/* Smooth Big Text - see http://www.technoblogy.com/show?3AJ7

   David Johnson-Davies - www.technoblogy.com - 21st October 2020
   ATtiny85 @ 1 MHz (internal oscillator; BOD disabled)
   
   CC BY 4.0
   Licensed under a Creative Commons Attribution 4.0 International license: 
   http://creativecommons.org/licenses/by/4.0/
*/

#include <Wire.h>
#include <avr/sleep.h>

// OLED I2C 128 x 32 monochrome display **********************************************

const int OLEDAddress = 0x3C;

// Initialisation sequence for OLED module
int const InitLen = 15;
const unsigned char Init[InitLen] PROGMEM = {
  0xA8, // Set multiplex
  0x1F, // for 32 rows
  0x8D, // Charge pump
  0x14, 
  0x20, // Memory mode
  0x01, // Vertical addressing
  0xA1, // 0xA0/0xA1 flip horizontally
  0xC8, // 0xC0/0xC8 flip vertically
  0xDA, // Set comp ins
  0x02,
  0xD9, // Set pre charge
  0xF1,
  0xDB, // Set vcom deselect
  0x40,
  0xAF  // Display on
};

const int data = 0x40;
const int single = 0x80;
const int command = 0x00;

void InitDisplay () {
  Wire.beginTransmission(OLEDAddress);
  Wire.write(command);
  for (uint8_t c=0; c<InitLen; c++) Wire.write(pgm_read_byte(&Init[c]));
  Wire.endTransmission();
}

void DisplayOnOff (int On) {
  Wire.beginTransmission(OLEDAddress);
  Wire.write(command);
  Wire.write(0xAE + On);
  Wire.endTransmission();
}

// Graphics **********************************************

int Scale = 1;
boolean Smooth = false;
const int Space = 11;
const int Dash = 12;
const int Hz = 13;
const int Icon = 15;

// Character set for text - stored in program memory
const uint8_t CharMap[96][6] PROGMEM = {
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }, 
{ 0x00, 0x00, 0x5F, 0x00, 0x00, 0x00 }, 
{ 0x00, 0x07, 0x00, 0x07, 0x00, 0x00 }, 
{ 0x14, 0x7F, 0x14, 0x7F, 0x14, 0x00 }, 
{ 0x24, 0x2A, 0x7F, 0x2A, 0x12, 0x00 }, 
{ 0x23, 0x13, 0x08, 0x64, 0x62, 0x00 }, 
{ 0x36, 0x49, 0x56, 0x20, 0x50, 0x00 }, 
{ 0x00, 0x08, 0x07, 0x03, 0x00, 0x00 }, 
{ 0x00, 0x1C, 0x22, 0x41, 0x00, 0x00 }, 
{ 0x00, 0x41, 0x22, 0x1C, 0x00, 0x00 }, 
{ 0x2A, 0x1C, 0x7F, 0x1C, 0x2A, 0x00 }, 
{ 0x08, 0x08, 0x3E, 0x08, 0x08, 0x00 }, 
{ 0x00, 0x80, 0x70, 0x30, 0x00, 0x00 }, 
{ 0x08, 0x08, 0x08, 0x08, 0x08, 0x00 }, 
{ 0x00, 0x00, 0x60, 0x60, 0x00, 0x00 }, 
{ 0x20, 0x10, 0x08, 0x04, 0x02, 0x00 }, 
{ 0x3E, 0x51, 0x49, 0x45, 0x3E, 0x00 }, 
{ 0x00, 0x42, 0x7F, 0x40, 0x00, 0x00 }, 
{ 0x72, 0x49, 0x49, 0x49, 0x46, 0x00 }, 
{ 0x21, 0x41, 0x49, 0x4D, 0x33, 0x00 }, 
{ 0x18, 0x14, 0x12, 0x7F, 0x10, 0x00 }, 
{ 0x27, 0x45, 0x45, 0x45, 0x39, 0x00 }, 
{ 0x3C, 0x4A, 0x49, 0x49, 0x31, 0x00 }, 
{ 0x41, 0x21, 0x11, 0x09, 0x07, 0x00 }, 
{ 0x36, 0x49, 0x49, 0x49, 0x36, 0x00 }, 
{ 0x46, 0x49, 0x49, 0x29, 0x1E, 0x00 }, 
{ 0x00, 0x00, 0x14, 0x00, 0x00, 0x00 }, 
{ 0x00, 0x40, 0x34, 0x00, 0x00, 0x00 }, 
{ 0x00, 0x08, 0x14, 0x22, 0x41, 0x00 }, 
{ 0x14, 0x14, 0x14, 0x14, 0x14, 0x00 }, 
{ 0x00, 0x41, 0x22, 0x14, 0x08, 0x00 }, 
{ 0x02, 0x01, 0x59, 0x09, 0x06, 0x00 }, 
{ 0x3E, 0x41, 0x5D, 0x59, 0x4E, 0x00 }, 
{ 0x7C, 0x12, 0x11, 0x12, 0x7C, 0x00 }, 
{ 0x7F, 0x49, 0x49, 0x49, 0x36, 0x00 }, 
{ 0x3E, 0x41, 0x41, 0x41, 0x22, 0x00 }, 
{ 0x7F, 0x41, 0x41, 0x41, 0x3E, 0x00 }, 
{ 0x7F, 0x49, 0x49, 0x49, 0x41, 0x00 }, 
{ 0x7F, 0x09, 0x09, 0x09, 0x01, 0x00 }, 
{ 0x3E, 0x41, 0x41, 0x51, 0x73, 0x00 }, 
{ 0x7F, 0x08, 0x08, 0x08, 0x7F, 0x00 }, 
{ 0x00, 0x41, 0x7F, 0x41, 0x00, 0x00 }, 
{ 0x20, 0x40, 0x41, 0x3F, 0x01, 0x00 }, 
{ 0x7F, 0x08, 0x14, 0x22, 0x41, 0x00 }, 
{ 0x7F, 0x40, 0x40, 0x40, 0x40, 0x00 }, 
{ 0x7F, 0x02, 0x1C, 0x02, 0x7F, 0x00 }, 
{ 0x7F, 0x04, 0x08, 0x10, 0x7F, 0x00 }, 
{ 0x3E, 0x41, 0x41, 0x41, 0x3E, 0x00 }, 
{ 0x7F, 0x09, 0x09, 0x09, 0x06, 0x00 }, 
{ 0x3E, 0x41, 0x51, 0x21, 0x5E, 0x00 }, 
{ 0x7F, 0x09, 0x19, 0x29, 0x46, 0x00 }, 
{ 0x26, 0x49, 0x49, 0x49, 0x32, 0x00 }, 
{ 0x03, 0x01, 0x7F, 0x01, 0x03, 0x00 }, 
{ 0x3F, 0x40, 0x40, 0x40, 0x3F, 0x00 }, 
{ 0x1F, 0x20, 0x40, 0x20, 0x1F, 0x00 }, 
{ 0x3F, 0x40, 0x38, 0x40, 0x3F, 0x00 }, 
{ 0x63, 0x14, 0x08, 0x14, 0x63, 0x00 }, 
{ 0x03, 0x04, 0x78, 0x04, 0x03, 0x00 }, 
{ 0x61, 0x59, 0x49, 0x4D, 0x43, 0x00 }, 
{ 0x00, 0x7F, 0x41, 0x41, 0x41, 0x00 }, 
{ 0x02, 0x04, 0x08, 0x10, 0x20, 0x00 }, 
{ 0x00, 0x41, 0x41, 0x41, 0x7F, 0x00 }, 
{ 0x04, 0x02, 0x01, 0x02, 0x04, 0x00 }, 
{ 0x40, 0x40, 0x40, 0x40, 0x40, 0x00 }, 
{ 0x00, 0x03, 0x07, 0x08, 0x00, 0x00 }, 
{ 0x20, 0x54, 0x54, 0x78, 0x40, 0x00 }, 
{ 0x7F, 0x28, 0x44, 0x44, 0x38, 0x00 }, 
{ 0x38, 0x44, 0x44, 0x44, 0x28, 0x00 }, 
{ 0x38, 0x44, 0x44, 0x28, 0x7F, 0x00 }, 
{ 0x38, 0x54, 0x54, 0x54, 0x18, 0x00 }, 
{ 0x00, 0x08, 0x7E, 0x09, 0x02, 0x00 }, 
{ 0x18, 0xA4, 0xA4, 0x9C, 0x78, 0x00 }, 
{ 0x7F, 0x08, 0x04, 0x04, 0x78, 0x00 }, 
{ 0x00, 0x44, 0x7D, 0x40, 0x00, 0x00 }, 
{ 0x20, 0x40, 0x40, 0x3D, 0x00, 0x00 }, 
{ 0x7F, 0x10, 0x28, 0x44, 0x00, 0x00 }, 
{ 0x00, 0x41, 0x7F, 0x40, 0x00, 0x00 }, 
{ 0x7C, 0x04, 0x78, 0x04, 0x78, 0x00 }, 
{ 0x7C, 0x08, 0x04, 0x04, 0x78, 0x00 }, 
{ 0x38, 0x44, 0x44, 0x44, 0x38, 0x00 }, 
{ 0xFC, 0x18, 0x24, 0x24, 0x18, 0x00 }, 
{ 0x18, 0x24, 0x24, 0x18, 0xFC, 0x00 }, 
{ 0x7C, 0x08, 0x04, 0x04, 0x08, 0x00 }, 
{ 0x48, 0x54, 0x54, 0x54, 0x24, 0x00 }, 
{ 0x04, 0x04, 0x3F, 0x44, 0x24, 0x00 }, 
{ 0x3C, 0x40, 0x40, 0x20, 0x7C, 0x00 }, 
{ 0x1C, 0x20, 0x40, 0x20, 0x1C, 0x00 }, 
{ 0x3C, 0x40, 0x30, 0x40, 0x3C, 0x00 }, 
{ 0x44, 0x28, 0x10, 0x28, 0x44, 0x00 }, 
{ 0x4C, 0x90, 0x90, 0x90, 0x7C, 0x00 }, 
{ 0x44, 0x64, 0x54, 0x4C, 0x44, 0x00 }, 
{ 0x00, 0x08, 0x36, 0x41, 0x00, 0x00 }, 
{ 0x00, 0x00, 0x77, 0x00, 0x00, 0x00 }, 
{ 0x00, 0x41, 0x36, 0x08, 0x00, 0x00 }, 
{ 0x02, 0x01, 0x02, 0x04, 0x02, 0x00 }, 
{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }
};

void ClearDisplay () {
  Wire.beginTransmission(OLEDAddress);
  Wire.write(command);
  // Set column address range
  Wire.write(0x21); Wire.write(0); Wire.write(127);
  // Set page address range
  Wire.write(0x22); Wire.write(0); Wire.write(3);
  Wire.endTransmission();
  // Write the data in 26 20-byte transmissions
  for (int i = 0 ; i < 26; i++) {
    Wire.beginTransmission(OLEDAddress);
    Wire.write(data);
    for (int i = 0 ; i < 20; i++) Wire.write(0);
    Wire.endTransmission();
  }
}

// Converts bit pattern abcdefgh into aabbccddeeffgghh
int Stretch (int x) {
  x = (x & 0xF0)<<4 | (x & 0x0F);
  x = (x<<2 | x) & 0x3333;
  x = (x<<1 | x) & 0x5555;
  return x | x<<1;
}

// Plots a character; line = 0 to 3; column = 0 to 131
void PlotChar(int c, int line, int column) {
  Wire.beginTransmission(OLEDAddress);
  Wire.write(command);
  // Set column address range
  Wire.write(0x21); Wire.write(column); Wire.write(column + Scale*6 - 1);
  // Set page address range
  Wire.write(0x22); Wire.write(line); Wire.write(line + Scale - 1);
  Wire.endTransmission();
  Wire.beginTransmission(OLEDAddress);
  Wire.write(data);
  uint8_t col0 = pgm_read_byte(&CharMap[c-32][0]);
  int col0L, col0R, col1L, col1R;
  col0L = Stretch(col0);
  col0R = col0L;
  for (uint8_t col = 1 ; col < 5; col++) {
    uint8_t col1 = pgm_read_byte(&CharMap[c-32][col]);
    col1L = Stretch(col1);
    col1R = col1L;
    if (Scale == 1) Wire.write(col0);
    // Smoothing
    else {
      if (Smooth) {
        for (int i=6; i>=0; i--) {
          for (int j=1; j<3; j++) {
            if (((col0>>i & 0b11) == (3-j)) && ((col1>>i & 0b11) == j)) {
              col0R = col0R | 1<<((i*2)+j);
              col1L = col1L | 1<<((i*2)+3-j);
            }
          }
        }
      }
      Wire.write(col0L); Wire.write(col0L>>8); 
      Wire.write(col0R); Wire.write(col0R>>8);
      col0L = col1L; col0R = col1R;
    }
    col0 = col1;
  }
  if (Scale == 1) Wire.write(col0);
  else {
    Wire.write(col0L); Wire.write(col0L>>8); 
    Wire.write(col0R); Wire.write(col0R>>8); 
  } 
  Wire.endTransmission();
}

// Plot text starting at the current plot position
void PlotText(PGM_P s, int line, int column) {
  int p = (int)s;
  while (1) {
    char c = pgm_read_byte(p++);
    if (c == 0) return;
    PlotChar(c, line, column);
    column = column + Scale*6;
  }
}

// Setup **********************************************

void setup() {
  Wire.begin();
  InitDisplay();
  ClearDisplay();
  Scale = 2;
}

void loop() {
  Smooth = true;
  PlotText(PSTR("ABCDEFGHIJ"), 0, 0);
  PlotText(PSTR("0123456789"), 2, 0);
  delay(10000);
  Smooth = false;
  PlotText(PSTR("ABCDEFGHIJ"), 0, 0);
  PlotText(PSTR("0123456789"), 2, 0);
  delay(10000);
}