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mangavalkandClaude Opus 5.5 37d5bcc1f8 Align docs with the EL512.256-H datasheet

The datasheet (docs/datasheet, Planar 020-0354-00A) is now stated as the
source of truth. Two-bit mode is PS1 jumper 2 (DCONFIG) removed
(Table 3), not a generic "mode jumper". The README timing table now lists
the Table 5/6 limits beside our values, and the notes add T1-T8, the
8 ns setup/hold from Figure 4 and the input levels from Table 4.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-10-05 21:13:36 +02:00

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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 a precomputed frame from DMA, so the CPU is free while the panel refreshes.

Status: framebuffer, GFX layer, row encoder and I2S/DMA refresh are implemented and build cleanly; the signal timing has not yet been checked on hardware. Updates are not yet tear-free.

Hardware

ESP-WROOM-32 dev board (esp32dev)
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	Function	ESP32 GPIO	DMA byte bit
VCLK	Video clock (rising edge)	18	I2S0 BCK
VID	Pixel data, even columns	19	0
TVID	Pixel data, odd columns (two-bit mode)	21	1
HS	Horizontal sync	22	2
VS	Vertical sync	23	3
ENABLE	Display enable	25	—
_LOWPWR	Low-power mode (active low)	26	—
GND	Ground	GND	—

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 (esp32dev, Arduino, Adafruit GFX)
include/pins.h        pin map
src/main.cpp          test sketch: test pattern + text
lib/EL512/            local library
  src/EL512Panel.*    framebuffer, row encoder, I2S DMA refresh
  src/EL512_GFX.*     Adafruit_GFX subclass
test/                 unit tests (placeholder)
docs/                 datasheet and notes

Build and flash

Requires PlatformIO (CLI or the VS Code extension).

pio run

pio run -t upload

pio device monitor

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.

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