Planar EL512.256-H on ESP32

Drive a Planar EL512.256-H (512 × 256, monochrome electroluminescent) panel from an ESP-WROOM-32 (classic ESP32), with an Adafruit GFX compatible driver so the usual drawing, text and font APIs work.

The panel has no frame memory and needs a continuous video stream. The ESP32's I2S0 peripheral in 8-bit parallel (LCD) mode streams it by DMA from a small ring of encoded lines that an interrupt keeps refilling (17 KB instead of a 142 KB full frame), so there is room left for Wi-Fi.

Status: runs on hardware with a correct, tear-free image (drawing goes into a back buffer that is swapped in at the start of a frame). Usable three ways: as an Arduino / PlatformIO library with Adafruit GFX, as an ESPHome display component for Home Assistant, and as the stand-alone Still Alive demo.

Hardware

• ESP32 board: a Wemos D1 mini ESP32 is used here (esp32dev in PlatformIO, wemos_d1_mini32 in ESPHome); pinout in docs/D1_mini_esp32_schema.jpg
• Planar EL512.256-H, configured for two-bit parallel mode: jumper 2 (DCONFIG) of pin strip PS1 removed, jumper 1 (SELFTST) fitted (datasheet Table 3)
• Datasheet: docs/datasheet/EL512.256-H3 FRB.pdf
• Check the panel's logic-level and supply requirements in the datasheet before wiring.

Wiring

Panel signal	Panel pin (Table 1)	Function	ESP32 GPIO	DMA byte bit
VCLK	J1-13	Video clock, data latched on rising edge	18	I2S0 BCK
VID	J1-15	Pixel data, even columns (x = 1, 3, …)	19	0
TVID	J1-7	Pixel data, odd columns (x = 0, 2, …)	21	1
HS	J1-11	Horizontal sync	22	2
VS	J1-9	Vertical sync (rising edge used)	23	3
ENABLE	J2-6	Display enable, low = off	25	—
_LOWPWR	J2-5	Low-power mode, low = on	26	—
GND	J1-6, 8, 10, 12, 14, 16	Signal return	GND	—

The datasheet numbers columns 1 to 512 from the left; x in the code is 0-based, so x = 0 is column 1 (odd, TVID).

Power (Table 1, Table 4): Vcc1 +5 V logic on J1-3, 4 (4.75–5.25 V, 0.2 A max); Vcc2 +11…+30 V on J1-1, 2 (0.9 A max at 12 V). J1-5 is reserved: do not connect.

The panel inputs are HCT compatible with internal pull-ups of unstated voltage, and the ESP32 is not 5 V tolerant, so drive them through a 74HCT245 or 74AHCT541 powered from 5 V (see the plan). ENABLE is pulled high inside the panel, so the panel scans while the ESP32 is still booting and VCLK is not running yet; add a pull-down (for example 10 kΩ) on the buffer's ENABLE input so the panel stays off until begin() starts the stream. Keep the cable under 300 mm, or add 47 Ω series resistors for up to 2 m.

With Wi-Fi on, the panel can blank for a moment when the ESP32 transmits (seen at page changes, which report the new page to Home Assistant). The refresh measured clean on the ESP32 side at those moments, so the signal is disturbed on the wires: connect all six J1 GND pins, run them along the signal wires, keep the antenna away from the cable, and preferably use the 5 V buffer above. Brief blanking during boot is expected until ENABLE has its pull-down.

The pin map lives in include/pins.h.

Timing

Parameter	Value	Datasheet limit (Tables 5, 6)
Pixel clock (VCLK)	5 MHz, 2 pixels per clock	30 MHz max, keep running
HS high (T7)	256 clocks	256 in two-bit mode, even
HS low (T6)	16 clocks	4 clocks min
HS period (T8)	272 clocks = 54.4 µs	50 µs min
Lines per frame	261 (256 visible + 5 blanking)	256 rows + T1
Front porch (T1)	220.8 µs (last row end to VS rise)	100 µs min
Refresh	5 MHz / (272 × 261) ≈ 70.4 Hz	70 Hz typ, 75 Hz max

The datasheet (docs/datasheet/) is the source of truth; if anything here disagrees with it, the datasheet wins.

Layout

platformio.ini          build config: envs still_alive (default) and esp32dev
include/pins.h          pin map
components/el512/       shared driver + ESPHome component (one copy of the code)
  el512_panel.*         framebuffer, DMA ring, refresh interrupt (ESP-IDF API)
  still_alive.*         Portal end-credits show, 5x7 font (el512_font.h)
  still_alive_data.h    show content, generated by tools/import_still_alive.py
  el512_display.*       ESPHome display platform `el512`
  __init__.py, display.py   ESPHome config schema
lib/EL512/              Arduino library: Adafruit_GFX front end (EL512_GFX)
src/still_alive/        Portal-style end-credits demo (env still_alive)
src/test_images/        test sketch: cycles through 12 test images (env esp32dev)
esphome/                el512-panel.yaml (Home Assistant display), el512-smoke.yaml
home_assistant/packages/  el512_panel.yaml: helper sensors for the ESPHome pages
tools/                  import_still_alive.py
test/                   unit tests (placeholder)
docs/                   datasheet and notes

Build and flash

Requires PlatformIO (CLI or the VS Code extension). The upload and monitor port is set to COM20 in platformio.ini.

pio run -e still_alive -t upload   # end-credits demo
pio run -e esp32dev -t upload      # test images
pio device monitor

ESPHome / Home Assistant

esphome/el512-panel.yaml turns the panel into a Home Assistant display with eight pages: clock and weather, forecast, agenda, a sensor dashboard with a message line, now playing, Plex, solar, and Still Alive. Pages rotate on an interval; Home Assistant gets a page select, a pause switch, the interval, a message text, a "Play Still Alive" button, and Display / Low power mode switches (ENABLE, _LOWPWR).

The component comes straight from this repository:

external_components:
  - source:
      type: git
      url: https://mangavalk.com/mangavalk/planar-EL512.256-H.git
      ref: main
    components: [el512]

display:
  - platform: el512
    id: panel
    enable_pin: GPIO25        # optional, J2-6
    low_power_pin: GPIO26     # optional, J2-5
    still_alive_page: page_still_alive   # optional
    pages: ...

Data pins default to the wiring above (vclk_pin, vid_pin, tvid_pin, hs_pin, vs_pin can be changed). Page lambdas can use helpers such as el512::split(), el512::weather_icon(), el512::fit() and el512::watts() (el512_helpers.h).

Setup:

1. Copy home_assistant/packages/el512_panel.yaml to /config/packages/ (with homeassistant: packages: !include_dir_named packages in configuration.yaml) and reload the template entities. It adds sensor.el512_forecast, sensor.el512_agenda, sensor.el512_now_playing and sensor.el512_plex_streams.
2. Put el512-panel.yaml in the ESPHome add-on and add el512_api_key and el512_ota_password to its secrets.yaml. The entity IDs at the top (substitutions) and in the sensor list are this installation's; adjust them.
3. Flash once over USB (or use ESPHome's web installer), then add the device in Home Assistant; later updates go wirelessly from the add-on.

The component logs a warning when the ESP32 side of the refresh has a problem (DMA FIFO underrun, late ring refill, swap timeout); otherwise a debug summary once a minute.

For local builds, esphome/el512-panel-local.yaml (git-ignored) is the same config with source: {type: local, path: ../components}; build it with the ESPHome CLI from PowerShell or cmd (the ESP-IDF installer refuses to run under Git Bash/MSYS).

Still Alive demo

A recreation of Portal's ending: timed song text typed into a console on the left, credits scrolling top right, ASCII art bottom right. The same show runs as the PlatformIO demo and as a page in ESPHome. The text, timing, art and credits in components/el512/still_alive_data.h come from SDSkyKlouD/still-alive-web and can be regenerated with:

python tools/import_still_alive.py   # stops after the credits text (--until-ms 200000)
pio run -e still_alive -t upload

Start the song when the serial log says: 7.75 s after reset in the PlatformIO demo, or 7.75 s after the Still Alive page is shown in ESPHome.

Disclaimer: "Still Alive" was written by Jonathan Coulton for Portal (2007). Portal, its credits and ASCII art are © Valve Corporation (see Valve Legal Info); the web recreation they are imported from is by SD SkyKlouD. They are included only for personal, non-commercial use in this hobby project, and all rights remain with their owners. This project is not affiliated with or endorsed by Valve.

Using the driver

#include <EL512.h>
#include "pins.h"

EL512Panel panel({el512pins::VCLK, el512pins::VID, el512pins::TVID, el512pins::HS,
                  el512pins::VS, el512pins::ENABLE, el512pins::LOWPWR_N});
EL512_GFX display(panel);

void setup() {
  display.begin();
  display.setTextColor(1);
  display.print("Hello");
  display.display();   // push the drawing buffer to the refresh stream
}

See docs/README.md for design notes and the plan.