# 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