# Nixie clock: notes for Claude

An AliExpress WiFi nixie clock (4x IN-12 + 2x IN-3 neon dots, 8x WS2812) that is being
moved from its closed stock firmware to ESP_UniClock (https://github.com/gpeter62/ESP_UniClock)
with ArduinoOTA and Home Assistant (MQTT) support.

## The device

- On the network at **10.1.1.97** (WiFi `dlink-iot`). Stock web UI on port 80, nothing else
  open: no OTA, no API, no MQTT.
- Board: RetroModding (Konstantin Repnikov) "NixieIN12v2 HV2.0", stock firmware **SV1.3**
  (©2020). ESP-12 (ESP8266, MAC 30:83:98:99:BF:DE, Espressif).
- **Powered by USB-C 5 V only** (no DC jack). Most likely the maker's "v2.0L lightweight
  5 volt version". The user says the PCB looks different from the 12 V v2 board.
- **No buttons fitted**, only the light sensor.
- Stock settings (2026-10-25): time zone +01:00, EU DST on, NTP `time.euro.apple.com`,
  brightness auto, 24 h. Stock DST might not work: check in late March.

## Stock firmware (from the flash dump)

- `firmware/stock/nixie_stock_SV1.3_full_4MB.bin` (gitignored), SHA-256
  `b069f4eb93cf1e9063a30374db4d70508211f07b0a17049bcf9ebdeda65f2985`, verified against the chip
  with `verify-flash`. Flash: 4 MB, DIO, 40 MHz.
- Arduino ESP8266 core 2.x (NONOS SDK 2.2.2-dev), built for board `ESP8266_NODEMCU`. App
  at 0x1000 (~1 MB slot), SPIFFS at 0x200000. Settings live in SPIFFS as JSON
  (`/config.json`, `/wifi.json`, `/light.json`, `/leds.json`, `/alerts.json`, `/hardware.json`).
- **Hidden pages**: `/d` = "Hardware setting" (hidden from the menu by default). It has
  checkboxes to hide/show menu items and a **Debug mode** (`dev`) checkbox. With Debug
  mode on, `/u` serves the standard ESP8266HTTPUpdateServer upload form, which is web OTA
  for `.bin`/`.bin.gz`. `/r` reboots on a plain GET; don't GET unknown paths blindly.
- No pin numbers are visible as strings; confirming the pinout needs disassembly or the
  bit-stepping test sketch.

## Pinout (from the 12 V v2 schematic, `docs/schematic_v2_12V.jpg`)

Not yet verified on this 5 V board. The stock firmware image is the same for both, which
suggests the GPIOs match.

| Function | GPIO |
|---|---|
| 74HC595 DATA / CLOCK / LATCH (OE tied to GND) | 13 / 14 / 15 (15 has 1k pull-down) |
| DS3231M RTC SDA / SCL | 4 / 5 |
| WS2812 data | 12 |
| Photoresistor (LDR, 10k to GND) | ADC (A0) |
| BTN1 / BTN2 (not fitted) | 0 / 2 |

Two chained 74HC595s make one 16-bit word, all bits active-high:
- U1 QA..QH = cathodes 0..7, U2 QA = cathode 8, QB = cathode 9 (via 2x ULN2003, shared by all tubes)
- U2 QC = P1 (neon dot 1), QD..QG = anodes A1..A4 (MMBTA42/92), QH = P2 (neon dot 2, and the decimal
  point if jumper JP2 is closed)
- The display is multiplexed: one anode on at a time. Which physical tube is A1 is unknown.

## Programming header

Header on the PCB: GND, GPIO0, RST, RXD, TXD, 3.3V. The USB-C port only supplies power.
Flashing is done with a CH340C board on **COM7** (COM3 is another device; leave it alone).
Wiring: GND-GND, adapter TXD -> clock RXD, adapter RXD -> clock TXD, adapter 3.3V not
connected (the clock is powered from its own USB-C). No auto-reset: to enter flash mode, hold
GPIO0 to GND, tap RST to GND, then release GPIO0.

- esptool is installed for the user (`python -m esptool`, v5.6.0).
- `firmware/stock/` holds the stock flash dump. **Never overwrite or delete it**; it is the
  only way back to SV1.3 (`write-flash 0 <dump>`). Dumps are gitignored because the flash
  holds the WiFi password; never commit them.

## Constraints

- The 170 V tube supply is live whenever USB-C is connected.
- Hardware is only reachable via the user: anything that needs RST/GPIO0 or looking at the
  tubes must be asked of them. Builds can be checked here, but runtime behaviour can't.
- Show the exact plan before making changes to the device (flashing, saving settings).

## Plan

1. Dump and inspect the stock firmware (version strings, pins if possible).
2. Write a test sketch that steps through the 16 shift-register bits, to verify the pinout
   and the tube order.
3. Add a 74HC595-multiplex driver + CLOCK config to ESP_UniClock, plus ArduinoOTA and
   Home Assistant controls (display on/off, brightness, LEDs); its stock MQTT only
   publishes sensors.
4. Work continues in VS Code (PlatformIO).