FutabaVFD

Arduino library for Futaba 8-digit and 16-digit VFD modules (M66004 controller, e.g. 8-MD-06INKM) on ESP32 via SPI.

Supports non-blocking horizontal scroll, split-flap single-digit animation, full-display flipIn/flipOut, and continuous vertical band — all driven from loop() without delay().

Author: Marc Staehli
License: MIT
Version: 3.0 (2026)

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Hardware

Signal	ESP32 pin	Notes
MOSI	23
SCK	18
CS	5	active LOW
MISO	19	16-digit only
RESET	19	8-digit only (same physical pin as MISO — different display)

Both modules use the same begin() call:

vfd.begin(/*SCLK*/ 18, /*MISO*/ 19, /*MOSI*/ 23, /*spiHz*/ 500000);

500 kHz SPI is recommended when using vertical animations.

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Installation

Copy the repository into your Arduino libraries folder:

FutabaVFD/
  library.properties
  README.md
  LICENSE
  src/
    FutabaVFD.h
    FutabaVFD.cpp
    FutabaVFD_Font5x7.h
  examples/
    APITest/APITest.ino
    ClockDemo/ClockDemo.ino
    FontTest/FontTest.ino
  pics/
    clockdemo.gif

Restart the Arduino IDE after copying. The examples will appear under File → Examples → FutabaVFD.

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Quick start

#include <FutabaVFD.h>

FutabaVFD vfd(16, /*CS*/ 5, /*RESET*/ -1);   // 16-digit
// FutabaVFD vfd(8, /*CS*/ 5, /*RESET*/ 19); // 8-digit

void setup() {
  vfd.begin(18, 19, 23, 500000);
  vfd.setBrightness(120);
  vfd.print("Hello!");
}

void loop() {
  vfd.update();   // must be called from loop()
}

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API reference

Lifecycle

FutabaVFD(uint8_t digits = 16, int8_t pinCS = SS,
           int8_t pinReset = -1, int spiBus = VSPI);

bool begin(int8_t sclk, int8_t miso, int8_t mosi,
           uint32_t spiHz = 100000, bool selfTest = false);
void end();
bool update();   // call every loop() iteration; returns true if display changed

selfTest counts 9→0 on all digits to verify wiring. Uses delay() internally — enable only during development.

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Direct writes

void    print(const char* s);                    // write at col 0, right-pad
void    writeChar(uint8_t col, char c);           // single character at column
void    writeString(uint8_t col, const char* s);  // write from col, truncate
void    clear();                                  // fill display with spaces
void    show();                                   // re-send display-lights-on
void    setBrightness(uint8_t level);             // 0 (dim) .. 255 (full)
void    standby(bool on);                         // power-save; DCRAM preserved
uint8_t digits() const;                           // returns 8 or 16

UTF-8 German umlauts (Ä Ö Ü ä ö ü) and degree sign (°) are translated automatically.

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Horizontal scroll

// Classic: text starts left-aligned, holds for holdMs, then scrolls left. Loops.
void scroll(const char* s, uint16_t speedMs = 200, uint16_t holdMs = 500);

// Ticker: enters from right edge, scrolls through continuously. Loops.
void ticker(const char* s, uint16_t speedMs = 150);

void stopScroll();
bool isScrolling() const;

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Blink

void blink(uint16_t periodMs);   // toggle display on/off every periodMs
void stopBlink();
bool isBlinking() const;

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Vertical: full display

// All characters in s drop in from above simultaneously.
// Returns false if s has more than 8 distinct characters (CGRAM limit).
bool flipIn(const char* s, uint16_t totalMs = 400);

// Current display slides out downward. Reads from internal shadow buffer.
bool flipOut(uint16_t totalMs = 400);

After flipIn completes, the result is committed as plain CGROM and CGRAM is freed.

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Vertical: single digit — split-flap

// Old character at col slides down; new one slides in from above.
// All other columns are completely unaffected.
// Always uses exactly 1 CGRAM slot — never exceeds the 8-slot budget.
void flip(uint8_t col, char newChar, uint16_t totalMs = 250);

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Vertical: endless rotating band

bool band(const char* s, uint16_t speedMs = 80, Direction dir = UP);
// dir: UP or DOWN

void stopVertical();
bool isAnimating() const;   // true if scroll or any vertical animation is active

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Font

Two built-in 5×7 pixel fonts are stored in flash (PROGMEM), one per display type. Selected automatically from the digits constructor parameter.

Array	Display
kAscii16[95][5]	16-digit
kAscii8[95][5]	8-digit

Coverage: ASCII 0x20–0x7E + Ä Ö Ü ä ö ü °. Both tables compile in at ~1900 bytes total.

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CGRAM budget

The M66004 has 8 CGRAM slots. flipIn and band need one slot per distinct character in the string.

Situation	Slots used
flip() single digit	always 1 — always safe
flipIn("12:34:56")	6 (1 2 3 4 5 6) — ok
flipIn("AAABBBCCC")	3 (A B C) — ok
flipIn("abcdefghi")	9 — fails, returns false

If flipIn returns false, reduce distinct characters or use scroll().

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Examples

APITest

Sequential test of every API call. Select display type at the top of the file with a single #define.

ClockDemo

hh:mm:ss clock seeded from compile time — no RTC needed. Only digits that actually change are animated with flip(), right-to-left. Works on both 8-digit and 16-digit displays. Select at top with #define.

SimpleFlipClock

hh:mm:ss clock seeded from compile time — no RTC needed. Beginner friendly variant of the "ClockDemo".

FontTest

Cycles through all 62 printable characters (0–9, A–Z, a–z) using flipIn and flipOut. Select display at top with #define.

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Notes

• update() must be called from loop() as often as possible. Never use delay() in your main loop when animation is active.
• The shadow buffer tracks DCRAM content internally. All direct writes update the shadow automatically, so flipOut and flip always know the current display state without DCRAM readback (the M66004 is write-only).
• flip() is always safe regardless of how many distinct characters are on the display.