qmk-firmware/platforms/avr/drivers/ssd1306.h

#pragma once

#include <stdbool.h>
#include <stdio.h>
#include "config.h"

enum ssd1306_cmds {
    DisplayOff = 0xAE,
    DisplayOn  = 0xAF,

    SetContrast        = 0x81,
    DisplayAllOnResume = 0xA4,

    DisplayAllOn       = 0xA5,
    NormalDisplay      = 0xA6,
    InvertDisplay      = 0xA7,
    SetDisplayOffset   = 0xD3,
    SetComPins         = 0xda,
    SetVComDetect      = 0xdb,
    SetDisplayClockDiv = 0xD5,
    SetPreCharge       = 0xd9,
    SetMultiPlex       = 0xa8,
    SetLowColumn       = 0x00,
    SetHighColumn      = 0x10,
    SetStartLine       = 0x40,

    SetMemoryMode = 0x20,
    ColumnAddr    = 0x21,
    PageAddr      = 0x22,

    ComScanInc    = 0xc0,
    ComScanDec    = 0xc8,
    SegRemap      = 0xa0,
    SetChargePump = 0x8d,
    ExternalVcc   = 0x01,
    SwitchCapVcc  = 0x02,

    ActivateScroll                   = 0x2f,
    DeActivateScroll                 = 0x2e,
    SetVerticalScrollArea            = 0xa3,
    RightHorizontalScroll            = 0x26,
    LeftHorizontalScroll             = 0x27,
    VerticalAndRightHorizontalScroll = 0x29,
    VerticalAndLeftHorizontalScroll  = 0x2a,
};

// Controls the SSD1306 128x32 OLED display via i2c

#ifndef SSD1306_ADDRESS
#    define SSD1306_ADDRESS 0x3C
#endif

#define DisplayHeight 32
#define DisplayWidth 128

#define FontHeight 8
#define FontWidth 6

#define MatrixRows (DisplayHeight / FontHeight)
#define MatrixCols (DisplayWidth / FontWidth)

struct CharacterMatrix {
    uint8_t  display[MatrixRows][MatrixCols];
    uint8_t *cursor;
    bool     dirty;
};

extern struct CharacterMatrix display;

bool iota_gfx_init(void);
void iota_gfx_task(void);
bool iota_gfx_off(void);
bool iota_gfx_on(void);
void iota_gfx_flush(void);
void iota_gfx_write_char(uint8_t c);
void iota_gfx_write(const char *data);
void iota_gfx_write_P(const char *data);
void iota_gfx_clear_screen(void);

void iota_gfx_task_user(void);

void matrix_clear(struct CharacterMatrix *matrix);
void matrix_write_char_inner(struct CharacterMatrix *matrix, uint8_t c);
void matrix_write_char(struct CharacterMatrix *matrix, uint8_t c);
void matrix_write(struct CharacterMatrix *matrix, const char *data);
void matrix_write_P(struct CharacterMatrix *matrix, const char *data);
void matrix_render(struct CharacterMatrix *matrix);