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mangavalkandClaude Opus 5.5 8efa810e4e Map stock firmware GPIO use from disassembly 
Disassembled the SV1.3 app image and confirmed the shift-register
(HSPI 13/14 + latch 15), WS2812 (12), LDR (A0) and button pins, the
16-bit bit map and the tube order. The stock firmware has no I2C code
and drives a DFPlayer on UART0. Adds the ELF/xref helper tools.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-25 20:42:56 +01:00

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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), checked against the stock firmware by disassembly (docs/stock-firmware-pins.md, tools in tools/). "Binary" = confirmed in the stock SV1.3 code; it has not yet been tested on the hardware.

Function GPIO Source
74HC595 DATA / CLOCK (OE tied to GND) 13 / 14 = HSPI MOSI / SCK (hardware SPI, MSB first) Binary
74HC595 LATCH 15, plain digitalWrite (has 1k pull-down) Binary
WS2812 data 12 (NeoPixel bit-bang, GRB 800 kHz; stock assumes 12 LEDs, 8 fitted) Binary
Photoresistor (LDR, 10k to GND) ADC (A0) Binary
BTN1 / BTN2 (not fitted) 0 / 2, INPUT_PULLUP. Stock: GPIO0 is a button, GPIO2 a motion/presence input that wakes the display Binary
DFPlayer Mini (stock feature) UART0: GPIO1 TX / GPIO3 RX, 9600 Bd Binary
DS3231M RTC SDA / SCL 4 / 5. Stock firmware has no I2C code (NTP only); if fitted, unknown Schematic only

Two chained 74HC595s make one 16-bit word, all bits active-high (confirmed from the binary; the high byte is sent first and goes to U2):

  • U1 QA..QH = cathodes 0..7 (bits 0..7), U2 QA = cathode 8 (bit 8), QB = cathode 9 (bit 9) (via 2x ULN2003, shared by all tubes)
  • U2 QC = P1 (neon dot 1, bit 10), QD..QG = anodes A1..A4 (bits 11..14, MMBTA42/92), QH = P2 (bit 15; neon dot 2, and the decimal point if jumper JP2 is closed)
  • The display is multiplexed: one anode on at a time. A1 = leftmost tube (hour tens), A4 = rightmost (minute ones), from the stock digit order. Stock lights P1/P2 in only one multiplex slot.

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).
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