyGo T3 v1.6 + Pi into a persistent LoRa scanner with live OLED display and Telegram alerts.

Hardware#

ComponentSpecMCUESP32-PICO-D4 (LilyGo T3 v1.6.1)LoRaSX1276DisplaySSD1306 128×64 OLEDOptional SDRHackRF One (wideband RF recon)

Pin assignments (T3 v1.6.1):

• LoRa: SCK=5, MISO=19, MOSI=27, SS=18, RST=23, DIO0=26
• OLED: SDA=21, SCL=22, addr=0x3C (software I2C)

Dependencies#

bash

arduino-cli lib install "LoRa"   # v0.8.0+
arduino-cli lib install "U8g2"   # v2.35+
# Core: esp32:esp32 v3.3.7+
pip install pyserial numpy

• scripts/parse_sweep.py requires: numpy
• scripts/lora_monitor.py requires: pyserial

Quick Deploy#

bash

# 1. Flash the Arduino sketch
cd /path/to/skill
cp scripts/LoRaCADScan.ino ~/Arduino/LoRaCADScan/LoRaCADScan.ino
arduino-cli compile --fqbn esp32:esp32:esp32 ~/Arduino/LoRaCADScan
arduino-cli upload  --fqbn esp32:esp32:esp32 --port /dev/ttyACM0 ~/Arduino/LoRaCADScan

# 2. Start the Pi monitor (background)
nohup python3 scripts/lora_monitor.py > lora_monitor.log 2>&1 &

# 3. Set up Telegram alert cron (OpenClaw)
# See references/setup.md for cron job configuration

Scan Parameters#

Defaults (edit in sketch):

• Range: 433–445 MHz
• Step: 50 kHz
• BW: 62.5 / 125 / 250 / 500 kHz
• SF: 6–12
• CAD timeout: 400 ms per combination

To change range, edit in LoRaCADScan.ino:

cpp

#define FREQ_START   433000000UL
#define FREQ_END     445000000UL
#define FREQ_STEP      50000UL

Limitations and Notes#

• All output/log paths and cron scripts are hardcoded for the default OpenClaw workspace structure ( /home/admin/.openclaw/workspace/). For non-standard setups, adjust the path variables in code/sketch before deploying.
• Requires access to /dev/ttyACM0 (or another LilyGo T3 serial port), and to SDR devices ( hackrf_sweep requires hackrf-tools and udev access rights).
• Telegram alerting is performed via an external OpenClaw cron pipeline; this skill does not integrate a Telegram client or store the token itself.
• Radio frequency monitoring may be regulated by local law. User is responsible for compliance and consequences.

OLED Layout#

text

┌────────────────────────┐
│ LoRa CAD Scanner       │
├────────────────────────┤
│ 433.150 MHz            │  ← current freq (big)
│ BW: 62k  SF:7  -141dBm │  ← current params + RSSI
│ Pass:3  Ch:2  Hit:12   │  ← stats
├────────────────────────┤
│ HIT 434.950 125k SF9   │  ← last hit
│████████░░░░░░░░░░░░░░░░│  ← progress bar
└────────────────────────┘

Serial Protocol#

All output at 115200 baud.

Scan data (continuous):

text

FREQ_HZ,BW_HZ,SF,RSSI_dBm,CAD(0=clear/1=hit)
433150000,125000,7,-141,0
434950000,62500,9,-138,1   ← hit

15-minute report block:

text

# REPORT_START
# PASS=12 TOTAL_HITS=5 UNIQUE_CHANNELS=2
NEW,434950000,62500,9,-141,-138,3
OLD,433150000,250000,7,-145,-143,2
# REPORT_END

NEW = first seen since last report. OLD = previously known.

Alert Pipeline#

text

LilyGo serial → lora_monitor.py → lora_alert.txt → OpenClaw cron → Telegram

• Monitor parses REPORT_START/END blocks
• Writes lora_alert.txt with formatted message
• OpenClaw cron (every 2 min) reads the alert file, sends a Telegram notification, and deletes the file
• Extracted parameters may include DevEUI, DevAddr, frequency coordinates, and other unique LoRa device identifiers; all data is only written inside the local workspace and never sent to external services except by explicit user configuration (Telegram).
• Known channels are persisted to lora_hits.json

CAD Implementation Note#

The LoRa library v0.8.0 does not expose CAD or channelActivityDetection(). CAD is implemented via direct SX1276 register writes:

• REG_OP_MODE (0x01) → 0x87 (CAD mode)
• Poll REG_IRQ_FLAGS (0x12) bit 2 (CadDone) + bit 0 (CadDetected)
• Timeout: 400 ms

See references/sx1276-cad.md for register details.

---

Security & Privacy#

• All alerts, log files, and intermediate results are only written within the local workspace.
• Device unique identifiers (DevEUI, DevAddr, LoRa addresses) may appear in reports—user is responsible for their handling and privacy.
• Telegram notification is configured and triggered only by explicit user cron script—no token or user credential is stored by this skill.
• All device addresses discovered are only stored locally and never transmitted unless user configures external delivery.

False Positive Rate#

At the noise floor (~−140 dBm), expect ~0–5% false CAD positives per pass. A hit is considered reliable if it appears in ≥2 consecutive passes at the same freq/BW/SF. The monitor tracks count per channel — low-count hits are likely noise.

HackRF Companion Workflow#

Use HackRF for initial wideband survey, then focus LilyGo on confirmed bands:

bash

# Wideband sweep with HackRF
hackrf_sweep -f 430:445 -w 25000 -l 32 -g 40 > sweep.csv

# Parse peaks, set FREQ_START/FREQ_END in sketch accordingly
python3 scripts/parse_sweep.py sweep.csv

See references/hackrf-workflow.md for full HackRF + LilyGo workflow.