Futaba 8-MD-06INK VFD Display Driver

ESP-IDF driver for the Futaba 8-MD-06INK Vacuum Fluorescent Display (VFD) module. This 8-digit VFD display communicates via SPI and supports customizable characters and brightness control.

Features

• 8-digit alphanumeric display support
• SPI communication (up to 500 kHz)
• Adjustable brightness (dimming) control
• Custom character definition (CGRAM)
• Decimal point control for each digit
• Standby mode for power saving
• Direct segment control

Hardware Connection

VFD Pin	ESP32 Pin	Description
VCC	3.3V/5V	Power supply
GND	GND	Ground
DIN	MOSI	SPI Data In
CLK	SCLK	SPI Clock
CS	GPIO (CS)	Chip Select (Active Low)
RST	GPIO (RST)	Reset (Optional)

Note: The SPI interface uses LSB-first bit order with CPOL=1, CPHA=1 (SPI Mode 3).

Installation

Using ESP Component Registry (Recommended)

idf.py add-dependency "ftb-8-md"

Manual Installation

Copy the ftb-8-md folder to your project's components directory.

Quick Start

#include "ftb-8-md.h"
#include "driver/spi_master.h"

void app_main(void)
{
    // Initialize SPI bus
    spi_bus_config_t bus_cfg = {
        .mosi_io_num = GPIO_NUM_23,
        .miso_io_num = -1,
        .sclk_io_num = GPIO_NUM_18,
        .quadwp_io_num = -1,
        .quadhd_io_num = -1,
        .max_transfer_sz = 32,
    };
    spi_bus_initialize(SPI2_HOST, &bus_cfg, SPI_DMA_CH_AUTO);

    // Register VFD device
    spi_device_handle_t vfd = ftb8md_device_register(
        SPI2_HOST,
        GPIO_NUM_5,   // CS pin
        GPIO_NUM_4    // Reset pin (use -1 if not connected)
    );

    if (vfd != NULL) {
        // Display a string
        ftb8md_show_string(vfd, 0, "HELLO   ");
        
        // Set brightness (0-240)
        ftb8md_set_dimming(vfd, 120);
        
        // Turn on decimal point at digit 3
        ftb8md_set_dot(vfd, 3, true);
    }
}

API Reference

Initialization

ftb8md_device_register()

spi_device_handle_t ftb8md_device_register(spi_host_device_t host_id, int cs_pin, int reset_pin);

Register and initialize the VFD display device on the SPI bus.

Parameters:

• host_id: SPI host peripheral (e.g., SPI2_HOST, SPI3_HOST)
• cs_pin: GPIO pin for chip select
• reset_pin: GPIO pin for reset (use -1 if not connected)

Returns: SPI device handle on success, NULL on failure.

Display Control

ftb8md_show_string()

esp_err_t ftb8md_show_string(spi_device_handle_t handle, int digit, const char *str);

Display a string starting at the specified digit position.

Parameters:

• handle: SPI device handle
• digit: Starting digit position (0-7)
• str: Null-terminated string to display

ftb8md_clear_display()

esp_err_t ftb8md_clear_display(spi_device_handle_t handle);

Clear all digits and decimal points on the display.

ftb8md_set_dimming()

esp_err_t ftb8md_set_dimming(spi_device_handle_t handle, uint8_t level);

Set the display brightness level (0-240, where 240 is maximum brightness).

ftb8md_set_dot()

esp_err_t ftb8md_set_dot(spi_device_handle_t handle, int digit, bool dot_on);

Control the decimal point for a specific digit.

ftb8md_enter_standby()

esp_err_t ftb8md_enter_standby(spi_device_handle_t handle, bool standby);

Enter or exit standby (low power) mode.

ftb8md_set_display_power()

esp_err_t ftb8md_set_display_power(spi_device_handle_t handle, bool on);

Turn the display on or off. Display contents are preserved when off.

Custom Characters

ftb8md_write_custom_char()

esp_err_t ftb8md_write_custom_char(spi_device_handle_t handle, int char_index, const uint8_t grid_data[5]);

Define a custom 5x7 character pattern in CGRAM.

Parameters:

• handle: SPI device handle
• char_index: CGRAM index (0-7)
• grid_data: 5-byte array containing character pattern

ftb8md_set_addressed_char()

esp_err_t ftb8md_set_addressed_char(spi_device_handle_t handle, int digit, int char_index);

Display a custom character from CGRAM at specified digit.

Advanced Control

ftb8md_set_segment()

esp_err_t ftb8md_set_segment(spi_device_handle_t handle, int digit, uint8_t segments);

Directly control individual segments of a digit.

Display Memory Architecture

The Futaba 8-MD-06INK has several memory areas:

Memory	Description
DCRAM	Display Character RAM - stores character codes for each digit
CGROM	Character Generator ROM - built-in character patterns
CGRAM	Character Generator RAM - 8 user-defined characters
ADRAM	Additional Display RAM - controls decimal points

SPI Timing

• Clock Frequency: Max 500 kHz
• Mode: SPI Mode 3 (CPOL=1, CPHA=1)
• Bit Order: LSB First
• CS: Active Low

Examples

See the examples directory for complete usage examples:

• basic - Basic display operations
• custom_char - Custom character definition
• clock - Digital clock implementation

Troubleshooting

1. Display not responding:

   • Check SPI connections and pin assignments
   • Verify power supply voltage
   • Try using the reset pin

2. Garbled display:

   • Reduce SPI clock frequency
   • Check LSB-first bit order configuration

3. Dim display:

   • Increase dimming level with ftb8md_set_dimming()
   • Check power supply current capability

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please submit issues and pull requests on GitHub.