Arduino Uno + Adafruit SSD1306 - etch a sketch

gistfile1.ino

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// If using software SPI (the default case):
#define OLED_MOSI   9 // data
#define OLED_CLK   10
#define OLED_DC    11
#define OLED_CS    12
#define OLED_RESET 13
Adafruit_SSD1306 lcd(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

#define BUTTON_LEFT  4
#define BUTTON_RIGHT 5

#define SERIAL_UPDATE_INTERVAL_MILLIS 1000

void setup(void)
{
  Serial.begin(9600);
  
  // by default, we'll generate the high voltage from the 3.3v line internally! (neat!)
  lcd.begin(SSD1306_SWITCHCAPVCC);
  // init done
  lcd.display();
  delay(2000);
  lcd.clearDisplay();
  
  
  testdrawcircle();
  lcd.display();
  delay(2000);
  lcd.clearDisplay();
  
  
  drawClear();

  pinMode(BUTTON_LEFT, INPUT);
  digitalWrite(BUTTON_LEFT, HIGH);
  pinMode(BUTTON_RIGHT, INPUT);
  digitalWrite(BUTTON_RIGHT, HIGH);
}

void drawCursor(int h, int v)
{
  // TODO(pim): Overlay a crosshair on the cursor so we know where we are if
  //            the pen is up.
}

void drawClear(void)
{
  for (int y = 0; y < SSD1306_LCDHEIGHT; y++) {
    if (y>0) {
      for(int x = 0; x < SSD1306_LCDWIDTH; x++) {
        lcd.drawPixel(x, y-1, 0);
      }
    }
    lcd.drawFastVLine(0,y,SSD1306_LCDWIDTH-1,y);
    lcd.display();
    delay(8);
  }
  lcd.clearDisplay();
}



void testdrawcircle(void) {
  for (int16_t i=0; i<lcd.height(); i+=2) {
    lcd.drawCircle(lcd.width()/2, lcd.height()/2, i, WHITE);
    lcd.display();
  }
}


void loop(void)
{
  static bool penDown = false;
  static int phase = 0;
  static unsigned long next_serial_timestamp = 0;
  int H = map(analogRead(A0), 0, 1023, 0, SSD1306_LCDWIDTH - 1);
  int V = map(analogRead(A1), 0, 1023, 0, SSD1306_LCDHEIGHT - 1);


  if (digitalRead(BUTTON_LEFT) == LOW) {
    Serial.println("BUTTON_LEFT pushed");
    penDown = false;
    drawClear();
    while (digitalRead(BUTTON_LEFT) == LOW) ;
  }

  if (digitalRead(BUTTON_RIGHT) == LOW) {
    Serial.println("BUTTON_RIGHT pushed");
    penDown = !penDown;
    while (digitalRead(BUTTON_RIGHT) == LOW) ;
  }

  if (next_serial_timestamp < millis()) {
    Serial.print("Pen is ");
    Serial.println(penDown ? "down" : "up");
    Serial.print("H="); 
    Serial.println(H);
    Serial.print("V="); 
    Serial.println(V);
    next_serial_timestamp = millis() + SERIAL_UPDATE_INTERVAL_MILLIS;
  }

  drawCursor(H, V);
  if (penDown) {
    lcd.drawPixel(H, V, WHITE);
  }
  lcd.display();
}