#define SSD1306_I2C_ADDRESS  0x3C

#define SSD1306_COMMAND   0x00
#define SSD1306_DATA   0xC0
#define SSD1306_DATA_CONTINUE 0x40

#define SSD1306_SET_CONTRAST_CONTROL     0x81
#define SSD1306_DISPLAY_ALL_ON_RESUME     0xA4
#define SSD1306_DISPLAY_ALL_ON       0xA5
#define SSD1306_NORMAL_DISPLAY       0xA6
#define SSD1306_INVERT_DISPLAY       0xA7
#define SSD1306_DISPLAY_OFF        0xAE
#define SSD1306_DISPLAY_ON        0xAF
#define SSD1306_NOP          0xE3

#define SSD1306_HORIZONTAL_SCROLL_RIGHT     0x26
#define SSD1306_HORIZONTAL_SCROLL_LEFT     0x27
#define SSD1306_HORIZONTAL_SCROLL_VERTICAL_AND_RIGHT 0x29
#define SSD1306_HORIZONTAL_SCROLL_VERTICAL_AND_LEFT  0x2A
#define SSD1306_DEACTIVATE_SCROLL      0x2E
#define SSD1306_ACTIVATE_SCROLL       0x2F
#define SSD1306_SET_VERTICAL_SCROLL_AREA    0xA3

#define SSD1306_SET_LOWER_COLUMN      0x00
#define SSD1306_SET_HIGHER_COLUMN      0x10
#define SSD1306_MEMORY_ADDR_MODE      0x20
#define SSD1306_SET_COLUMN_ADDR       0x21
#define SSD1306_SET_PAGE_ADDR       0x22

#define SSD1306_SET_START_LINE       0x40
#define SSD1306_SET_SEGMENT_REMAP      0xA0
#define SSD1306_SET_MULTIPLEX_RATIO      0xA8
#define SSD1306_COM_SCAN_DIR_INC      0xC0
#define SSD1306_COM_SCAN_DIR_DEC      0xC8
#define SSD1306_SET_DISPLAY_OFFSET      0xD3
#define SSD1306_SET_COM_PINS       0xDA
#define SSD1306_CHARGE_PUMP        0x8D

#define SSD1306_SET_DISPLAY_CLOCK_DIV_RATIO    0xD5
#define SSD1306_SET_PRECHARGE_PERIOD     0xD9
#define SSD1306_SET_VCOM_DESELECT      0xDB

#define SSD1306_WIDTH 128
#define SSD1306_HEIGHT 32

#define SSD1306_VRAM_SIZE (SSD1306_WIDTH * ((SSD1306_HEIGHT + 7) >> 3))

#define DMA_BUF_SZ (2 + (SSD1306_VRAM_SIZE))