Update docs and firmware for ESPHome bridge migration

- Replace gauge.py (MicroPython) references with gaugecontroller.yaml (ESPHome)
- Update CLAUDE.md and README.md to document ESPHome-native API integration
- Update LED wiring docs for separate main/indicator strips (D22/D36)
- Refactor Arduino firmware to drive two WS2812 strips independently
- Add per-gauge physical offset caching for main and indicator LEDs
- Frame-limit breathe effect (16ms) to reduce unnecessary strip refreshes

CLAUDE.md

@@ -0,0 +1,111 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build & Upload
+
+Main firmware lives in `Gaugecontroller/Gaugecontroller.ino`. Requires the **FastLED** library (`arduino-cli lib install FastLED`). Use the Arduino IDE or `arduino-cli`:
+
+The ESP32 bridge runs ESPHome; the config is in `gaugecontroller.yaml`.
+
+```bash
+# Compile (replace board/port as needed)
+arduino-cli compile --fqbn arduino:avr:mega Gaugecontroller
+
+# Upload
+arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:avr:mega Gaugecontroller
+```
+
+Current default serial setup: `CMD_PORT` and `DEBUG_PORT` both point to `Serial1` at 38400 baud.
+
+## Switching serial ports (debug → production)
+
+Two `#define`s at the top of `Gaugecontroller.ino` control where commands and debug output go:
+
+```cpp
+#define CMD_PORT   Serial1  // command channel (host sends SET, HOME, etc.)
+#define DEBUG_PORT Serial1  // diagnostic prints (homing, boot messages)
+```
+
+**Current default:** both point to `Serial1`, so command and debug traffic share Mega pins TX1=18 / RX1=19 at 38400 baud.
+
+**USB-only debug setup:** point both defines back at `Serial` if you want to talk to the sketch over the Arduino USB port instead:
+
+```cpp
+#define CMD_PORT   Serial
+#define DEBUG_PORT Serial
+```
+
+At that point the matching `begin()` call in `setup()` also needs to use the same baud rate you expect on the host side.
+
+**Split command/debug ports:** if `CMD_PORT` and `DEBUG_PORT` do not point to the same serial port, `setup()` must initialise both. Right now it only calls:
+
+```cpp
+DEBUG_PORT.begin(38400);
+```
+
+If you split them, add a second `CMD_PORT.begin(...)` call.
+
+Arduino Mega hardware UARTs for reference:
+
+| Port    | TX pin | RX pin |
+|---------|--------|--------|
+| Serial1 | 18     | 19     |
+| Serial2 | 16     | 17     |
+| Serial3 | 14     | 15     |
+
+## Architecture
+
+The sketch controls `GAUGE_COUNT` stepper-motor gauges using a trapezoidal velocity profile and a simple text serial protocol.
+
+### Key data structures
+
+- `GaugePins` — hardware pin mapping per gauge (dir, step, enable, active-high/low polarity flags, `ledOrder` string). Declared `constexpr` so `TOTAL_LEDS` can be computed from it at compile time. Configured in the `gaugePins[]` array at the top.
+- `Gauge` — per-gauge runtime state: position, target, velocity, accel, homing state machine, sweep mode.
+
+### Motion control (`updateGauge`)
+
+Each call to `updateGauge(id)` in `loop()` computes `dt` since last call and updates velocity using a braking-distance check to produce smooth trapezoidal motion. Steps are accumulated as floating-point and emitted via `doStep` when the accumulator crosses ±1.
+
+### Homing sequence (`updateHoming`)
+
+State machine: `HS_START → HS_BACKING → HS_SETTLE → HS_DONE → HS_IDLE`.  
+Backs up `homingBackoffSteps` at `homingSpeed`, waits 100 ms settle, then declares `currentPos = 0`. No physical end-stop is used; homing is purely time/step-count based.
+
+### Sweep mode
+
+When `sweepEnabled`, `updateSweepTarget` bounces `targetPos` between `minPos` and `maxPos` autonomously.
+
+### LED strip
+
+Two LED strips are driven: main backlight/status LEDs on `LED_DATA_PIN` (currently 22) and dial indicator LEDs on `INDICATOR_LED_DATA_PIN` (currently 36). The serial protocol still exposes one logical per-gauge LED segment: `0-2` backlight, `3-4` indicators, `5-6` status. `gaugePins[i].ledOrder` is a per-LED type string (one char per LED, `'G'` = GRB-ordered, `'R'` = RGB-ordered) and its length defines the logical LED count. `TOTAL_LEDS`, `TOTAL_MAIN_LEDS`, and `TOTAL_INDICATOR_LEDS` are computed at compile time. Per-gauge logical and physical offsets are cached in `setup()`. LED writes dirty only their physical strip, and the loop flushes each FastLED controller independently with `showLeds()`.
+
+### Serial command protocol
+
+Commands arrive as newline-terminated ASCII lines. Each `parse*` function in `processLine` handles one command family:
+
+| Command | Syntax | Effect |
+|---|---|---|
+| `SET` | `SET <id> <pos>` | Move gauge to absolute step position |
+| `SPEED` | `SPEED <id> <steps/s>` | Set max speed |
+| `ACCEL` | `ACCEL <id> <steps/s²>` | Set acceleration |
+| `ENABLE` | `ENABLE <id> <0\|1>` | Enable/disable driver output |
+| `ZERO` | `ZERO <id>` | Mark current position as home without moving |
+| `HOME` | `HOME <id>` / `HOMEALL` | Run homing sequence |
+| `SWEEP` | `SWEEP <id> <accel> <speed>` | Start sweep (0/0 stops) |
+| `POS?` | `POS?` | Query all gauges: `POS <id> <cur> <tgt> <homed> <homingState> <sweep>` |
+| `LED` | `LED <id> <idx> <r> <g> <b>` | Set one LED (0-based index within gauge segment) to RGB colour (0–255 each); `<idx>` may be a range `N-M` to set LEDs N through M in one command; also stops any active effect on those LEDs |
+| `LED?` | `LED?` | Query all LEDs: one `LED <id> <idx> <r> <g> <b>` line per LED, then `OK` |
+| `BLINK` | `BLINK <id> <idx> <on_ms> <off_ms> <r> <g> <b>` | Blink LED(s) at given colour; `<idx>` may be a range `N-M`; `on_ms`/`off_ms` both 0 stops blinking. 4-arg form (no colour) uses current LED colour |
+| `BREATHE` | `BREATHE <id> <idx> <period_ms> <r> <g> <b>` | Smooth triangle-wave fade between black and the given colour; `<idx>` may be a range `N-M` |
+| `DFLASH` | `DFLASH <id> <idx> <r> <g> <b>` | Two quick flashes (100 ms on/off each) followed by a 700 ms pause, then repeats; `<idx>` may be a range `N-M` |
+| `PING` | `PING` | Responds `PONG` |
+
+All commands reply `OK` or `ERR BAD_ID` / `ERR BAD_CMD` etc.
+
+### Adding gauges
+
+1. Increment `GAUGE_COUNT`.
+2. Add a `constexpr GaugePins` entry to `gaugePins[]` (including the `ledOrder` string — one char per LED, `'G'` for GRB or `'R'` for RGB).
+3. Tune `maxPos` and `homingBackoffSteps` in the corresponding `Gauge` default or at runtime.
+4. `TOTAL_LEDS`, `gaugeLedOffset[]`, and `gaugeLedCount[]` update automatically — no manual changes needed.

README.md

@@ -1,3 +1,79 @@
 # arduino_gauge_controller
 
 A dedicated gauge controller for Arduinos.
+
+## Overview
+
+This repository contains:
+
+- `Gaugecontroller/Gaugecontroller.ino`: the Arduino Mega firmware for the stepper gauges, LEDs, and integrated HV5812-based VFD
+- `gaugecontroller.yaml`: the ESPHome-based ESP32 firmware that exposes the gauges and VFD to Home Assistant via the native API
+
+## VFD Support
+
+The integrated gauge controller now includes a 4-digit VFD with:
+
+- 4 alphanumeric digits
+- decimal point indicator
+- alarm bell indicator
+
+On the merged Arduino firmware, the HV5812 control pins are:
+
+- `D46` -> `DATA`
+- `D47` -> `CLOCK`
+- `D48` -> `STROBE`
+- `D49` -> `BLANK/OE`
+
+The standalone VFD sketch used `D51/D52/D53/D49`, but `51/52/53` conflict with the gauge stepper pins in the integrated controller.
+
+## Arduino Serial Commands
+
+The merged Arduino firmware accepts:
+
+- `VFD`
+  clears the display and turns off decimal point and alarm bell
+- `VFD 1234`
+- `VFD 0123`
+- `VFD DEAD`
+- `VFD 8888.`
+- `VFD BEEF!`
+- `VFD 12AF.!`
+
+Rules:
+
+- up to 4 characters are displayed
+- valid characters are `0-9`, `A-F`, and `-`
+- `.` enables the decimal point
+- `!` enables the alarm bell
+- shorter values are right-aligned
+- leading zeroes are preserved if they are part of the input
+
+## Home Assistant Integration
+
+The ESPHome firmware in `gaugecontroller.yaml` exposes entities to Home Assistant via the native API:
+
+### Gauge Controls
+- Number entities for each gauge's target value (with unit conversion)
+- Number entities for speed and acceleration (diagnostic)
+- Rezero buttons for each gauge and all gauges
+
+### VFD Display
+- `VFD Display`: text entity for the displayed value
+- `VFD Decimal Point`: switch entity
+- `VFD Alarm`: switch entity
+
+The display is intentionally exposed as a text entity rather than a numeric entity so that:
+
+- leading zeroes are preserved
+- hexadecimal values like `DEAD` or `BEEF` work
+- clearing the display is possible with an empty value
+
+### LED Controls
+- RGB light entity for each gauge's backlight with effects (Blink, Breathe, Double Flash)
+- Binary light entities for each gauge's red/green indicators and status lights
+
+### Diagnostics
+- WiFi signal sensor
+- Uptime sensor
+- IP address and SSID text sensors
+- Arduino Last Message sensor

Rewire_checklist.md

@@ -0,0 +1,323 @@
+# Rewire Checklist
+
+This is a practical rebuild checklist for the current integrated setup:
+
+- `Arduino Mega 2560`
+- `ESP32` running `gauge.py`
+- `HV5812P`
+- 4-digit VFD with decimal point and alarm bell
+- 3 gauge drivers
+- WS2812B LED chain
+
+Use this to rebuild the bench wiring from scratch.
+
+## 1. Power Off Everything
+
+- disconnect all power supplies
+- disconnect USB power if it is currently feeding any board
+- do not move wires while the VFD high-voltage supply is live
+
+## 2. Place The Main Parts
+
+- place the `Arduino Mega 2560`
+- place the `ESP32`
+- place the `HV5812P`
+- place the 3 gauge driver boards
+- place the WS2812B strip connection point
+- place the VFD tube connection point
+
+## 3. Establish A Common Ground First
+
+Before anything else, create one common logic ground network.
+
+Connect:
+
+- `Mega GND` -> ground rail
+- `ESP32 GND` -> same ground rail
+- `HV5812P GND` -> same ground rail
+- `Gauge driver 0 logic GND` -> same ground rail
+- `Gauge driver 1 logic GND` -> same ground rail
+- `Gauge driver 2 logic GND` -> same ground rail
+- `WS2812B GND` -> same ground rail
+
+If your VFD high-voltage supply has a ground/reference return:
+
+- `VFD HV supply return` -> same common ground rail
+
+Do not continue until this common ground is in place.
+
+## 4. Wire The Arduino Mega Power
+
+Connect:
+
+- regulated `5V logic supply` -> `Mega 5V`
+- ground rail -> `Mega GND`
+
+Do not use the Mega to power motors.
+
+## 5. Wire The ESP32 Power
+
+Power the ESP32 in the way your board expects.
+
+Typical options:
+
+- via board USB
+- via board `5V/VIN` if your ESP32 board has its own regulator
+- via regulated `3.3V` if it is a bare module that requires that
+
+Also connect:
+
+- `ESP32 GND` -> common ground rail
+
+Do not feed raw `5V` into a bare `3.3V-only` ESP32 module.
+
+## 6. Wire The ESP32 UART To The Mega
+
+Connect:
+
+- `ESP32 GPIO17 (TX)` -> `Mega pin 19 (RX1)`
+- `ESP32 GPIO16 (RX)` <- `Mega pin 18 (TX1)`
+- `ESP32 GND` -> `Mega GND`
+
+This UART link is used by `gauge.py`.
+
+## 7. Wire The HV5812P Logic Side
+
+Connect:
+
+- `Mega D46` -> `HV5812P DATA IN / DIN`
+- `Mega D47` -> `HV5812P CLOCK / CLK`
+- `Mega D48` -> `HV5812P STROBE / LATCH`
+- `Mega D49` -> `HV5812P BLANKING / OE`
+- `Mega 5V` -> `HV5812P VDD`
+- `Mega GND` -> `HV5812P GND`
+
+Do not connect:
+
+- `Mega 5V` -> `HV5812P VPP`
+
+## 8. Wire The HV5812P High-Voltage Side
+
+Connect:
+
+- `VFD high-voltage positive supply` -> `HV5812P VPP`
+- `VFD high-voltage supply return / reference` -> common ground rail
+
+At this stage:
+
+- `VDD` must be `5V`
+- `VPP` must be your VFD high-voltage rail
+
+## 9. Wire The HV5812P Outputs To The VFD
+
+Connect these one by one:
+
+- `HVOut1` -> VFD segment `A`
+- `HVOut2` -> VFD segment `B`
+- `HVOut3` -> VFD segment `C`
+- `HVOut4` -> VFD segment `D`
+- `HVOut5` -> VFD segment `E`
+- `HVOut6` -> VFD segment `F`
+- `HVOut7` -> VFD segment `G`
+- `HVOut8` -> VFD decimal point segment
+- `HVOut9` -> VFD alarm bell segment
+- `HVOut10` -> VFD digit 1 grid
+- `HVOut11` -> VFD digit 2 grid
+- `HVOut12` -> VFD digit 3 grid
+- `HVOut13` -> VFD digit 4 grid
+- `HVOut14` -> VFD indicator grid between digits 2 and 3
+
+## 10. Wire The VFD Filament
+
+Wire the VFD filament/heater exactly as required by your tube.
+
+This checklist cannot specify the exact filament supply because it depends on the actual tube.
+
+Required reminder:
+
+- do not power the filament from an Arduino GPIO
+- use the correct filament supply for the tube
+
+## 11. Wire Gauge Driver 0
+
+Connect:
+
+- `Mega D50` -> `Gauge driver 0 DIR`
+- `Mega D51` -> `Gauge driver 0 STEP`
+- `Mega GND` -> `Gauge driver 0 logic GND`
+
+Then connect the motor side of that driver to:
+
+- its motor power supply
+- its gauge motor
+
+according to the driver board you are using.
+
+## 12. Wire Gauge Driver 1
+
+Connect:
+
+- `Mega D8` -> `Gauge driver 1 DIR`
+- `Mega D9` -> `Gauge driver 1 STEP`
+- `Mega GND` -> `Gauge driver 1 logic GND`
+
+Then connect the motor side of that driver to:
+
+- its motor power supply
+- its gauge motor
+
+according to the driver board you are using.
+
+## 13. Wire Gauge Driver 2
+
+Connect:
+
+- `Mega D52` -> `Gauge driver 2 DIR`
+- `Mega D53` -> `Gauge driver 2 STEP`
+- `Mega GND` -> `Gauge driver 2 logic GND`
+
+Then connect the motor side of that driver to:
+
+- its motor power supply
+- its gauge motor
+
+according to the driver board you are using.
+
+## 14. Wire The WS2812 LEDs
+
+Connect:
+
+- `Mega D22` -> main backlight/status strip `DIN`
+- `Mega D36` -> indicator strip `DIN`
+- `5V LED supply` -> both strip `5V` inputs
+- both strip `GND` inputs -> common ground rail
+
+If the LED chain is long or bright:
+
+- do not power it from the Mega `5V`
+- use a proper external `5V` supply
+
+## 15. Verify The Pins That Changed For The Integrated VFD
+
+The VFD is no longer on the old standalone pins.
+
+Old standalone pins:
+
+- `D51` -> DATA
+- `D52` -> CLOCK
+- `D53` -> STROBE
+- `D49` -> BLANK
+
+Current integrated pins:
+
+- `D46` -> DATA
+- `D47` -> CLOCK
+- `D48` -> STROBE
+- `D49` -> BLANK
+
+So make sure:
+
+- nothing VFD-related is still on `D51`
+- nothing VFD-related is still on `D52`
+- nothing VFD-related is still on `D53`
+- only `BLANK/OE` remains on `D49`
+
+## 16. Sanity Check Before Powering Logic
+
+Check each item physically:
+
+- `Mega D46` really goes to `HV5812 DATA`
+- `Mega D47` really goes to `HV5812 CLOCK`
+- `Mega D48` really goes to `HV5812 STROBE`
+- `Mega D49` really goes to `HV5812 BLANKING`
+- `Mega D50/D51` only go to gauge driver 0
+- `Mega D8/D9` only go to gauge driver 1
+- `Mega D52/D53` only go to gauge driver 2
+- `Mega D22` only goes to WS2812B `DIN`
+- `ESP32 GPIO17` goes to `Mega RX1`
+- `ESP32 GPIO16` goes to `Mega TX1`
+- all grounds are common
+- `HV5812 VDD` is `5V`
+- `HV5812 VPP` is high voltage, not `5V`
+
+## 17. Power Logic Only First
+
+Apply only logic power first:
+
+- Mega power
+- ESP32 power
+- HV5812 `VDD`
+- WS2812 `5V`
+
+Leave motor supply and VFD high voltage off for the first check if possible.
+
+Verify:
+
+- Mega boots
+- ESP32 boots
+- UART communication works
+
+## 18. Power The VFD High Voltage
+
+Now apply the VFD high-voltage supply to `HV5812 VPP`.
+
+Verify:
+
+- `VDD` remains `5V`
+- `VPP` is the expected high voltage
+- no logic wire is heating
+
+## 19. Power The Gauge Drivers
+
+Now apply motor power to the gauge drivers.
+
+Verify:
+
+- no driver fault LEDs
+- no motor heating or runaway movement immediately on power-up
+
+## 20. First Functional Test
+
+Test in this order:
+
+1. confirm the ESP32 can talk to the Mega
+2. send `VFD 8888`
+3. send `VFD DEAD.!`
+4. test one gauge movement from Home Assistant or MQTT
+5. test one LED output
+
+## 21. If Something Is Wrong
+
+Use this triage order:
+
+1. check grounds
+2. check `VDD` and `VPP`
+3. check Mega pin number mistakes
+4. check crossed UART lines
+5. check that the VFD is still on `46/47/48/49`, not `51/52/53/49`
+
+## 22. Quick Reference
+
+### Mega pins in use
+
+- `D8` -> gauge 1 DIR
+- `D9` -> gauge 1 STEP
+- `D22` -> WS2812 DIN
+- `D46` -> HV5812 DATA
+- `D47` -> HV5812 CLOCK
+- `D48` -> HV5812 STROBE
+- `D49` -> HV5812 BLANKING
+- `D50` -> gauge 0 DIR
+- `D51` -> gauge 0 STEP
+- `D52` -> gauge 2 DIR
+- `D53` -> gauge 2 STEP
+- `D18` -> UART TX1 to ESP32 RX
+- `D19` -> UART RX1 from ESP32 TX
+
+### VFD outputs
+
+- `HVOut1..7` -> `A..G`
+- `HVOut8` -> decimal point
+- `HVOut9` -> alarm bell
+- `HVOut10..13` -> digit grids 1..4
+- `HVOut14` -> indicator grid

Stripboard_layout.md

@@ -0,0 +1,414 @@
+# Stripboard Layout Suggestion
+
+This is a practical suggested layout for moving the current bench wiring onto stripboard. It is not a PCB netlist. It is a placement and routing plan intended to reduce wiring chaos while keeping the high-voltage VFD side separated from the low-voltage logic side.
+
+Use this together with:
+
+- [wiring.md](/home/adebaumann/development/arduino_gauge_controller/wiring.md:1)
+- [Rewire_checklist.md](/home/adebaumann/development/arduino_gauge_controller/Rewire_checklist.md:1)
+
+## Design Goals
+
+- keep `5V logic` on one side
+- keep `VFD high voltage` on the opposite side
+- keep the `HV5812P` between those two domains
+- bring all off-board wiring to clearly labeled edge connectors
+- avoid crossing the gauge step/dir wiring through the VFD area
+- make debugging possible with scope probes and a meter
+
+## Recommended Board Strategy
+
+Use one main stripboard for:
+
+- Arduino Mega interface headers
+- HV5812P and its support wiring
+- connectors for the VFD tube
+- connectors for the three gauge drivers
+- connector for the WS2812 strip
+- connector for the ESP32 UART link
+
+Do not mount the Arduino Mega itself onto stripboard. Use pin headers or screw terminals so the Mega remains removable.
+
+If possible, also do not mount the ESP32 directly unless you already have a reliable carrier board for it.
+
+## Suggested Physical Zoning
+
+Arrange the board in four zones from left to right:
+
+1. `Mega / ESP32 low-voltage I/O zone`
+2. `Gauge / LED connector zone`
+3. `HV5812P driver zone`
+4. `VFD high-voltage and tube connector zone`
+
+That gives you a left-to-right flow like this:
+
+```text
+[ Mega / ESP32 ] [ Gauge + LED connectors ] [ HV5812P ] [ VFD + HV connectors ]
+```
+
+This is better than putting the HV5812 at the edge near the Mega, because the HV5812 is the boundary device between logic and high voltage.
+
+## Board Orientation
+
+Assume the stripboard copper tracks run horizontally.
+
+Recommended use:
+
+- horizontal tracks for local distribution
+- vertical jumps made with insulated wire links
+
+Cut tracks aggressively around the HV5812P so it does not accidentally join unrelated nets through the copper strips.
+
+## Left Side: Mega / ESP32 Interface
+
+Place a row of labeled pin headers or screw terminals for the signals coming from the Mega:
+
+- `5V`
+- `GND`
+- `D22`
+- `D46`
+- `D47`
+- `D48`
+- `D49`
+- `D50`
+- `D51`
+- `D52`
+- `D53`
+- `RX1`
+- `TX1`
+
+Place a second small header for the ESP32:
+
+- `ESP32 TX`
+- `ESP32 RX`
+- `ESP32 GND`
+
+Keep these headers near one board edge so you can unplug and rework them easily.
+
+## Middle-Left: Gauge / LED Connectors
+
+Place four connector groups near the Mega interface side:
+
+1. `Gauge 0`
+   - `DIR`
+   - `STEP`
+   - `GND`
+2. `Gauge 1`
+   - `DIR`
+   - `STEP`
+   - `GND`
+3. `Gauge 2`
+   - `DIR`
+   - `STEP`
+   - `GND`
+4. `WS2812`
+   - `DIN`
+   - `5V`
+   - `GND`
+
+This keeps all low-voltage off-board connections together.
+
+## Center: HV5812P Zone
+
+Mount the `HV5812P` roughly in the center-right of the board.
+
+Reason:
+
+- logic-side control pins can approach from the left
+- high-voltage outputs can leave to the right toward the VFD connector
+
+Around the HV5812P:
+
+- isolate each used pin with track cuts as needed
+- keep short local links for `DATA`, `CLOCK`, `STROBE`, `BLANKING`
+- keep `VDD` decoupling physically close to the chip
+
+Recommended support parts close to the HV5812P:
+
+- `100 nF` ceramic decoupling capacitor between `VDD` and `GND`
+- one larger bulk capacitor on the `5V` rail nearby, for example `10 uF` to `47 uF`
+
+If you already use any datasheet-recommended support parts for the HV side, place them in this same zone.
+
+## Right Side: VFD Connector Zone
+
+Put the VFD connectors on the far right side of the board, physically separated from the Mega headers.
+
+Provide terminals or headers for:
+
+- `HVOut1` -> `A`
+- `HVOut2` -> `B`
+- `HVOut3` -> `C`
+- `HVOut4` -> `D`
+- `HVOut5` -> `E`
+- `HVOut6` -> `F`
+- `HVOut7` -> `G`
+- `HVOut8` -> `DP`
+- `HVOut9` -> `BELL`
+- `HVOut10` -> `GRID1`
+- `HVOut11` -> `GRID2`
+- `HVOut12` -> `GRID3`
+- `HVOut13` -> `GRID4`
+- `HVOut14` -> `GRID_IND`
+
+Also provide separate terminals for:
+
+- `VPP`
+- `GND`
+- filament connections
+
+Keep the filament connections away from the logic-side headers.
+
+## Suggested Power Buses
+
+Use distinct buses and label them clearly:
+
+- `5V LOGIC`
+- `GND`
+- `VPP`
+
+Recommended physical arrangement:
+
+- `5V` bus along the top-left area only
+- `GND` bus available across the board
+- `VPP` bus only on the far-right HV area
+
+Do not run a long exposed `VPP` strip through the entire board. Keep the high-voltage distribution short and local to the HV5812 and VFD connector side.
+
+## Suggested Routing
+
+### Mega to HV5812
+
+Route these as short direct runs:
+
+- `D46` -> `DATA`
+- `D47` -> `CLOCK`
+- `D48` -> `STROBE`
+- `D49` -> `BLANKING`
+
+These should pass from the left interface zone into the HV5812 zone without crossing the VPP area.
+
+### Mega to Gauges
+
+Route these directly to the gauge connector blocks:
+
+- `D50` -> gauge 0 `DIR`
+- `D51` -> gauge 0 `STEP`
+- `D8` and `D9`
+  If you are bringing these through the stripboard too, add them to the Mega header group and route them directly to gauge 1.
+- `D52` -> gauge 2 `DIR`
+- `D53` -> gauge 2 `STEP`
+
+If `D8` and `D9` come from separate fly wires to the stripboard, keep them in the same low-voltage connector area as the rest of the gauge lines.
+
+### Mega to WS2812
+
+Route:
+
+- `D22` -> main backlight/status strip `DIN`
+- `D36` -> indicator strip `DIN`
+- `5V` -> both strip `5V` inputs
+- `GND` -> both strip `GND` inputs
+
+Keep the LED connector in the low-voltage area.
+
+### ESP32 to Mega
+
+If the stripboard is acting as the interconnect backplane:
+
+- `ESP32 TX` -> `Mega RX1`
+- `ESP32 RX` -> `Mega TX1`
+- `ESP32 GND` -> `GND`
+
+## Track Cuts and Links
+
+Recommended stripboard discipline:
+
+- every IC pin should be visually checked for unintended strip continuity
+- cut under or near pins wherever two adjacent pins must not share the strip
+- use insulated jumpers for crossings instead of relying on long exposed component leads
+- use a continuity meter after every 5-10 wires added
+
+For the HV5812P specifically:
+
+- assume most adjacent pins must not be left on the same uninterrupted strip
+- cut first, then add intentional links
+
+## Physical Separation Rules
+
+Keep these separations:
+
+- logic and UART wiring away from `VPP`
+- VFD output traces away from ESP32 and Mega headers
+- gauge step/dir traces away from VFD high-voltage outputs where possible
+
+If you can, leave at least one empty strip gap between low-voltage and high-voltage routing regions, and more where practical.
+
+## Labeling
+
+Label the board directly with marker or printed tape.
+
+At minimum label:
+
+- `5V`
+- `GND`
+- `VPP`
+- `DIN`
+- `CLK`
+- `STR`
+- `BLK`
+- `G0 DIR`
+- `G0 STEP`
+- `G1 DIR`
+- `G1 STEP`
+- `G2 DIR`
+- `G2 STEP`
+- `LED DIN`
+- `RX1`
+- `TX1`
+- `A B C D E F G DP BELL G1 G2 G3 G4 GI`
+
+This matters more than aesthetics. A labeled board is much easier to repair later.
+
+## Practical Build Order
+
+1. Place and mark the four physical zones.
+2. Mount the low-voltage connector headers.
+3. Mount the HV5812P.
+4. Cut all required strips around the HV5812P before adding wires.
+5. Add `GND` and `5V` low-voltage distribution.
+6. Add Mega-to-HV5812 logic lines.
+7. Add gauge and LED connector routing.
+8. Add `VPP` and the VFD output connector routing.
+9. Add the VFD filament connector.
+10. Verify continuity and shorts before any power is applied.
+
+## Recommended First Continuity Checks
+
+Before power:
+
+- `5V` is not shorted to `GND`
+- `VPP` is not shorted to `GND`
+- `VPP` is not shorted to `5V`
+- `D46/D47/D48/D49` are only connected to the intended HV5812 pins
+- `D50/D51/D52/D53/D8/D9` are only connected to the intended gauge connectors
+- `D22` only goes to the WS2812 connector
+- `RX1/TX1` are not swapped at the stripboard labels
+
+## Suggested Board Size
+
+For comfort rather than minimum size, use a board large enough to avoid crowding:
+
+- roughly `100 x 160 mm` or larger if you want good service access
+
+Smaller is possible, but with mixed logic, UART, gauge control, LEDs, and VFD high voltage, cramped stripboard becomes harder to debug than a rat's nest.
+
+## Recommendation
+
+If you want the cleanest result:
+
+- use the stripboard only as an interconnect backplane
+- keep the Mega, ESP32, and possibly the gauge drivers off-board on removable connectors
+- keep the HV5812 and VFD connector area on the stripboard itself
+
+That gives you most of the neatness benefit without forcing the whole system into one dense board.
+
+## ASCII Top View
+
+This is a suggested top-view arrangement, not a strict scale drawing.
+
+```text
+Top edge
+
++--------------------------------------------------------------------------------------------------+
+| [Mega Header Block]                [Gauge / LED Connectors]          [HV5812P Zone] [VFD Zone] |
+|                                                                                                  |
+|  5V  GND  D22  D46  D47  D48  D49  D50  D51  D52  D53  RX1  TX1                                 |
+|  o    o    o    o    o    o    o    o    o    o    o    o    o                                  |
+|                                                                                                  |
+|  [ESP32 Header]                                                                                  |
+|  TX   RX   GND                                                                                   |
+|  o    o    o                                                                                     |
+|                                                                                                  |
+|                                [Gauge 0]   [Gauge 1]   [Gauge 2]   [WS2812]                     |
+|                                DIR STEP G  DIR STEP G  DIR STEP G  DIN 5V G                     |
+|                                 o   o   o   o   o   o   o   o   o   o  o  o                     |
+|                                                                                                  |
+|                                                            +----------------------+              |
+|                                                            |      HV5812P         |              |
+|                                                            |                      |              |
+|  5V LOGIC BUS ============================================>| VDD                  |              |
+|  GND BUS      ============================================>| GND                  |==============|
+|                                                            | DIN  CLK STR BLK     |              |
+|                                                            |  ^    ^   ^   ^      |              |
+|                                                            +--|----|---|---|------+              |
+|                                                               |    |   |   |                     |
+|                                                               |    |   |   +---- D49             |
+|                                                               |    |   +-------- D48             |
+|                                                               |    +------------ D47             |
+|                                                               +----------------- D46             |
+|                                                                                                  |
+|                                                                               VPP terminal       |
+|                                                                               o                  |
+|                                                                               |                  |
+|  HV AREA                                                                     |                  |
+|  kept to right side only                                                     |                  |
+|                                                                               v                  |
+|                                                         A  B  C  D  E  F  G  DP BELL G1 G2 G3 G4 GI
+|                                                         o  o  o  o  o  o  o  o   o    o  o  o  o  o
+|                                                         [VFD output connector block]             |
+|                                                                                                  |
+|                                                         FIL_A  FIL_B  GND/HVRET                  |
+|                                                          o      o       o                        |
+|                                                         [filament / HV return terminals]         |
+|                                                                                                  |
++--------------------------------------------------------------------------------------------------+
+
+Bottom edge
+```
+
+## Reading The Sketch
+
+- left side:
+  all low-voltage headers from the Mega and ESP32
+- center-left:
+  gauge and LED connector blocks
+- center-right:
+  HV5812P
+- far right:
+  VFD outputs, filament, and `VPP`
+
+This keeps the dangerous and noisy wiring concentrated on one side of the board.
+
+## Suggested Copper-Strip Use
+
+If your strips run horizontally:
+
+- use upper strips for low-voltage headers and distribution
+- use middle strips for gauge and LED routing
+- isolate the HV5812P pin rows heavily with track cuts
+- use lower-right strips only for the VFD output area and `VPP`
+
+## Suggested Connector Edge Placement
+
+If you want the board to be easy to service:
+
+- put Mega and ESP32 headers on the left edge
+- put gauge and LED connectors on the bottom edge
+- put VFD and high-voltage terminals on the right edge
+
+That way:
+
+- low-voltage control cables enter from the left and bottom
+- high-voltage VFD wires leave only on the right
+
+## Minimum Clearance Advice
+
+On stripboard, do not pack the `VPP` and VFD output terminals tightly against the low-voltage headers.
+
+Practical suggestion:
+
+- leave at least several empty holes / one empty strip region between the HV5812 logic-side routing and the `VPP` / VFD connector zone
+- if you have room, leave more than that
+
+More separation is better than a dense layout here.

VFDStandalone/Pinout.md

@@ -0,0 +1,56 @@
+# Pinout
+
+This project uses an Arduino Mega 2560 with an `HV5812P` high-voltage shift register / latch driver.
+
+The sketch in [VFDStandalone.ino](/home/adebaumann/development/arduino_gauge_controller/VFDStandalone/VFDStandalone.ino:1) currently expects these logic connections.
+
+## Arduino Mega 2560 -> HV5812P
+
+| Mega Pin | Mega Function | HV5812P Signal | Notes |
+|---|---|---|---|
+| `D51` | `MOSI` | `DATA` / `DIN` | Serial data into the HV5812P |
+| `D52` | `SCK` | `CLOCK` / `CLK` | Shift clock |
+| `D53` | `SS` | `LATCH` / `STROBE` | Transfers shifted bits to the outputs |
+| `D49` | GPIO | `BLANK` / `OE` | Optional. Set `kHvBlankPin = -1` in the sketch if unused |
+| `GND` | Ground | Logic `GND` | Mega and HV5812P logic ground must be common |
+
+## HV5812P Outputs -> VFD Tube
+
+| HV5812P Output | Function |
+|---|---|
+| `HVOut1` | Segment `A` |
+| `HVOut2` | Segment `B` |
+| `HVOut3` | Segment `C` |
+| `HVOut4` | Segment `D` |
+| `HVOut5` | Segment `E` |
+| `HVOut6` | Segment `F` |
+| `HVOut7` | Segment `G` |
+| `HVOut8` | Decimal point segment |
+| `HVOut9` | Alarm bell segment |
+| `HVOut10` | Digit grid 1 |
+| `HVOut11` | Digit grid 2 |
+| `HVOut12` | Digit grid 3 |
+| `HVOut13` | Digit grid 4 |
+| `HVOut14` | Indicator grid between digits 2 and 3 |
+
+## Serial Input Format
+
+Examples supported by the sketch:
+
+- `1234` -> digits only
+- `1234.` -> decimal point on
+- `1234!` -> alarm bell on
+- `1234.!` -> decimal point and alarm bell on
+
+## Power and Safety Notes
+
+- The Arduino `5V` pin is for the logic side only.
+- The HV5812P also needs its required logic supply and high-voltage supply per the datasheet.
+- The VFD filament, grid, and segment high-voltage wiring are separate from the Arduino logic pins.
+- Do not connect any high-voltage VFD node directly to the Arduino Mega.
+- If the blanking behavior is inverted on your board, change `kBlankActiveHigh` in the sketch.
+
+## Important
+
+This file names the functional signals on the `HV5812P`, not the package pin numbers.
+If you want a package-pin wiring table too, I can add one once you confirm the exact datasheet variant / package orientation you are using.

VFDStandalone/VFDStandalone.ino

@@ -0,0 +1,342 @@
+// Arduino Mega 2560 + HV5812P VFD driver
+//
+// Tube wiring:
+// - HVOut1..HVOut7  -> digit segments A..G
+// - HVOut8          -> decimal point segment on the indicator grid
+// - HVOut9          -> alarm bell segment on the indicator grid
+// - HVOut10..HVOut13 -> digits 1..4
+// - HVOut14         -> indicator grid between digits 2 and 3
+//
+// Send an integer over the USB serial port and it will be shown on the VFD.
+// Examples:
+//   42<newline>
+//   -17<newline>
+//   1234.<newline>   // enables the decimal point
+//   1234!<newline>   // enables the alarm bell
+//   1234.!<newline>  // enables both
+
+#include <Arduino.h>
+
+namespace {
+
+constexpr uint8_t kHvDataPin = 51;   // MOSI on Mega 2560
+constexpr uint8_t kHvClockPin = 52;  // SCK on Mega 2560
+constexpr uint8_t kHvLatchPin = 53;  // User-configurable latch/strobe pin
+constexpr int8_t kHvBlankPin = 49;   // Set to -1 if BL/OE is not connected
+constexpr bool kBlankActiveHigh = true;
+
+constexpr unsigned long kSerialBaud = 115200;
+constexpr unsigned long kDigitHoldMicros = 2000;
+
+constexpr uint8_t kDigitCount = 4;
+constexpr uint8_t kSegmentCount = 7;
+constexpr uint8_t kDriverBits = 20;
+
+constexpr uint8_t kSegmentStartBit = 0;  // HVOut1 -> bit 0
+constexpr uint8_t kPointSegmentBit = 7;  // HVOut8 -> bit 7
+constexpr uint8_t kBellSegmentBit = 8;   // HVOut9 -> bit 8
+constexpr uint8_t kGridStartBit = 9;     // HVOut10 -> bit 9
+constexpr uint8_t kIndicatorGridBit = 13;  // HVOut14 -> bit 13
+
+char g_displayBuffer[kDigitCount] = {' ', ' ', ' ', ' '};
+char g_inputBuffer[16];
+uint8_t g_inputLength = 0;
+bool g_pointEnabled = false;
+bool g_bellEnabled = false;
+uint8_t g_rawOutput = 0;
+
+// Seven-segment encoding order is A, B, C, D, E, F, G.
+uint8_t encodeCharacter(char c) {
+  switch (c) {
+    case '0': return 0b0111111;
+    case '1': return 0b0000110;
+    case '2': return 0b1011011;
+    case '3': return 0b1001111;
+    case '4': return 0b1100110;
+    case '5': return 0b1101101;
+    case '6': return 0b1111101;
+    case '7': return 0b0000111;
+    case '8': return 0b1111111;
+    case '9': return 0b1101111;
+    case 'A':
+    case 'a': return 0b1110111;
+    case 'B':
+    case 'b': return 0b1111100;
+    case 'C':
+    case 'c': return 0b0111001;
+    case 'D':
+    case 'd': return 0b1011110;
+    case 'E':
+    case 'e': return 0b1111001;
+    case 'F':
+    case 'f': return 0b1110001;
+    case '-': return 0b1000000;
+    default: return 0;
+  }
+}
+
+void shiftDriverWord(uint32_t word) {
+  digitalWrite(kHvLatchPin, HIGH);
+  digitalWrite(kHvClockPin, HIGH);
+
+  for (int8_t bit = kDriverBits - 1; bit >= 0; --bit) {
+    digitalWrite(kHvDataPin, (word >> bit) & 0x1U ? HIGH : LOW);
+    digitalWrite(kHvClockPin, LOW);
+    digitalWrite(kHvClockPin, HIGH);
+  }
+
+  digitalWrite(kHvLatchPin, LOW);
+  digitalWrite(kHvLatchPin, HIGH);
+}
+
+void setDisplayBlanked(bool blanked) {
+  if (kHvBlankPin < 0) {
+    return;
+  }
+
+  const bool level = kBlankActiveHigh ? blanked : !blanked;
+  digitalWrite(kHvBlankPin, level ? HIGH : LOW);
+}
+
+void blankDisplay() {
+  shiftDriverWord(0);
+}
+
+uint32_t maskForHvOutput(uint8_t hvOutput) {
+  if (hvOutput == 0 || hvOutput > kDriverBits) {
+    return 0;
+  }
+
+  return 1UL << (hvOutput - 1);
+}
+
+void renderDigit(uint8_t digitIndex) {
+  uint32_t word = 0;
+  const uint8_t segments = encodeCharacter(g_displayBuffer[digitIndex]);
+
+  for (uint8_t segment = 0; segment < kSegmentCount; ++segment) {
+    if ((segments >> segment) & 0x1U) {
+      word |= (1UL << (kSegmentStartBit + segment));
+    }
+  }
+
+  word |= (1UL << (kGridStartBit + digitIndex));
+  shiftDriverWord(word);
+}
+
+void renderIndicator() {
+  uint32_t word = 1UL << kIndicatorGridBit;
+
+  if (g_pointEnabled) {
+    word |= 1UL << kPointSegmentBit;
+  }
+
+  if (g_bellEnabled) {
+    word |= 1UL << kBellSegmentBit;
+  }
+
+  shiftDriverWord(word);
+}
+
+void writeTextToDisplay(const char* text) {
+  for (uint8_t i = 0; i < kDigitCount; ++i) {
+    g_displayBuffer[i] = ' ';
+  }
+
+  size_t len = strlen(text);
+  if (len > kDigitCount) {
+    text += len - kDigitCount;
+    len = kDigitCount;
+  }
+
+  const uint8_t start = kDigitCount - len;
+  for (uint8_t i = 0; i < len; ++i) {
+    g_displayBuffer[start + i] = text[i];
+  }
+}
+
+void setDisplayFromNumber(long value) {
+  char buffer[16];
+  ltoa(value, buffer, 10);
+  writeTextToDisplay(buffer);
+}
+
+bool parseDisplayCommand(const char* input,
+                         char* displayText,
+                         size_t displayTextSize,
+                         bool& pointEnabled,
+                         bool& bellEnabled) {
+  size_t inputIndex = 0;
+  size_t displayIndex = 0;
+
+  if (input[inputIndex] == '-') {
+    if (displayIndex + 1 >= displayTextSize) {
+      return false;
+    }
+    displayText[displayIndex++] = input[inputIndex++];
+  }
+
+  const size_t digitStart = inputIndex;
+  while (isxdigit(static_cast<unsigned char>(input[inputIndex]))) {
+    if (displayIndex + 1 >= displayTextSize) {
+      return false;
+    }
+    displayText[displayIndex] = toupper(static_cast<unsigned char>(input[inputIndex]));
+    ++displayIndex;
+    ++inputIndex;
+  }
+
+  if (inputIndex == digitStart) {
+    return false;
+  }
+
+  pointEnabled = false;
+  bellEnabled = false;
+
+  while (input[inputIndex] != '\0') {
+    if (input[inputIndex] == '.') {
+      pointEnabled = true;
+    } else if (input[inputIndex] == '!') {
+      bellEnabled = true;
+    } else {
+      return false;
+    }
+    ++inputIndex;
+  }
+
+  displayText[displayIndex] = '\0';
+  return true;
+}
+
+bool parseRawOutputCommand(const char* input, uint8_t& hvOutput) {
+  if (strncmp(input, "RAW ", 4) != 0) {
+    return false;
+  }
+
+  char* endPtr = nullptr;
+  const long parsed = strtol(input + 4, &endPtr, 10);
+  if (*endPtr != '\0' || parsed < 0 || parsed > kDriverBits) {
+    return false;
+  }
+
+  hvOutput = static_cast<uint8_t>(parsed);
+  return true;
+}
+
+void commitSerialBuffer() {
+  if (g_inputLength == 0) {
+    return;
+  }
+
+  g_inputBuffer[g_inputLength] = '\0';
+
+  uint8_t rawOutput = 0;
+  if (parseRawOutputCommand(g_inputBuffer, rawOutput)) {
+    g_rawOutput = rawOutput;
+    if (g_rawOutput == 0) {
+      Serial.println(F("RAW mode OFF"));
+    } else {
+      Serial.print(F("RAW mode: HVOUT"));
+      Serial.println(g_rawOutput);
+    }
+    g_inputLength = 0;
+    return;
+  }
+
+  char displayText[16];
+  bool pointEnabled = false;
+  bool bellEnabled = false;
+  if (parseDisplayCommand(g_inputBuffer, displayText, sizeof(displayText), pointEnabled, bellEnabled)) {
+    g_rawOutput = 0;
+    writeTextToDisplay(displayText);
+    g_pointEnabled = pointEnabled;
+    g_bellEnabled = bellEnabled;
+    Serial.print(F("Displaying: "));
+    Serial.println(displayText);
+    Serial.print(F("Point: "));
+    Serial.println(g_pointEnabled ? F("ON") : F("OFF"));
+    Serial.print(F("Bell: "));
+    Serial.println(g_bellEnabled ? F("ON") : F("OFF"));
+  } else {
+    Serial.print(F("Ignored invalid input: "));
+    Serial.println(g_inputBuffer);
+  }
+
+  g_inputLength = 0;
+}
+
+void pollSerial() {
+  while (Serial.available() > 0) {
+    const char incoming = static_cast<char>(Serial.read());
+
+    if (incoming == '\r' || incoming == '\n') {
+      commitSerialBuffer();
+      continue;
+    }
+
+    if (incoming == '\b' || incoming == 127) {
+      if (g_inputLength > 0) {
+        --g_inputLength;
+      }
+      continue;
+    }
+
+    if (g_inputLength < sizeof(g_inputBuffer) - 1) {
+      g_inputBuffer[g_inputLength++] = incoming;
+    }
+  }
+}
+
+void refreshDisplay() {
+  if (g_rawOutput != 0) {
+    setDisplayBlanked(true);
+    shiftDriverWord(maskForHvOutput(g_rawOutput));
+    setDisplayBlanked(false);
+    delayMicroseconds(kDigitHoldMicros);
+    return;
+  }
+
+  static uint8_t currentPhase = 0;
+
+  setDisplayBlanked(true);
+  if (currentPhase < kDigitCount) {
+    renderDigit(currentPhase);
+  } else if (g_pointEnabled || g_bellEnabled) {
+    renderIndicator();
+  } else {
+    blankDisplay();
+  }
+  setDisplayBlanked(false);
+  delayMicroseconds(kDigitHoldMicros);
+  setDisplayBlanked(true);
+
+  currentPhase = (currentPhase + 1) % (kDigitCount + 1);
+}
+
+}  // namespace
+
+void setup() {
+  pinMode(kHvDataPin, OUTPUT);
+  pinMode(kHvClockPin, OUTPUT);
+  pinMode(kHvLatchPin, OUTPUT);
+  if (kHvBlankPin >= 0) {
+    pinMode(kHvBlankPin, OUTPUT);
+  }
+
+  digitalWrite(kHvDataPin, LOW);
+  digitalWrite(kHvClockPin, HIGH);
+  digitalWrite(kHvLatchPin, HIGH);
+  setDisplayBlanked(true);
+
+  Serial.begin(kSerialBaud);
+  writeTextToDisplay("0");
+  blankDisplay();
+
+  Serial.println(F("HV5812P VFD controller ready."));
+  Serial.println(F("Send an integer followed by newline."));
+}
+
+void loop() {
+  pollSerial();
+  refreshDisplay();
+}

archive/config.example.json

@@ -0,0 +1,59 @@
+{
+  "debug": false,
+
+  "wifi_ssid": "MyNetwork",
+  "wifi_password": "MyPassword",
+
+  "mqtt_broker": "192.168.1.10",
+  "mqtt_port": 1883,
+  "mqtt_user": "mqtt_user",
+  "mqtt_password": "mqtt_password",
+  "mqtt_client_id": "gauge_controller",
+  "mqtt_prefix": "gauges",
+
+  "heartbeat_ms": 10000,
+  "rezero_interval_ms": 3600000,
+
+  "device": {
+    "name": "Selsyn Multi",
+    "model": "Chernobyl Selsyn-inspired gauge",
+    "manufacturer": "AdeBaumann",
+    "area": "Control Panels"
+  },
+
+  "arduino_uart": 1,
+  "arduino_tx_pin": 17,
+  "arduino_rx_pin": 16,
+  "arduino_baud": 115200,
+
+  "gauges": [
+    {
+      "name": "Gauge 1",
+      "entity_name": "Selsyn 1 Power",
+      "min": 0,
+      "max": 7300,
+      "max_steps": 4000,
+      "speed": 5000,
+      "acceleration": 6000,
+      "unit": "W",
+      "leds": {
+        "ws2812_red":   [255, 0, 0],
+        "ws2812_green": [0, 255, 0]
+      }
+    },
+    {
+      "name": "Gauge 2",
+      "entity_name": "Selsyn 2 Power",
+      "min": 0,
+      "max": 7300,
+      "max_steps": 4000,
+      "speed": 5000,
+      "acceleration": 6000,
+      "unit": "W",
+      "leds": {
+        "ws2812_red":   [255, 0, 0],
+        "ws2812_green": [0, 255, 0]
+      }
+    }
+  ]
+}

archive/main.py

@@ -0,0 +1 @@
+import gauge

archive/ota.py

@@ -0,0 +1,474 @@
+"""
+ota.py — Gitea OTA updater for ESP32 / MicroPython
+
+Call ota.update() from boot.py before importing anything else.
+If the update or the subsequent boot fails, the updater retries
+on the next boot rather than bricking the device.
+
+Strategy
+--------
+1. Check if last boot was good (OK flag exists).
+2. If good, fetch remote commit SHA and compare with local — if unchanged,
+   skip file check entirely.
+3. If new commit or failed boot, fetch ota_manifest.txt from the repo
+   to determine which files to sync.
+4. Compare SHA1 hashes with a local manifest (.ota_manifest.json).
+5. Download only changed or missing files, writing to .tmp first.
+6. On success, rename .tmp files into place and update the manifest.
+7. If anything fails mid-update, the manifest is not updated, so the
+   next boot will retry. Partially written .tmp files are cleaned up.
+8. A "safety" flag file (.ota_ok) is written by main.py on successful
+   startup. If it is absent on boot, the previous update is suspected
+   bad — the manifest is wiped so all files are re-fetched cleanly.
+
+Manifest format (ota_manifest.txt)
+---------------------------------
+Each line specifies a file or directory to include:
+    boot.py          # specific file
+    ota.py           # another file
+    selsyn/          # entire directory (trailing slash)
+    lib/             # another directory
+    *.py             # wildcard (matches anywhere)
+    selsyn/*.py      # wildcard in subdirectory
+
+Usage in boot.py
+----------------
+    import ota
+    ota.update()
+    # imports of main etc. go here
+
+Configuration
+-------------
+Edit the block below, or override from a local config file
+(see SETTINGS_FILE).  All settings can be left as module-level
+constants or placed in /ota_config.json:
+    {
+        "gitea_base": "http://git.baumann.gr",
+        "repo_owner": "adebaumann",
+        "repo_name":  "HomeControlPanel",
+        "repo_folder": "firmware",
+        "repo_branch": "main",
+        "api_token":   "nicetry-nothere"
+    }
+"""
+
+import os
+import gc
+import sys
+import ujson
+import urequests
+import utime
+
+# ---------------------------------------------------------------------------
+# Default configuration — override via /ota_config.json
+# ---------------------------------------------------------------------------
+
+GITEA_BASE = "http://git.baumann.gr"  # no trailing slash
+REPO_OWNER = "adrian"
+REPO_NAME = "esp32-gauge"
+REPO_FOLDER = "firmware"  # folder inside repo to sync
+REPO_BRANCH = "main"
+API_TOKEN = None  # set to string for private repos
+
+WIFI_SSID = None
+WIFI_PASSWORD = None
+
+SETTINGS_FILE = "/ota_config.json"
+MANIFEST_FILE = "/.ota_manifest.json"
+OK_FLAG_FILE = "/.ota_ok"
+OTA_MANIFEST = "ota_manifest.txt"
+
+# ---------------------------------------------------------------------------
+# Logging
+# ---------------------------------------------------------------------------
+
+
+def _ts():
+    ms = utime.ticks_ms()
+    return f"{(ms // 3600000) % 24:02d}:{(ms // 60000) % 60:02d}:{(ms // 1000) % 60:02d}.{ms % 1000:03d}"
+
+
+def _log(level, msg):
+    print(f"[{_ts()}] {level:5s}  [OTA] {msg}")
+
+
+def info(msg):
+    _log("INFO", msg)
+
+
+def warn(msg):
+    _log("WARN", msg)
+
+
+def log_err(msg):
+    _log("ERROR", msg)
+
+
+# ---------------------------------------------------------------------------
+# HTTP helpers
+# ---------------------------------------------------------------------------
+
+
+def _headers():
+    h = {"Accept": "application/json"}
+    if API_TOKEN:
+        h["Authorization"] = f"token {API_TOKEN}"
+    return h
+
+
+# ---------------------------------------------------------------------------
+# Config loader
+# ---------------------------------------------------------------------------
+
+
+def load_config():
+    global \
+        GITEA_BASE, \
+        REPO_OWNER, \
+        REPO_NAME, \
+        REPO_FOLDER, \
+        REPO_BRANCH, \
+        API_TOKEN, \
+        WIFI_SSID, \
+        WIFI_PASSWORD
+    try:
+        with open(SETTINGS_FILE) as f:
+            cfg = ujson.load(f)
+        GITEA_BASE = cfg.get("gitea_base", GITEA_BASE)
+        REPO_OWNER = cfg.get("repo_owner", REPO_OWNER)
+        REPO_NAME = cfg.get("repo_name", REPO_NAME)
+        REPO_FOLDER = cfg.get("repo_folder", REPO_FOLDER)
+        REPO_BRANCH = cfg.get("repo_branch", REPO_BRANCH)
+        API_TOKEN = cfg.get("api_token", API_TOKEN)
+        WIFI_SSID = cfg.get("wifi_ssid", WIFI_SSID)
+        WIFI_PASSWORD = cfg.get("wifi_password", WIFI_PASSWORD)
+        info(f"Config loaded from {SETTINGS_FILE}")
+    except OSError:
+        info(f"No {SETTINGS_FILE} found — using defaults")
+    except Exception as e:
+        warn(f"Config parse error: {e} — using defaults")
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _match_pattern(name, pattern):
+    if "*" not in pattern:
+        return name == pattern
+    i, n = 0, len(pattern)
+    j, m = 0, len(name)
+    star = -1
+    while i < n and j < m:
+        if pattern[i] == "*":
+            star = i
+            i += 1
+        elif pattern[i] == name[j]:
+            i += 1
+            j += 1
+        elif star >= 0:
+            i = star + 1
+            j += 1
+        else:
+            return False
+    while i < n and pattern[i] == "*":
+        i += 1
+    return i == n and j == m
+
+
+def _fetch_commit_sha():
+    url = f"{GITEA_BASE}/api/v1/repos/{REPO_OWNER}/{REPO_NAME}/branches/{REPO_BRANCH}"
+    try:
+        r = urequests.get(url, headers=_headers())
+        if r.status_code == 200:
+            data = r.json()
+            r.close()
+            return data.get("commit", {}).get("id")
+        r.close()
+    except Exception as e:
+        log_err(f"Failed to fetch commit: {e}")
+    return None
+
+
+def _fetch_manifest():
+    url = (
+        f"{GITEA_BASE}/api/v1/repos/{REPO_OWNER}/{REPO_NAME}"
+        f"/contents/{OTA_MANIFEST}?ref={REPO_BRANCH}"
+    )
+    try:
+        r = urequests.get(url, headers=_headers())
+        try:
+            if r.status_code == 200:
+                data = r.json()
+                if data.get("content"):
+                    import ubinascii
+
+                    content = ubinascii.a2b_base64(data["content"]).decode()
+                    patterns = [line.strip() for line in content.splitlines()]
+                    return [p for p in patterns if p and not p.startswith("#")]
+            else:
+                warn(f"Manifest not found at {OTA_MANIFEST}")
+        finally:
+            r.close()
+    except Exception as e:
+        log_err(f"Failed to fetch manifest: {e}")
+    return None
+
+
+def _fetch_dir(path):
+    url = (
+        f"{GITEA_BASE}/api/v1/repos/{REPO_OWNER}/{REPO_NAME}"
+        f"/contents/{path}?ref={REPO_BRANCH}"
+    )
+    return _api_get(url)
+
+
+def _api_get(url):
+    """GET a URL and return parsed JSON, or None on failure."""
+    try:
+        r = urequests.get(url, headers=_headers())
+        if r.status_code == 200:
+            data = r.json()
+            r.close()
+            return data
+        warn(f"HTTP {r.status_code} for {url}")
+        r.close()
+    except Exception as e:
+        log_err(f"GET {url} failed: {e}")
+    return None
+
+
+def _download(url, dest_path):
+    """Download url to dest_path. Returns True on success."""
+    tmp = dest_path + ".tmp"
+    try:
+        r = urequests.get(url, headers=_headers())
+        if r.status_code != 200:
+            warn(f"Download failed HTTP {r.status_code}: {url}")
+            r.close()
+            return False
+        with open(tmp, "wb") as f:
+            f.write(r.content)
+        r.close()
+        # Rename into place
+        try:
+            os.remove(dest_path)
+        except OSError:
+            pass
+        os.rename(tmp, dest_path)
+        return True
+    except Exception as e:
+        log_err(f"Download error {url}: {e}")
+        try:
+            os.remove(tmp)
+        except OSError:
+            pass
+        return False
+
+
+def _load_manifest():
+    try:
+        with open(MANIFEST_FILE) as f:
+            return ujson.load(f)
+    except Exception:
+        return {}
+
+
+def _save_manifest(manifest, commit_sha=None):
+    try:
+        with open(MANIFEST_FILE, "w") as f:
+            if commit_sha:
+                manifest["_commit"] = commit_sha
+            ujson.dump(manifest, f)
+    except Exception as e:
+        warn(f"Could not save manifest: {e}")
+
+
+
+def _ok_flag_exists():
+    try:
+        os.stat(OK_FLAG_FILE)
+        return True
+    except OSError:
+        return False
+
+
+def _clear_ok_flag():
+    try:
+        os.remove(OK_FLAG_FILE)
+    except OSError:
+        pass
+
+
+def mark_ok():
+    """
+    Call this from main.py after successful startup.
+    Signals to the OTA updater that the last update was good.
+    """
+    try:
+        with open(OK_FLAG_FILE, "w") as f:
+            f.write("ok")
+    except Exception as e:
+        warn(f"Could not write OK flag: {e}")
+
+
+# ---------------------------------------------------------------------------
+# Core update logic
+# ---------------------------------------------------------------------------
+
+
+def _fetch_file_list():
+    """
+    Returns list of {name, sha, download_url} dicts based on the
+    ota_manifest.txt patterns in the repo folder, or None on failure.
+    """
+    manifest_patterns = _fetch_manifest()
+    if manifest_patterns is None:
+        log_err("No manifest — cannot determine what to fetch")
+        return None
+
+    info(f"Manifest patterns: {manifest_patterns}")
+    files = []
+    visited = set()
+
+    def fetch_matching(entries, patterns):
+        for entry in entries:
+            if entry.get("type") == "dir":
+                for p in patterns:
+                    if p.endswith("/") and entry["name"].startswith(p.rstrip("/")):
+                        sub = _fetch_dir(entry["path"])
+                        if sub:
+                            fetch_matching(sub, patterns)
+                        break
+            else:
+                name = entry["name"]
+                for p in patterns:
+                    p = p.rstrip("/")
+                    if _match_pattern(name, p) or _match_pattern(entry["path"], p):
+                        if entry["path"] not in visited:
+                            visited.add(entry["path"])
+                            files.append(
+                                {
+                                    "name": entry["path"],
+                                    "sha": entry["sha"],
+                                    "download_url": entry["download_url"],
+                                }
+                            )
+                        break
+
+    root = _fetch_dir(REPO_FOLDER)
+    if root is None:
+        return None
+
+    fetch_matching(root, manifest_patterns)
+    return files
+
+
+def _do_update(commit_sha=None):
+    """
+    Fetch file list, download changed files, update manifest.
+    Returns True if all succeeded (or nothing needed updating).
+    """
+    info(
+        f"Checking {GITEA_BASE}/{REPO_OWNER}/{REPO_NAME}/{REPO_FOLDER} @ {REPO_BRANCH}"
+    )
+    file_list = _fetch_file_list()
+    if file_list is None:
+        log_err("Could not fetch file list — skipping update")
+        return False
+
+    info(f"Found {len(file_list)} file(s) to sync")
+    manifest = _load_manifest()
+    updated = []
+    failed = []
+
+    for entry in file_list:
+        name = entry["name"]
+        sha = entry["sha"]
+
+        if manifest.get(name) == sha:
+            info(f"  {name}  up to date")
+            continue
+
+        info(f"  {name}  updating (sha={sha[:8]}...)")
+        gc.collect()
+        ok = _download(entry["download_url"], f"/{name}")
+        if ok:
+            manifest[name] = sha
+            updated.append(name)
+            info(f"  {name}  OK")
+        else:
+            failed.append(name)
+            log_err(f"  {name}  FAILED")
+
+    if failed:
+        log_err(f"Update incomplete — {len(failed)} file(s) failed: {failed}")
+        _save_manifest(manifest, commit_sha)
+        return False
+
+    _save_manifest(manifest, commit_sha)
+
+    if updated:
+        info(f"Update complete — {len(updated)} file(s) updated: {updated}")
+    else:
+        info("All files up to date — nothing to do")
+
+    return True
+
+
+# ---------------------------------------------------------------------------
+# Public entry point
+# ---------------------------------------------------------------------------
+
+
+def update():
+    """
+    Main entry point. Call from boot.py before importing application code.
+
+    - If the OK flag is missing, the previous boot is assumed to have
+      failed — wipes the manifest so everything is re-fetched cleanly.
+    - If the commit hash hasn't changed and last boot was good, skip
+      file comparison entirely.
+    - Runs the update.
+    - Clears the OK flag so main.py must re-assert it on successful start.
+    """
+    info("=" * 40)
+    info("OTA updater starting")
+    info("=" * 40)
+
+    load_config()
+
+    ok_flag = _ok_flag_exists()
+    manifest = _load_manifest()
+
+    if not ok_flag:
+        warn("OK flag missing — last boot may have failed")
+        warn("Re-checking all files, will only download changed ones")
+    else:
+        info("OK flag present — last boot was good")
+
+    commit_sha = _fetch_commit_sha()
+
+    if ok_flag and commit_sha and manifest.get("_commit") == commit_sha:
+        info(f"Commit unchanged ({commit_sha[:8]}) — skipping file check")
+        info("-" * 40)
+        return
+
+    if commit_sha:
+        info(f"Remote commit: {commit_sha[:8]}")
+    else:
+        warn("Could not fetch remote commit — proceeding with file check")
+
+    # Clear the flag now; main.py must call ota.mark_ok() to re-set it
+    _clear_ok_flag()
+
+    success = _do_update(commit_sha)
+
+    if success:
+        info("OTA check complete — booting application")
+    else:
+        warn("OTA check had errors — booting with current files")
+
+    info("-" * 40)
+    gc.collect()

archive/ota_config.example.json

@@ -0,0 +1,9 @@
+{
+    "gitea_base": "http://git.baumann.gr",
+    "repo_owner": "adebaumann",
+    "repo_name": "Selsyn_inspired_gauge",
+    "repo_folder": "",
+    "repo_branch": "main",
+    "wifi_ssid": "YourNetwork",
+    "wifi_password": "YourPassword"
+}

archive/ota_manifest.txt

@@ -0,0 +1 @@
+*.py

changes.md

@@ -0,0 +1,46 @@
+# Changes
+
+## 2026-04-27 — Arduino firmware refactor (`Gaugecontroller/Gaugecontroller.ino`)
+
+### Non-blocking VFD multiplexer
+`vfd::refresh()` previously held each digit for 2000 µs via `delayMicroseconds`,
+which capped the effective stepper pulse rate at roughly 500 Hz regardless of
+`maxSpeed`. It now tracks `phaseStartMicros`/`phaseActive` and returns
+immediately while the digit is still being held; the main loop runs at
+microsecond cadence again and the configured `maxSpeed = 4000.0f` steps/s is
+actually achievable.
+
+### Fixed-buffer command parser (no more `String` heap churn)
+Replaced `String rxLine` with `char rxBuf[128]` and converted the entire
+command pipeline to take `const char*`:
+
+- `processLine`, `sendReply`, `vfd::parseCommand`
+- All `parse*` functions: `parseSet`, `parseSpeed`, `parseAccel`, `parseEnable`,
+  `parseZero`, `parseHome`, `parseSweep`, `parsePosQuery`, `parseCfgQuery`,
+  `parseLedQuery`, `parseLed`, `parseBlink`, `parseBreathe`, `parseDflash`,
+  `parseVfd`, `parsePing`.
+
+`parseSpeed` / `parseAccel` / `parseSweep` use `strncmp` + `atof` because the
+default AVR-libc `sscanf` doesn't support `%f`. No allocations on the command
+path; the Mega's heap no longer fragments over time.
+
+### Cached `ledNeedsSwap[TOTAL_LEDS]`
+Per-LED RGB-vs-GRB swap flag is now precomputed once in `setup()` from
+`gaugePins[].ledOrder`. `encodeForStrip` is a single array index instead of
+walking the gauge table on every LED read/write.
+
+### Cached step direction per gauge
+Added `Gauge.lastDir`. `setDir()` skips the DIR-pin `digitalWrite` when the
+direction hasn't flipped (the common case during a step run) and adds a 1 µs
+DIR-to-STEP setup delay only when it actually flips.
+
+### Cleanups
+- Removed the `absf` helper; use `fabsf` consistently.
+- Removed the `+ 0.0001f` epsilon in the trapezoidal braking-distance divisor.
+  `parseAccel` already rejects `accel <= 0`, so the divisor is always positive.
+- Fixed the `<r> <ig> <b>` typo to `<r> <g> <b>` in the protocol comment for
+  `DFLASH`.
+
+### Build verification
+`arduino-cli compile --fqbn arduino:avr:mega Gaugecontroller`:
+17758 B flash (6%), 1845 B SRAM (22%).

wiring.md

@@ -0,0 +1,278 @@
+# Wiring
+
+This document describes the wiring required for the current integrated system:
+
+- `Arduino Mega 2560`
+- `HV5812P` VFD driver
+- 4-digit VFD tube with decimal point and alarm bell
+- 3 stepper-driven gauges
+- WS2812B LEDs
+- ESP32 running `gauge.py` as the MQTT / Home Assistant bridge
+
+It is intentionally based on the code that is in the repository now:
+
+- [Gaugecontroller.ino](/home/adebaumann/development/arduino_gauge_controller/Gaugecontroller/Gaugecontroller.ino:1)
+- [gauge.py](/home/adebaumann/development/arduino_gauge_controller/gauge.py:1)
+
+## System Power
+
+You effectively have three power domains:
+
+1. `5V logic`
+   for the Arduino Mega logic, the HV5812 logic side, and usually the step/dir logic inputs
+2. `high voltage for the VFD`
+   for `HV5812P VPP` and the VFD segment/grid drive
+3. `motor / actuator power`
+   for the stepper gauges and their driver hardware
+
+Minimum common rule:
+
+- all logic grounds must be common
+
+That means these must share `GND`:
+
+- Arduino Mega `GND`
+- ESP32 `GND`
+- HV5812P logic `GND`
+- stepper driver logic `GND`
+- WS2812B `GND`
+
+The VFD high-voltage supply still references the same ground, but its high-voltage nodes must never be connected directly to Arduino or ESP32 GPIO pins.
+
+## Arduino Mega 2560
+
+Use the Mega as the central logic controller.
+
+Power:
+
+- `Mega 5V` <- regulated `5V` logic supply
+- `Mega GND` <- common logic ground
+
+Serial bridge to ESP32:
+
+- `Mega RX1` pin `19` <- `ESP32 TX` GPIO `17`
+- `Mega TX1` pin `18` -> voltage divider -> `ESP32 RX` GPIO `16`
+- `Mega GND` <-> `ESP32 GND`
+
+This matches the current code:
+
+- Arduino uses `Serial1` in [Gaugecontroller.ino](/home/adebaumann/development/arduino_gauge_controller/Gaugecontroller/Gaugecontroller.ino:12)
+- ESP32 uses `UART(1, tx=17, rx=16)` in [gauge.py](/home/adebaumann/development/arduino_gauge_controller/gauge.py:149)
+
+Because the Mega transmits `5V` logic and the ESP32 expects `3.3V` logic on RX, add a resistor divider on the `Mega TX1 -> ESP32 RX` line.
+
+Suggested simple divider:
+
+- `Mega TX1` -> `1 kOhm` resistor -> divider node
+- divider node -> `2 kOhm` resistor -> `GND`
+- divider node -> `ESP32 GPIO16 (RX)`
+
+That scales the Mega's `5V` TX signal to roughly `3.3V` for the ESP32 RX input.
+
+## VFD Control: Mega -> HV5812P
+
+These are the integrated pin assignments used by the merged controller:
+
+| Mega Pin | HV5812P Signal | Purpose |
+|---|---|---|
+| `D46` | `DATA IN / DIN` | serial data into HV5812P |
+| `D47` | `CLOCK / CLK` | shift clock |
+| `D48` | `STROBE / LATCH` | latch transfer |
+| `D49` | `BLANKING / OE` | output blanking |
+| `5V` | `VDD` | HV5812 logic supply |
+| `GND` | `GND` | common reference |
+| `VFD HV+` | `VPP` | HV5812 high-voltage rail |
+
+Important:
+
+- `VDD` is the low-voltage logic rail
+- `VPP` is the high-voltage output rail
+- do not connect Arduino `5V` to `VPP`
+
+## HV5812P -> VFD Tube
+
+The current output map is:
+
+| HV5812 Output | Tube Function |
+|---|---|
+| `HVOut1` | segment `A` |
+| `HVOut2` | segment `B` |
+| `HVOut3` | segment `C` |
+| `HVOut4` | segment `D` |
+| `HVOut5` | segment `E` |
+| `HVOut6` | segment `F` |
+| `HVOut7` | segment `G` |
+| `HVOut8` | decimal point segment |
+| `HVOut9` | alarm bell segment |
+| `HVOut10` | digit grid 1 |
+| `HVOut11` | digit grid 2 |
+| `HVOut12` | digit grid 3 |
+| `HVOut13` | digit grid 4 |
+| `HVOut14` | indicator grid between digits 2 and 3 |
+
+Logical segment layout:
+
+```text
+ ---A---
+|       |
+F       B
+|---G---|
+E       C
+|       |
+ ---D---
+```
+
+Additional VFD wiring notes:
+
+- the VFD filament/heater wiring is separate from the HV5812 outputs
+- the exact filament supply depends on your tube
+- the HV5812 only drives the segments and grids
+
+## Gauge Control Pins
+
+The current sketch drives three gauges.
+
+Each gauge needs a driver or actuator input that accepts:
+
+- `DIR`
+- `STEP`
+- optionally `ENABLE` if you later add one in code
+
+Current assignments:
+
+| Gauge | Mega DIR | Mega STEP |
+|---|---|---|
+| `Gauge 0` | `D50` | `D51` |
+| `Gauge 1` | `D8` | `D9` |
+| `Gauge 2` | `D52` | `D53` |
+
+Connect each pair to the matching stepper driver inputs.
+
+Example:
+
+- `Mega D50` -> Gauge 0 driver `DIR`
+- `Mega D51` -> Gauge 0 driver `STEP`
+- `Mega D8` -> Gauge 1 driver `DIR`
+- `Mega D9` -> Gauge 1 driver `STEP`
+- `Mega D52` -> Gauge 2 driver `DIR`
+- `Mega D53` -> Gauge 2 driver `STEP`
+
+Also connect:
+
+- `Mega GND` -> each driver logic ground
+
+If your driver boards need separate motor power, supply that from the proper motor supply. Do not power motors from the Mega `5V` pin.
+
+## WS2812 LED Strips
+
+The current sketch expects two LED data chains. Backlight and status LEDs stay
+on the main strip; the red/green dial indicator LEDs are on their own strip.
+
+| Mega Pin | LED Strip |
+|---|---|
+| `D22` | main backlight/status `DIN` |
+| `D36` | indicator `DIN` |
+| `5V` | both strips `5V` |
+| `GND` | both strips `GND` |
+
+Notes:
+
+- the command protocol still exposes `7 LEDs per gauge`
+- logical indices `0-2` are backlight, `3-4` are indicators, and `5-6` are status
+- use a proper 5V supply sized for the LED current
+- keep LED ground common with the Mega
+
+If the strip is powered from a separate 5V supply:
+
+- connect external `5V` -> LED `5V`
+- connect external `GND` -> LED `GND`
+- connect that same `GND` to `Mega GND`
+
+## ESP32 Bridge
+
+The ESP32 runs `gauge.py` and talks to the Mega over UART and to Home Assistant over MQTT/Wi-Fi.
+
+ESP32 to Mega:
+
+| ESP32 Pin | Mega Pin | Purpose |
+|---|---|---|
+| `GPIO17` | `RX1` pin `19` | ESP32 TX -> Mega RX |
+| `GPIO16` | `TX1` pin `18` | ESP32 RX <- Mega TX |
+| `GND` | `GND` | common ground |
+
+ESP32 power:
+
+- power the ESP32 from a proper `3.3V` or board-supported USB/5V input, depending on your board
+- do not feed raw `5V` into a bare `3.3V` ESP32 module unless the board has its own regulator
+
+## One-Page Wiring Summary
+
+### Power
+
+- `5V logic supply` -> Mega `5V`
+- `5V logic supply` -> HV5812 `VDD`
+- `5V logic supply` -> WS2812B `5V`
+- `motor supply` -> gauge driver motor power inputs
+- `VFD high-voltage supply` -> HV5812 `VPP`
+- all grounds common
+
+### Mega to ESP32
+
+- `Mega 19 (RX1)` <- `ESP32 GPIO17 (TX)`
+- `Mega 18 (TX1)` -> resistor divider -> `ESP32 GPIO16 (RX)`
+- `Mega GND` <-> `ESP32 GND`
+
+Resistor divider on `Mega TX1`:
+
+- `Mega TX1` -> `1 kOhm` -> divider node
+- divider node -> `ESP32 GPIO16`
+- divider node -> `2 kOhm` -> `GND`
+
+### Mega to HV5812
+
+- `D46` -> `DIN`
+- `D47` -> `CLK`
+- `D48` -> `STROBE`
+- `D49` -> `BLANKING`
+- `5V` -> `VDD`
+- `GND` -> `GND`
+- `VFD HV+` -> `VPP`
+
+### HV5812 to Tube
+
+- `HVOut1..7` -> segments `A..G`
+- `HVOut8` -> decimal point
+- `HVOut9` -> alarm bell
+- `HVOut10..13` -> digit grids `1..4`
+- `HVOut14` -> indicator grid
+
+### Mega to Gauges
+
+- `D50/D51` -> gauge 0 `DIR/STEP`
+- `D8/D9` -> gauge 1 `DIR/STEP`
+- `D52/D53` -> gauge 2 `DIR/STEP`
+
+### Mega to LEDs
+
+- `D22` -> WS2812B `DIN`
+- `5V` -> WS2812B `5V`
+- `GND` -> WS2812B `GND`
+
+## Sanity Checklist Before Power-On
+
+- Mega, ESP32, HV5812 logic, LED strip, and driver logic grounds are all common
+- Mega `D46-D49` go to the HV5812, not to the gauge drivers
+- Mega `D50-D53` and `D8-D9` go only to the gauge drivers
+- HV5812 `VDD` is `5V`
+- HV5812 `VPP` is the VFD high-voltage rail, not `5V`
+- ESP32 UART is crossed correctly: TX -> RX, RX -> TX
+- WS2812B has its own adequate 5V supply if current draw is significant
+- motor power is not coming from the Mega
+
+## What This Does Not Define
+
+This document does not define:
+
+- the exact VFD filament supply voltage/current
+- the exact motor driver board power pins, because that depends on the driver hardware you are using
+- the physical PDIP package pin numbers of the HV5812P