u8g2-oled-draw

:::warning [UNTESTED] native_sim build-and-run only; not yet run on a bench SoM. :::

Render text, a frame, and a box into a RAM framebuffer with u8g2, then dump the buffer to the console as ASCII art.

Source: examples/display/u8g2-oled-draw/.

What it does

Sets up a u8g2_t against a hand-written null device (src/u8g2_ram_null.c, 64×32, never touches a bus) via u8g2_SetupDisplay() / u8g2_SetupBuffer(), then calls u8g2_DrawFrame(), u8g2_DrawBox(), and u8g2_SetFont() + u8g2_DrawStr(). Finally it dumps the RAM tile buffer as ASCII.

The teaching point: u8g2 draws through an abstract device callback (u8x8_msg_cb). The same u8g2_t and the same draw calls run whether that callback pushes tiles over I²C/SPI to a real SSD1306, or — as here — does nothing at all and leaves the drawing in RAM.

u8g2 ships no zephyr/module.yml upstream, so libraries: [u8g2] sets CONFIG_ALP_SDK_U8G2_VENDORED_CORE, which gates the SDK's Zephyr module compiling the vendored core draw pipeline.

Hardware swap: a real SSD1306

Swap u8g2_ram_null_Setup() for a generated panel setup, e.g. u8g2_Setup_ssd1306_64x32_1f(). The u8g2_t and every draw call afterwards are unchanged. u8g2_InitDisplay() — commented out in main.c — becomes required on real hardware.

# board.yaml
cores:
  m55_hp:
    peripherals:
      - i2c        # or spi, depending on the panel's wiring
chips:
  - ssd1306

board.yaml

As shipped there is no panel peripheral: no i2c / spi, no chips: entry.

libraries:
  - name: u8g2
    cores: [m55_hp]

som:
  sku: E1M-AEN801

preset: e1m-evk
cores:
  m55_hp:
    app: ./src
    peripherals: []

diagnostics:
  log_level: info

Expected output

The real dump is 32 lines of 64 characters; this is trimmed. The string alp renders as pixels near the bottom of the frame, not as literal text.

[u8g2-oled-draw] 64x32 canvas (# = lit pixel):
................................................................
.##############################################################.
.#............................................................#.
.#..##########..................................................#.
...
.#............................alp..............................#.
.##############################################################.
................................................................
[u8g2-oled-draw] done

See also

• gfx-compat-blit — the RGB565 fill/blit shim
• Examples overview