Joystick OLED Sketchpad

#include <Arduino.h>
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_ILI9341.h>


// Forward declarations
void drawStatus();
void drawCursor(int x, int y);
void eraseCursor(int x, int y);
void clearCanvas();
void moveCursorFromJoystick();
void readControls();

constexpr uint8_t TFT_MOSI_PIN = 10;
constexpr uint8_t TFT_MISO_PIN = 9;
constexpr uint8_t TFT_SCK_PIN = 6;
constexpr uint8_t TFT_CS_PIN = 7;
constexpr uint8_t TFT_DC_PIN = 0;
constexpr uint8_t TFT_RST_PIN = 1;
constexpr uint8_t TOUCH_CS_PIN = 8;
constexpr uint8_t JOYSTICK_X_PIN = 2;
constexpr uint8_t JOYSTICK_Y_PIN = 3;
constexpr uint8_t JOYSTICK_SWITCH_PIN = 4;
constexpr uint8_t CLEAR_BUTTON_PIN = 5;

constexpr int SCREEN_WIDTH = 320;
constexpr int SCREEN_HEIGHT = 240;
constexpr int STATUS_HEIGHT = 24;
constexpr int CANVAS_TOP = STATUS_HEIGHT;
constexpr int CURSOR_STEP = 3;
constexpr int CENTER_LOW = 1300;
constexpr int CENTER_HIGH = 2800;
constexpr unsigned long MOVE_INTERVAL_MS = 55;
constexpr unsigned long DEBOUNCE_MS = 35;
constexpr unsigned long HOLD_MS = 750;
constexpr uint8_t COLOR_COUNT = 8;

Adafruit_ILI9341 display(TFT_CS_PIN, TFT_DC_PIN, TFT_RST_PIN);

const uint16_t brushColors[COLOR_COUNT] = {
  ILI9341_WHITE, ILI9341_RED, ILI9341_GREEN, ILI9341_BLUE,
  ILI9341_YELLOW, ILI9341_CYAN, ILI9341_MAGENTA, ILI9341_ORANGE
};
const char *colorNames[COLOR_COUNT] = {
  "WHITE", "RED", "GREEN", "BLUE", "YELLOW", "CYAN", "MAGENTA", "ORANGE"
};

int cursorX = SCREEN_WIDTH / 2;
int cursorY = (CANVAS_TOP + SCREEN_HEIGHT) / 2;
uint8_t colorIndex = 0;
bool eraseMode = false;
bool joystickWasDown = false;
bool joystickHoldHandled = false;
bool clearWasDown = false;
unsigned long joystickDownMs = 0;
unsigned long lastMoveMs = 0;
unsigned long lastClearPressMs = 0;

void drawStatus() {
  display.fillRect(0, 0, SCREEN_WIDTH, STATUS_HEIGHT, ILI9341_DARKGREY);
  display.setTextSize(2);
  display.setTextColor(ILI9341_WHITE, ILI9341_DARKGREY);
  display.setCursor(5, 4);
  if (eraseMode) {
    display.print("ERASE");
  } else {
    display.print("DRAW ");
    display.setTextColor(brushColors[colorIndex], ILI9341_DARKGREY);
    display.print(colorNames[colorIndex]);
  }
  display.setTextColor(ILI9341_WHITE, ILI9341_DARKGREY);
  display.setCursor(174, 4);
  display.print("hold=mode");
}

void drawCursor(int x, int y) {
  uint16_t cursorColor = eraseMode ? ILI9341_WHITE : brushColors[colorIndex];
  display.drawRect(x - 3, y - 3, 7, 7, cursorColor);
}

void eraseCursor(int x, int y) {
  display.drawRect(x - 3, y - 3, 7, 7, ILI9341_BLACK);
}

void clearCanvas() {
  display.fillRect(0, CANVAS_TOP, SCREEN_WIDTH, SCREEN_HEIGHT - CANVAS_TOP, ILI9341_BLACK);
  drawStatus();
}

void moveCursorFromJoystick() {
  if (millis() - lastMoveMs < MOVE_INTERVAL_MS) return;

  int xReading = analogRead(JOYSTICK_X_PIN);
  int yReading = analogRead(JOYSTICK_Y_PIN);
  int dx = 0;
  int dy = 0;
  if (xReading < CENTER_LOW) dx = -CURSOR_STEP;
  else if (xReading > CENTER_HIGH) dx = CURSOR_STEP;
  if (yReading < CENTER_LOW) dy = -CURSOR_STEP;
  else if (yReading > CENTER_HIGH) dy = CURSOR_STEP;
  if (dx == 0 && dy == 0) return;

  eraseCursor(cursorX, cursorY);
  int oldX = cursorX;
  int oldY = cursorY;
  cursorX = constrain(cursorX + dx, 3, SCREEN_WIDTH - 4);
  cursorY = constrain(cursorY + dy, CANVAS_TOP + 3, SCREEN_HEIGHT - 4);
  uint16_t paintColor = eraseMode ? ILI9341_BLACK : brushColors[colorIndex];
  display.drawLine(oldX, oldY, cursorX, cursorY, paintColor);
  drawCursor(cursorX, cursorY);
  lastMoveMs = millis();
}

void readControls() {
  const unsigned long now = millis();
  const bool joystickDown = digitalRead(JOYSTICK_SWITCH_PIN) == LOW;
  const bool clearDown = digitalRead(CLEAR_BUTTON_PIN) == LOW;

  if (joystickDown && !joystickWasDown) {
    joystickDownMs = now;
    joystickHoldHandled = false;
  }
  if (joystickDown && !joystickHoldHandled && now - joystickDownMs >= HOLD_MS) {
    eraseCursor(cursorX, cursorY);
    eraseMode = !eraseMode;
    drawStatus();
    drawCursor(cursorX, cursorY);
    joystickHoldHandled = true;
  }
  if (!joystickDown && joystickWasDown && !joystickHoldHandled && now - joystickDownMs > DEBOUNCE_MS) {
    eraseCursor(cursorX, cursorY);
    colorIndex = (colorIndex + 1) % COLOR_COUNT;
    eraseMode = false;
    drawStatus();
    drawCursor(cursorX, cursorY);
  }

  if (clearDown && !clearWasDown && now - lastClearPressMs > DEBOUNCE_MS) {
    clearCanvas();
    drawCursor(cursorX, cursorY);
    lastClearPressMs = now;
  }
  joystickWasDown = joystickDown;
  clearWasDown = clearDown;
}

void setup() {
  pinMode(JOYSTICK_SWITCH_PIN, INPUT_PULLUP);
  pinMode(CLEAR_BUTTON_PIN, INPUT_PULLUP);
  pinMode(TOUCH_CS_PIN, OUTPUT);
  digitalWrite(TOUCH_CS_PIN, HIGH);
  analogReadResolution(12);

  SPI.begin(TFT_SCK_PIN, TFT_MISO_PIN, TFT_MOSI_PIN, TFT_CS_PIN);
  display.begin();
  display.setRotation(1);
  display.fillScreen(ILI9341_BLACK);
  drawStatus();
  drawCursor(cursorX, cursorY);
}

void loop() {
  readControls();
  moveCursorFromJoystick();
  delay(3);
}