CFG? added

Gaugecontroller/Gaugecontroller.ino

@@ -258,7 +258,7 @@ struct Gauge {
   long homingBackoffSteps = 3800; // Deliberately a touch past full reverse travel.
 
   float velocity = 0.0f;
-  float maxSpeed = 5000.0f;
+  float maxSpeed = 4000.0f;
   float accel = 6000.0f;
   float homingSpeed = 500.0f;
 
@@ -794,6 +794,24 @@ bool parsePosQuery(const String& line) {
   return false;
 }
 
+// Answers `CFG?` with speed and acceleration for every gauge.
+// Emits one `CFG <id> <maxSpeed> <accel>` line per gauge, then replies `OK`.
+bool parseCfgQuery(const String& line) {
+  if (line == "CFG?") {
+    for (uint8_t i = 0; i < GAUGE_COUNT; i++) {
+      CMD_PORT.print("CFG ");
+      CMD_PORT.print(i);
+      CMD_PORT.print(' ');
+      CMD_PORT.print((int)gauges[i].maxSpeed);
+      CMD_PORT.print(' ');
+      CMD_PORT.println((int)gauges[i].accel);
+    }
+    sendReply("OK");
+    return true;
+  }
+  return false;
+}
+
 // Answers the mandatory life question: are you there?
 // Reply: `PONG`.
 bool parsePing(const String& line) {
@@ -1058,6 +1076,7 @@ void processLine(const String& line) {
   if (parseHome(line)) return;
   if (parseSweep(line)) return;
   if (parsePosQuery(line)) return;
+  if (parseCfgQuery(line)) return;
   if (parseLedQuery(line)) return;
   if (parseLed(line)) return;
   if (parseBlink(line)) return;

README.md

@@ -1,3 +1,91 @@
 # 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
+- `gauge.py`: the ESP32 / MicroPython MQTT bridge that exposes the controller to Home Assistant
+
+## 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 Entities
+
+The MQTT bridge publishes Home Assistant discovery entities for the VFD:
+
+- `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
+
+## MQTT Topics
+
+Using the configured `mqtt_prefix` from `config.json`, the VFD topics are:
+
+- `<prefix>/vfd/set`
+- `<prefix>/vfd/state`
+- `<prefix>/vfd/decimal_point/set`
+- `<prefix>/vfd/decimal_point/state`
+- `<prefix>/vfd/alarm/set`
+- `<prefix>/vfd/alarm/state`
+
+Example with the default prefix `gauges`:
+
+- `gauges/vfd/set`
+- `gauges/vfd/decimal_point/set`
+- `gauges/vfd/alarm/set`
+
+Example payloads:
+
+- publish `0123` to `gauges/vfd/set`
+- publish `ON` to `gauges/vfd/decimal_point/set`
+- publish `OFF` to `gauges/vfd/alarm/set`
+
+The MQTT bridge then converts that into the correct Arduino serial command such as `VFD 0123.`.

Rewire_checklist.md

@@ -0,0 +1,322 @@
+# 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 WS2812B LEDs
+
+Connect:
+
+- `Mega D22` -> `WS2812B DIN`
+- `5V LED supply` -> `WS2812B 5V`
+- `WS2812B GND` -> 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 +1,413 @@
+# 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` -> `WS2812 DIN`
+- `5V` -> `WS2812 5V`
+- `GND` -> `WS2812 GND`
+
+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.

gauge.py

@@ -28,6 +28,16 @@ import gc
 from umqtt.robust import MQTTClient
 from machine import UART
 
+# Activate WiFi driver before any heavy heap allocation so it can claim its
+# contiguous DRAM block before the Python heap fragments the address space.
+# Only activate if not already running (e.g. boot.py may have started it).
+gc.collect()
+_early_wlan = network.WLAN(network.STA_IF)
+if not _early_wlan.active():
+    _early_wlan.active(True)
+del _early_wlan
+gc.collect()
+
 # ---------------------------------------------------------------------------
 # Logging
 # ---------------------------------------------------------------------------
@@ -293,6 +303,34 @@ _status_red_effect  = [None] * num_gauges
 _status_green_effect= [None] * num_gauges
 _bl_effect          = [None] * num_gauges
 
+vfd_text = ""
+vfd_decimal_point = False
+vfd_alarm = False
+
+
+def _build_vfd_command():
+    suffix = ""
+    if vfd_decimal_point:
+        suffix += "."
+    if vfd_alarm:
+        suffix += "!"
+
+    if vfd_text:
+        return f"VFD {vfd_text}{suffix}"
+    if suffix:
+        return f"VFD 0{suffix}"
+    return "VFD"
+
+
+def send_vfd_state():
+    arduino_send(_build_vfd_command())
+
+
+def publish_vfd_state(client):
+    client.publish(vfd_topics["state"], vfd_text, retain=True)
+    client.publish(vfd_topics["decimal_point_state"], b"ON" if vfd_decimal_point else b"OFF", retain=True)
+    client.publish(vfd_topics["alarm_state"], b"ON" if vfd_alarm else b"OFF", retain=True)
+
 
 def _backlight_changed(gauge_idx, new_color, new_on, new_brightness):
     return (
@@ -356,6 +394,53 @@ def publish_backlight_states(client):
             log_err(f"Backlight state publish failed for gauge {i}: {e}")
 
 
+def restore_backlight_state(gauge_idx, payload):
+    """Restore retained backlight state without republishing it back to MQTT."""
+    global backlight_color, backlight_brightness, backlight_on, _bl_effect
+
+    try:
+        data = ujson.loads(payload)
+    except Exception as e:
+        warn(f"Invalid retained backlight state for gauge {gauge_idx}: '{payload}' ({e})")
+        return
+
+    state_on = data.get("state", "OFF").upper() != "OFF"
+    effect = data.get("effect")
+    if effect not in _EFFECTS:
+        effect = None
+
+    if not state_on:
+        _bl_effect[gauge_idx] = None
+        backlight_on[gauge_idx] = False
+        set_backlight_brightness(gauge_idx, 0)
+        return
+
+    color = data.get("color", {})
+    r = max(0, min(255, int(color.get("r", backlight_color[gauge_idx][0]))))
+    g = max(0, min(255, int(color.get("g", backlight_color[gauge_idx][1]))))
+    b = max(0, min(255, int(color.get("b", backlight_color[gauge_idx][2]))))
+    raw_br = data.get("brightness", None)
+    if raw_br is not None:
+        brightness = max(0, min(100, round(int(raw_br) / 2.55)))
+    elif backlight_brightness[gauge_idx] > 0:
+        brightness = backlight_brightness[gauge_idx]
+    else:
+        brightness = 100
+
+    _bl_effect[gauge_idx] = effect
+    if effect:
+        scale = brightness / 100
+        rs = int(r * scale)
+        gs = int(g * scale)
+        bs_ = int(b * scale)
+        _send_effect(gauge_idx, _LED_BACKLIGHT_RANGE, (rs, gs, bs_), effect)
+        backlight_color[gauge_idx] = (r, g, b)
+        backlight_brightness[gauge_idx] = brightness
+        backlight_on[gauge_idx] = True
+    else:
+        set_backlight_color(gauge_idx, r, g, b, brightness)
+
+
 def _flush_backlight_state():
     global _bl_dirty_since
     if _bl_dirty_since is None:
@@ -419,6 +504,18 @@ def make_gauge_topics(prefix, gauge_id):
 
 gauge_topics = [make_gauge_topics(MQTT_PREFIX, g["id"]) for g in gauges]
 
+vfd_topics = {
+    "set": f"{MQTT_PREFIX}/vfd/set",
+    "state": f"{MQTT_PREFIX}/vfd/state",
+    "disc": f"homeassistant/text/{MQTT_CLIENT_ID}_vfd/config",
+    "decimal_point": f"{MQTT_PREFIX}/vfd/decimal_point/set",
+    "decimal_point_state": f"{MQTT_PREFIX}/vfd/decimal_point/state",
+    "decimal_point_disc": f"homeassistant/switch/{MQTT_CLIENT_ID}_vfd_decimal_point/config",
+    "alarm": f"{MQTT_PREFIX}/vfd/alarm/set",
+    "alarm_state": f"{MQTT_PREFIX}/vfd/alarm/state",
+    "alarm_disc": f"homeassistant/switch/{MQTT_CLIENT_ID}_vfd_alarm/config",
+}
+
 T_SET = f"{MQTT_PREFIX}/set"
 T_ZERO = f"{MQTT_PREFIX}/zero"
 
@@ -437,32 +534,56 @@ _DEVICE = {
 _wifi_check_interval_ms = 30000
 _last_wifi_check = 0
 _wifi_sta = None
+_WIFI_CONNECT_ATTEMPTS = 3
 
 
-def connect_wifi(ssid, password, timeout_s=15):
+def _reset_wifi_interface():
     global _wifi_sta
     _wifi_sta = network.WLAN(network.STA_IF)
+    if _wifi_sta.active():
+        _wifi_sta.active(False)
+        utime.sleep_ms(200)
     _wifi_sta.active(True)
-    if _wifi_sta.isconnected():
+    utime.sleep_ms(500)
+
+
+def connect_wifi(ssid, password, timeout_s=15, force_reconnect=False):
+    global _wifi_sta
+    _wifi_sta = network.WLAN(network.STA_IF)
+
+    if _wifi_sta.isconnected() and not force_reconnect:
         ip, mask, gw, dns = _wifi_sta.ifconfig()
         info("WiFi already connected")
         info(f"  IP:{ip}  mask:{mask}  gw:{gw}  dns:{dns}")
+        utime.sleep_ms(250)
         return ip
-    info(f"WiFi connecting to '{ssid}' ...")
-    _wifi_sta.connect(ssid, password)
-    deadline = utime.time() + timeout_s
-    while not _wifi_sta.isconnected():
-        if utime.time() > deadline:
-            log_err(f"WiFi connect timeout after {timeout_s}s")
-            raise OSError("WiFi connect timeout")
-        utime.sleep_ms(200)
-    ip, mask, gw, dns = _wifi_sta.ifconfig()
-    mac = ":".join(f"{b:02x}" for b in _wifi_sta.config("mac"))
-    info("WiFi connected!")
-    info(f"  SSID    : {ssid}")
-    info(f"  MAC     : {mac}")
-    info(f"  IP      : {ip}  mask:{mask}  gw:{gw}  dns:{dns}")
-    return ip
+
+    last_error = None
+    for attempt in range(_WIFI_CONNECT_ATTEMPTS):
+        info(f"WiFi connecting to '{ssid}' (attempt {attempt + 1}/{_WIFI_CONNECT_ATTEMPTS}) ...")
+        _reset_wifi_interface()
+        try:
+            _wifi_sta.connect(ssid, password)
+            deadline = utime.time() + timeout_s
+            while not _wifi_sta.isconnected():
+                if utime.time() > deadline:
+                    raise OSError("WiFi connect timeout")
+                utime.sleep_ms(250)
+
+            ip, mask, gw, dns = _wifi_sta.ifconfig()
+            mac = ":".join(f"{b:02x}" for b in _wifi_sta.config("mac"))
+            info("WiFi connected!")
+            info(f"  SSID    : {ssid}")
+            info(f"  MAC     : {mac}")
+            info(f"  IP      : {ip}  mask:{mask}  gw:{gw}  dns:{dns}")
+            utime.sleep_ms(500)
+            return ip
+        except Exception as e:
+            last_error = e
+            log_err(f"WiFi connect attempt {attempt + 1} failed: {e}")
+            utime.sleep_ms(1000)
+
+    raise last_error
 
 
 def check_wifi():
@@ -480,15 +601,7 @@ def check_wifi():
 
     log_err("WiFi lost connection — attempting reconnect...")
     try:
-        _wifi_sta.active(True)
-        _wifi_sta.connect(WIFI_SSID, WIFI_PASSWORD)
-        deadline = utime.time() + 15
-        while not _wifi_sta.isconnected():
-            if utime.time() > deadline:
-                log_err("WiFi reconnect timeout")
-                return
-            utime.sleep_ms(200)
-        ip, mask, gw, dns = _wifi_sta.ifconfig()
+        ip = connect_wifi(WIFI_SSID, WIFI_PASSWORD, timeout_s=15, force_reconnect=True)
         info(f"WiFi reconnected! IP:{ip}")
     except Exception as e:
         log_err(f"WiFi reconnect failed: {e}")
@@ -500,13 +613,41 @@ def check_wifi():
 
 
 def on_message(topic, payload):
+    global vfd_text, vfd_decimal_point, vfd_alarm
+
     if client_ref is None:
         return
     topic = topic.decode()
     payload = payload.decode().strip()
     info(f"MQTT rx  {topic}  {payload}")
 
+    if topic == vfd_topics["set"]:
+        vfd_text = payload.upper()
+        send_vfd_state()
+        publish_vfd_state(client_ref)
+        info(f"VFD text -> {vfd_text}")
+        return
+
+    if topic == vfd_topics["decimal_point"]:
+        vfd_decimal_point = payload.upper() == "ON"
+        send_vfd_state()
+        publish_vfd_state(client_ref)
+        info(f"VFD decimal point -> {'ON' if vfd_decimal_point else 'OFF'}")
+        return
+
+    if topic == vfd_topics["alarm"]:
+        vfd_alarm = payload.upper() == "ON"
+        send_vfd_state()
+        publish_vfd_state(client_ref)
+        info(f"VFD alarm -> {'ON' if vfd_alarm else 'OFF'}")
+        return
+
     for i, gt in enumerate(gauge_topics):
+        if topic == gt["led_bl_state"]:
+            restore_backlight_state(i, payload)
+            info(f"Gauge {i} backlight state restored")
+            return
+
         if topic == gt["zero"]:
             info(f"Home command received for gauge {i}")
             gauge_home(i)
@@ -723,6 +864,9 @@ def on_message(topic, payload):
 def _subscribe_all(c):
     c.subscribe(f"{MQTT_PREFIX}/set")
     c.subscribe(f"{MQTT_PREFIX}/zero")
+    c.subscribe(vfd_topics["set"])
+    c.subscribe(vfd_topics["decimal_point"])
+    c.subscribe(vfd_topics["alarm"])
     for i in range(num_gauges):
         prefix = f"{MQTT_PREFIX}/gauge{i}"
         c.subscribe(f"{prefix}/set")
@@ -732,6 +876,7 @@ def _subscribe_all(c):
         c.subscribe(f"{prefix}/led/red/set")
         c.subscribe(f"{prefix}/led/green/set")
         c.subscribe(f"{prefix}/led/backlight/set")
+        c.subscribe(f"{prefix}/led/backlight/state")
         c.subscribe(f"{prefix}/status_led/red/set")
         c.subscribe(f"{prefix}/status_led/green/set")
 
@@ -739,19 +884,42 @@ def _subscribe_all(c):
 def connect_mqtt():
     global client_ref, _mqtt_connected
     info(f"Connecting to MQTT broker {MQTT_BROKER}:{MQTT_PORT} ...")
-    client = MQTTClient(
-        client_id=MQTT_CLIENT_ID,
-        server=MQTT_BROKER,
-        port=MQTT_PORT,
-        user=MQTT_USER,
-        password=MQTT_PASSWORD,
-        keepalive=30,
-    )
-    client.set_callback(on_message)
-    client.connect()
-    client_ref = client
-    _mqtt_connected = True
-    info(f"MQTT connected  client_id={MQTT_CLIENT_ID}")
+    last_error = None
+    for attempt in range(3):
+        gc.collect()
+        try:
+            if client_ref is not None:
+                try:
+                    client_ref.disconnect()
+                except Exception:
+                    pass
+
+            client = MQTTClient(
+                client_id=MQTT_CLIENT_ID,
+                server=MQTT_BROKER,
+                port=MQTT_PORT,
+                user=MQTT_USER,
+                password=MQTT_PASSWORD,
+                keepalive=30,
+            )
+            client.set_callback(on_message)
+            client.connect()
+            client_ref = client
+            _mqtt_connected = True
+            info(f"MQTT connected  client_id={MQTT_CLIENT_ID}")
+            return
+        except Exception as e:
+            last_error = e
+            log_err(f"MQTT connect attempt {attempt + 1} failed: {type(e).__name__}: {e}")
+            try:
+                client.sock.close()
+            except Exception:
+                pass
+            gc.collect()
+            utime.sleep_ms(1000)
+
+    _mqtt_connected = False
+    raise last_error
 
 
 _mqtt_check_interval_ms = 30000
@@ -759,7 +927,20 @@ _last_mqtt_check = 0
 _discovery_queue = []
 _discovery_idx = 0
 _last_discovery_ms = 0
-_DISCOVERY_INTERVAL_MS = 200
+_DISCOVERY_INTERVAL_MS = 350
+
+
+def _compact_discovery_payload(payload):
+    """Trim optional HA discovery fields when RAM is tight."""
+    compact = dict(payload)
+
+    # Light entities are the largest payloads because they repeat effect metadata.
+    # Keep core functionality, but omit optional effect declarations to reduce heap use.
+    if compact.get("schema") == "json":
+        compact.pop("effect", None)
+        compact.pop("effect_list", None)
+
+    return compact
 
 
 def check_mqtt():
@@ -803,6 +984,11 @@ def check_mqtt():
             return True
         except Exception as e2:
             log_err(f"MQTT reconnect attempt {attempt + 1} failed: {e2}")
+            try:
+                client_ref.sock.close()
+            except Exception:
+                pass
+            gc.collect()
             utime.sleep_ms(2000)
 
     log_err("MQTT reconnection failed after 3 attempts")
@@ -810,7 +996,8 @@ def check_mqtt():
 
 
 def _publish_discovery_entity(client, topic, payload, log_msg):
-    client.publish(topic, ujson.dumps(payload), retain=True)
+    gc.collect()
+    client.publish(topic, ujson.dumps(_compact_discovery_payload(payload)), retain=True)
     info(log_msg)
 
 
@@ -995,6 +1182,58 @@ def _append_backlight_status_discovery(entries, dev_ref):
         )
 
 
+def _append_vfd_discovery(entries, dev_ref):
+    entries.append(
+        (
+            vfd_topics["disc"],
+            {
+                "name": "VFD Display",
+                "unique_id": f"{MQTT_CLIENT_ID}_vfd",
+                "cmd_t": vfd_topics["set"],
+                "stat_t": vfd_topics["state"],
+                "avty_t": gauge_topics[0]["status"],
+                "icon": "mdi:alpha-box",
+                "dev": dev_ref,
+            },
+            "Discovery: VFD text",
+        )
+    )
+    entries.append(
+        (
+            vfd_topics["decimal_point_disc"],
+            {
+                "name": "VFD Decimal Point",
+                "unique_id": f"{MQTT_CLIENT_ID}_vfd_decimal_point",
+                "cmd_t": vfd_topics["decimal_point"],
+                "stat_t": vfd_topics["decimal_point_state"],
+                "avty_t": gauge_topics[0]["status"],
+                "pl_on": "ON",
+                "pl_off": "OFF",
+                "icon": "mdi:circle-small",
+                "dev": dev_ref,
+            },
+            "Discovery: VFD decimal point",
+        )
+    )
+    entries.append(
+        (
+            vfd_topics["alarm_disc"],
+            {
+                "name": "VFD Alarm",
+                "unique_id": f"{MQTT_CLIENT_ID}_vfd_alarm",
+                "cmd_t": vfd_topics["alarm"],
+                "stat_t": vfd_topics["alarm_state"],
+                "avty_t": gauge_topics[0]["status"],
+                "pl_on": "ON",
+                "pl_off": "OFF",
+                "icon": "mdi:alarm-bell",
+                "dev": dev_ref,
+            },
+            "Discovery: VFD alarm",
+        )
+    )
+
+
 def schedule_discovery():
     global _discovery_queue, _discovery_idx, _last_discovery_ms
     _dev_ref = _DEVICE
@@ -1005,6 +1244,7 @@ def schedule_discovery():
     _append_acceleration_discovery(entries, _dev_ref)
     _append_indicator_led_discovery(entries, _dev_ref)
     _append_backlight_status_discovery(entries, _dev_ref)
+    _append_vfd_discovery(entries, _dev_ref)
     _discovery_queue = entries
     _discovery_idx = 0
     _last_discovery_ms = 0
@@ -1030,15 +1270,18 @@ def service_discovery():
     if _last_discovery_ms and utime.ticks_diff(now, _last_discovery_ms) < _DISCOVERY_INTERVAL_MS:
         return
 
+    gc.collect()
     topic, payload, log_msg = _discovery_queue[_discovery_idx]
-    if isinstance(payload, bytes):
-        client_ref.publish(topic, payload, retain=True)
-    else:
-        _publish_discovery_entity(client_ref, topic, payload, log_msg)
+    try:
+        if isinstance(payload, bytes):
+            client_ref.publish(topic, payload, retain=True)
+        else:
+            _publish_discovery_entity(client_ref, topic, payload, log_msg)
+    except Exception as e:
+        log_err(f"Discovery publish failed for {topic}: {e}")
     _discovery_idx += 1
     _last_discovery_ms = utime.ticks_ms()
-    if (_discovery_idx & 3) == 0:
-        gc.collect()
+    gc.collect()
 
 
 def publish_online(client):
@@ -1052,12 +1295,14 @@ def publish_state(client):
         client.publish(gt["state"], str(gauge_targets[i]))
         client.publish(gt["speed_state"], str(gauge_speeds[i]), retain=True)
         client.publish(gt["acceleration_state"], str(gauge_accelerations[i]), retain=True)
+    publish_vfd_state(client)
 
 
 def apply_motion_defaults():
     for i in range(num_gauges):
         gauge_set_speed(i, gauge_speeds[i])
         gauge_set_acceleration(i, gauge_accelerations[i])
+    send_vfd_state()
 
 
 # ---------------------------------------------------------------------------
@@ -1066,13 +1311,30 @@ def apply_motion_defaults():
 
 
 def main():
+    gc.collect()
     info("=" * 48)
     info("Gauge MQTT controller starting")
+    info(f"Heap free: {gc.mem_free()} bytes")
     info("=" * 48)
 
-    connect_wifi(WIFI_SSID, WIFI_PASSWORD)
+    gc.collect()
+    connect_wifi(WIFI_SSID, WIFI_PASSWORD, force_reconnect=True)
 
-    connect_mqtt()
+    mqtt_attempts = 0
+    while True:
+        try:
+            connect_mqtt()
+            break
+        except Exception as e:
+            mqtt_attempts += 1
+            log_err(f"MQTT connect failed: {e} (attempt {mqtt_attempts})")
+            if mqtt_attempts % 3 == 0:
+                log_err("WiFi may be stale — forcing reconnect...")
+                try:
+                    connect_wifi(WIFI_SSID, WIFI_PASSWORD, force_reconnect=True)
+                except Exception as we:
+                    log_err(f"WiFi reconnect failed: {we}")
+            utime.sleep_ms(5000)
     _subscribe_all(client_ref)
     schedule_discovery()
 

wiring.md

@@ -0,0 +1,275 @@
+# 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.
+
+## WS2812B LED Strip
+
+The current sketch expects one shared WS2812B chain.
+
+| Mega Pin | WS2812B |
+|---|---|
+| `D22` | `DIN` |
+| `5V` | `5V` |
+| `GND` | `GND` |
+
+Notes:
+
+- the code expects `7 LEDs per gauge`, so `21 LEDs total`
+- 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