1602A Sniffer

Sniff a 1602A style LCD interface from a Geiger counter, mirror the screen text, and turn it into real data.

This project is a demonstrator: take a device that only speaks via an HD44780 style LCD header and make it stream useful numbers. Think Fallout, Pip Boy vibes, but real sensor data.

Target use case: A common handheld Geiger counter that drives a 16x2 LCD and does not provide serial output. Example listing: https://www.ebay.com/itm/357934090548

What it does:

• Passive sniff of the LCD bus, no LCD required
• Mirrors the 16x2 text over USB serial
• Extracts values from display labels
  • R: rate in uSv per hour
  • A: average in uSv per hour
• Computes derived metrics
  • Peak rate
  • Running dose in uSv
  • EMA smoothing, 1 minute and 10 minute
  • Approx rad per hour and rad per second
• Alarm states for demos
  • FOUND, sustained rise above baseline
  • FLIGHT, sustained elevated band
  • DANGER, absolute threshold
  • UNHEALTHY, absolute threshold

Why this exists:

• This shows how far you can go without vendor firmware, without UART pins, without reverse engineering the MCU.
• It is a clean stepping stone to ESP32, Meshtastic, and a web UI.

Hardware

This project now supports two practical wiring targets:

• Arduino Uno as the original 5V reference build
• Arduino Micro as the working PlatformIO port used for the traced Geiger harness

Connections are documented in: docs/WIRING.md

Working Arduino Micro mapping used by the current PlatformIO firmware:

• RS -> D2
• RW -> D4
• E -> D12
• D0 -> D11
• D1 -> D10
• D2 -> D9
• D3 -> D8
• D4 -> D7
• D5 -> D6
• D6 -> D5
• D7 -> D3

Notes:

• This matches the traced harness where the Arduino-side D3 and D4 wires are swapped.
• On this Micro wiring, the byte bus is captured directly and the firmware infers command vs data from the HD44780 byte stream, because the traced control-line levels are not as clean as the byte data.

Output

Example lines:

• LCD|R:00.16 usv/h 1|A:00.18 usv/h o|
• rate_usvph=0.16 avg_usvph=0.18 ema1m_usvph=0.15 ema10m_usvph=0.12 peak_usvph=0.26 dose_uSv=0.004 rate_radph=0.00001600 rate_rads=0.0000000044 dose_rad=0.00000040 alarm=OK

More examples in: docs/SERIAL_EXAMPLES.md

Units and rad note

The device appears to print uSv per hour. The rad conversions here are a demonstration only.

uSv is equivalent dose. rad is absorbed dose. Converting between them depends on radiation type and quality factor. This code assumes gamma or x ray like conditions where quality factor is near 1, so:

• 1 Sv is treated as 1 Gy
• 1 Gy equals 100 rad

If you want strict correctness across radiation types, keep everything in Sv units or calibrate for your tube and spectrum.

Next steps

• Port to ESP32 S3 and add WiFi, web UI, logging
• Add Meshtastic telemetry packets
• Add physical UI, servo needle gauge, buttons, RGBW indicator

Topics to use on GitHub

Suggested repo topics: 1602a, hd44780, lcd, sniffer, reverseengineering, geigercounter, radiation, doserate, esp32, meshtastic, fallout, pipboy, retrocomputing, iot

Repo layout

• arduino/1602A_Sniffer/ – Arduino Uno sketch for the original reference wiring.
• docs/ – Wiring and serial-output examples you can read before wiring up the counter.
• PlatformIO scaffolding (platformio.ini, src/main.cpp, include/, lib/, test/) now includes the working Arduino Micro implementation.

Building locally

1. For the original Uno path, open arduino/1602A_Sniffer/1602A_Sniffer.ino in the Arduino IDE and wire the board per docs/WIRING.md.
2. For the working Micro path, open the repo in PlatformIO and build the default micro environment.
3. If your upload port is not auto-detected, pass it explicitly, for example pio run -e micro -t upload --upload-port COM20.
4. Open a 115200 baud monitor and watch the serial stream mirror the display and report metrics; the sniffer is passive so no LCD is connected.

License

MIT