# Samsung serial VFD — ESPHome component

An ESPHome external component for the Samsung 2-line × 20-character serial VFD
(vacuum fluorescent display) that takes 5 V TTL serial at 9600 baud, 8N1.

It keeps a copy of the screen in RAM and only sends data when something
changes. Updates overwrite the screen in place instead of clearing it first,
so the clock doesn't flicker.

```
components/samsung_vfd/   the component (Python schema + C++)
examples/samsung-vfd.yaml full example: clock + two Home Assistant text entities
examples/secrets.yaml.example
```

## Using it from your ESPHome server

Add this to your device YAML. ESPHome fetches the component from git when it
compiles.

```yaml
external_components:
  - source: github://REPO_OWNER/REPO_NAME@main
    components: [samsung_vfd]
    refresh: 1d

uart:
  id: uart_vfd
  tx_pin: GPIO17
  baud_rate: 9600

time:            # needed by the component (used by samsung_vfd.printf)
  - platform: sntp
    id: sntp_time

samsung_vfd:
  id: vfd
  uart_id: uart_vfd
```

For a complete device, copy [examples/samsung-vfd.yaml](examples/samsung-vfd.yaml)
into your ESPHome config folder. Add the keys from
[examples/secrets.yaml.example](examples/secrets.yaml.example) to your
`secrets.yaml`.

## Wiring

The component only sends to the display. The ESP32's 3.3 V output is enough for
most 5 V TTL inputs. ESP32 GPIOs are **not** 5 V tolerant, so never connect the
display's TX back to the ESP32 without a level shifter or divider.

| Display | ESP32 |
|---------|-------|
| RX      | GPIO17 (UART TX) |
| GND     | GND |
| 5 V     | external 5 V supply |

The display draws more current than a dev-board regulator can comfortably
supply. Power it from its own supply and connect the grounds together.

To use GPIO1 (TX0, shared with USB logging), set `tx_pin: GPIO1` and
`logger: baud_rate: 0` so log output doesn't end up on the display. If the
display stays blank at 3.3 V levels, add a 74HCT125 or similar level shifter.

## Configuration

```yaml
samsung_vfd:
  id: vfd
  uart_id: uart_vfd
  cols: 20              # default 20 (1–80)
  rows: 2               # default 2 (1–8)
  send_newlines: false  # default false; send CR LF between lines
```

The UART must be 9600 baud with a `tx_pin`. The component requires a `time:`
component in the config.

## Actions

| Action | Options |
|--------|---------|
| `samsung_vfd.print` | `text` (templatable). Optional `line:` (0-based) replaces one line. Without `line:`, the text is word-wrapped over the whole screen; `\n` forces a new line. Optional `centered: true`. |
| `samsung_vfd.printf` | Shows the current time formatted with strftime, e.g. `format: "%H:%M:%S"`. Requires `time_id:`. Takes the same `line:` and `centered:` options. Does nothing until the clock has synced. |
| `samsung_vfd.clear` | Clears the screen. |
| `samsung_vfd.home` | Moves the cursor home. |

```yaml
- samsung_vfd.print:
    id: vfd
    line: 0
    text: !lambda 'return "Temp " + to_string((int) id(temp).state) + " C";'
- samsung_vfd.printf:
    id: vfd
    time_id: sntp_time
    line: 1
    centered: true
    format: "%a %d %b %H:%M"
```

From a lambda you can call `id(vfd).print(...)`, `print_line(line, text, centered)`,
`clear()`, `home()` and `line_text(line)`.

Text is converted to one byte per character. Accented Latin-1 letters lose
their accent (é → e), other non-ASCII characters become `?`, and control
characters become spaces.

## What the example config does

- On boot: clears the screen, shows `Hello World!` for 3 s, then restores line 1.
- Bottom line: a live clock, `%a %d %b  %H:%M:%S`, updated every second (SNTP,
  Europe/Amsterdam).
- Two Home Assistant `text` entities:
  - **VFD line 1** (max 20 chars) is shown on the top line and kept across
    reboots.
  - **VFD status** (max 40 chars) shows a full-screen, word-wrapped, centred
    banner for 10 s. The clock pauses meanwhile, then line 1 and the clock come
    back.
- Wi-Fi with a captive-portal fallback AP, OTA updates and an encrypted native
  API.

## Protocol

| Bytes | Effect |
|-------|--------|
| `1B 40` (`ESC @`) | init / reset |
| `0C` | clear screen |
| `0B` | cursor home |
| text | printed at the cursor; wraps to the next line by itself |

Each update sends `0B` (home) followed by both lines, each padded to exactly
`cols` characters.

## Troubleshooting

- **Line 2 lands on the wrong row, or text runs together:** try
  `send_newlines: true`.
- **The screen scrolls up a line after each update:** the display scrolls as
  soon as the last cell is written. Use `cols: 19` together with
  `send_newlines: true`.
- **A stray character appears top-left:** the display doesn't treat `0B` as
  home. Change `CMD_HOME` in
  [samsung_vfd.h](components/samsung_vfd/samsung_vfd.h).
- **Garbled characters:** check that `uart:` is at 9600 baud and that the
  display takes 5 V TTL levels, not RS-232 levels. A real RS-232 input needs a
  MAX232 inverter.