""" Program 12-2: OLED_SSD1306 via I2C
    This program communicates with the OLED_SSD1306 via I2C.
    It uses framebuf.
    Connection: SCL - GP17, SDA - GP16
 """

import time
import framebuf
from machine import I2C, Pin

DEV_ADDR = 0x3C
SCREEN_WIDTH = 128
SCREEN_HEIGHT = 64
SCREEN_PAGE_NUM = 8
SSD1306_WHITE = 1
SSD1306_BLACK = 0

# Instantiate i2c with SCL - GP17, SDA - GP16
i2c = I2C(0, scl = Pin(17), sda = Pin(16), freq = 400_000)

# Instantiate a frame buffer
buffer = bytearray(SCREEN_WIDTH * SCREEN_HEIGHT // 8)
fbuf = framebuf.FrameBuffer(buffer, SCREEN_WIDTH, SCREEN_HEIGHT, framebuf.MONO_VLSB)


def ssd1306_data(data):
    """Write a byte of data to SSD1306"""
    i2c.writeto(DEV_ADDR, bytearray([0xC0, data]))


def ssd1306_command(cmd):
    """Write a byte of command to SSD1306"""
    i2c.writeto(DEV_ADDR, bytearray([0x80, cmd]))


def ssd1306_init():
    """Initialize SSD1306"""
    INIT_SEQ = (
        0xae,       # turn off oled panel
        0x00,       # set low column address
        0x10,       # set high column address
        0x40,       # set start line address
        0x20, 0x02, # page addressing mode
        0xc8,       # top-down segment (4th quadrant)
        0x81,       # set contrast control register
        0xcf, 0xa1, # set segment re-map 95 to 0
        0xa6,       # set normal display
        0xa8,       # set multiplex ratio(1 to 64)
        0x3f,       # 1/64 duty
        0xd3,       # set display offset
        0x00,       # not offset
        0xd5,       # set display clock divide ratio/oscillator frequency
        0x80,       # set divide ratio
        0xd9,       # set pre-charge period
        0xf1, 0xda, # set com pins hardware configuration
        0x12, 0xdb, # set vcomh
        0x40, 0x8d, # set Charge Pump enable/disable
        0x14,       # set(0x10) disable
        0xaf        # turn on oled panel
        )

    time.sleep_ms(100)

    for command in INIT_SEQ:
        ssd1306_command(command)


def ssd1306_setRegion(x0, x1, y):
    """Set active region to x0, x1, y, y.
       The maximum region can be set is a page."""
    ssd1306_command(0x21)       # set column
    ssd1306_command(x0)         # starting column
    ssd1306_command(x1)         # end column
    ssd1306_command(0x22)       # set page
    ssd1306_command(y)          # starting page
    ssd1306_command(y)          # end page


def ssd1306_flush():
    """Write the buffer to the display one page at a time"""
    for page in range(SCREEN_PAGE_NUM):
        ssd1306_setRegion(0, SCREEN_WIDTH - 1, page)
        for column in range(SCREEN_WIDTH):
            ssd1306_data(buffer[page * SCREEN_WIDTH + column])


# Initialize the SSD1306 controller
ssd1306_init()            

# Write a message
fbuf.fill(SSD1306_BLACK)
fbuf.text('Hello from', 0, 5, SSD1306_WHITE)
fbuf.text('MicroPython.', 20, 16, SSD1306_WHITE)

# Draw nested rectangles
x = 10
y = 30
w = SCREEN_WIDTH - 20
h = SCREEN_HEIGHT - 30
c = SSD1306_WHITE

while h > 0:
    fbuf.fill_rect(x, y, w, h, c)
    x += 2
    y += 2
    w -= 4
    h -= 4
    c = SSD1306_WHITE if c == SSD1306_BLACK else SSD1306_BLACK

# Write the frame buffer out to the display
ssd1306_flush()