U8x8 Fonts Guide

u8x8 fonts

u8x8 is a compact font and display helper used primarily with small monochrome OLED, LCD, and LED displays in embedded systems (especially Arduino and ESP-based projects). It’s part of the u8g2/u8x8 ecosystem but focuses on a minimal, byte-oriented interface and very small memory footprint.

C. Modern & Square

  • u8x8_font_chroma48mid8_r: A distinct, slightly rounded look.
  • u8x8_font_px437wyse700b: A Wyse terminal font (very clean).
  • u8x8_font_saikyosans): A thick, bold pixel font.

Memory Layout

Because microcontrollers are resource-constrained, u8x8 fonts store data vertically or horizontally depending on the display controller. For example, an OLED display (SSD1306) uses a vertical page layout. The 8 bytes for the letter 'A' might represent Column 0, Pages 0-7.

The beauty of u8x8 fonts is that this rendering math is simple. To draw an 'A' at column 5, row 2, the library simply copies 8 bytes of pre-defined font data to the display's memory at a specific offset. No bit-shifting, no clipping, no complex math.

Key points

  • Purpose: Provide tiny bitmap fonts and a simple API for drawing text on low-resource displays.
  • Format: Fonts are stored as arrays of bytes where each byte (or group of bytes) encodes glyph bitmaps row-by-row or column-by-column depending on display orientation. Glyph metadata (width, height, encoding) is minimal to save space.
  • Memory profile: Designed for microcontrollers with limited RAM/flash — glyphs are typically stored in program flash and accessed directly with low RAM overhead.
  • Supported glyph sizes: Common sizes include 6x8 and 8x8 pixels per glyph, plus a few proportional or taller variants; the naming convention often indicates glyph width × height (e.g., 8x8).
  • Rendering: u8x8 uses byte-oriented writes and simple character mapping; it does not require complex graphics buffering. This enables direct writes to displays via I2C/SPI with small code.
  • Use cases: Status messages, menus, numeric displays, small icons, or any UI where compact text is required and memory/CPU are constrained.
  • Integration: Often used with the u8g2 library suite; u8x8 provides the minimal text-only backend while u8g2 offers richer graphics and larger font sets.
  • Advantages:
    • Extremely low RAM usage
    • Fast, simple rendering
    • Easy to port to new displays/drivers
  • Limitations:
    • Restricted to monochrome and small glyphs
    • Limited international/Unicode support unless glyphs are added
    • Lacks advanced typographic features (antialiasing, kerning)

Characteristics

  • Resolution: 8x8 pixels per character
  • Bitmapped: Each character is represented by a fixed bitmap
  • Monospaced: All characters have the same width
  • Limited scalability: Difficult to scale up or down without losing quality

Creating Your Own u8x8 Font

The standard fonts are great, but what if you need Japanese characters, custom icons, or a specific corporate logo? You can create custom u8x8 fonts. u8x8 fonts

The U8g2 library includes a tool called bdfconv (BDF Converter). BDF (Glyph Bitmap Distribution Format) is a standard text-based font format.

Workflow:

  1. Design your 8x8 glyphs in a font editor like FontForge or a simple online tool like Piskel.
  2. Export the glyphs as a BDF file.
  3. Use bdfconv to convert the BDF into a C array compatible with U8x8.
  4. Include the generated .c file in your project.

Alternatively, you can manually define a font in C: u8x8 fonts u8x8 is a compact font and

static const uint8_t my_custom_font[] = 
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Space
  0x00, 0x00, 0x5F, 0x00, 0x00, 0x00, 0x00, 0x00, // !
  // ... and so on for 256 characters
;

(Note: The order of bytes depends on your display's page layout.)

The Bitmap Tile

A u8x8 font is essentially a lookup table of bitmaps. Each character (ASCII 0-255) corresponds to a specific pattern of bits.

  • The "8" in u8x8: This implies the font tile is 8 pixels wide.
  • The "x" in u8x8: This implies the font tile is 8 pixels high.

So, a standard u8x8 font map stores 256 characters, where each character is an 8x8 pixel bitmap (64 bits, or 8 bytes of data). u8x8_font_chroma48mid8_r : A distinct, slightly rounded look

D. Scaled Fonts

U8x8 allows you to use scaled fonts to make text larger without loading a different font file.

  • u8x8_font_px437wyse700a_2x2_r: A 2x scaled version. One character takes 16x16 pixels.
  • u8x8_font_lucasarts_scumm_subtitle_r_2x2: Used for big subtitles.

U8x8 vs U8g2 Fonts – When to Use Which?

| Feature | U8x8 Fonts | U8g2 Fonts | |------------------------|--------------------------|---------------------------| | Width | Fixed (monospaced) | Proportional (variable) | | Pixel size | Usually 8x8 or 8x16 | Any size (e.g., 6x10, 12x16) | | RAM buffer | None (direct render) | Required (full frame buffer) | | Speed | Very fast | Slower (more data) | | Graphics drawing | No (text only) | Yes (lines, circles, bitmaps) | | Display orientation | Fixed grid | Pixel-perfect positioning | | Typical use | Menus, logs, terminals | Graphics, mixed text/shapes |

Rule of thumb: Use U8x8 for text-heavy, low-memory projects. Use U8g2 when you need graphics or precise positioning.