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2.4 KiB

U8g2

Introduction

U8g2 is a monochrome graphics library for LCDs and OLEDs. It contains both drivers and high-level drawing routines.

The library is originally written for Arduino boards, but it runs just fine on other platforms, as long as the right drivers are available.

Usage

Just put USEPKG += u8g2 in your Makefile and #include "u8g2.h" to your code. Refer to the U8g2 wiki for more information on the API.

RIOT-OS interface

This package patches the original source to add an interface for RIOT-OS.

The following two callbacks add support for the included drivers via I2C and SPI peripherals:

  • u8x8_byte_riotos_hw_spi
  • u8x8_byte_riotos_hw_i2c

For timing and GPIO related operations, the following callback is available.

  • u8x8_gpio_and_delay_riotos

U8g2 needs to map pin numbers to RIOT-OS pin numbers. It also needs to know which peripheral to use. The following two methods can be used to set this information.

  • u8g2_SetPins(u8g2_dev, pins, bitmap)
  • u8g2_SetDevice(u8g2_dev, dev)

Note: pins should point to gpio_t array of U8g2 pin numbers to RIOT-OS pins. Due to this, pins can take up an additional 100 bytes, because it will use memory for the pins you do not map. You can overcome this limitation by implementing u8x8_gpio_and_delay_riotos yourself and hardcode the pins.

Example

u8g2_t u8g2;

gpio_t pins[] = {
    [U8X8_PIN_CS] = GPIO(PA, 0),
    [U8X8_PIN_DC] = GPIO(PA, 1),
    [U8X8_PIN_RESET] = GPIO(PA, 2)
};

uint32_t bitmap = (
    (1 << U8X8_PIN_CS) +
    (1 << U8X8_PIN_DC) +
    (1 << U8X8_PIN_RESET)
);

u8g2_Setup_ssd1306_128x64_noname_1(&u8g2, U8G2_R0, u8x8_byte_riotos_hw_spi, u8x8_gpio_and_delay_riotos);

u8g2_SetPins(&u8g2, pins, bitmap);
u8g2_SetDevice(&u8g2, SPI_DEV(0));

Virtual displays

For targets without an I2C or SPI, virtual displays are available. These displays are part of U8g2, but are not compiled by default.

  • By adding USEMODULE += u8g2_utf8, a terminal display is used as virtual display, using UTF8 block characters that are printed to stdout.
  • By adding USEMODULE += u8g2_sdl, a SDL virtual display will be used. This is only available on native targets that have SDL installed. It uses sdl-config to find the headers and libraries. Note that RIOT-OS builds 32-bit binaries and requires 32-bit SDL libraries.

Example

u8g2_t u8g2;

u8g2_SetupBuffer_Utf8(&u8g2, U8G2_R0);