# 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.