Portable ESP32 Laptop

#include <Arduino.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_ILI9341.h>
#include <XPT2046_Touchscreen.h>


// Forward declarations
void drawLine(uint8_t line);
void drawCursor();
void redrawNote();
void clearNote();
void newLine();
void appendCharacter(char key);
char readKeyboard();

constexpr uint8_t TFT_CS_PIN = 17;
constexpr uint8_t TFT_DC_PIN = 6;
constexpr uint8_t TFT_RST_PIN = 7;
constexpr uint8_t TOUCH_CS_PIN = 8;
constexpr uint8_t TFT_MOSI_PIN = 19;
constexpr uint8_t TFT_MISO_PIN = 16;
constexpr uint8_t TFT_SCK_PIN = 18;
constexpr uint8_t KEYBOARD_SDA_PIN = 4;
constexpr uint8_t KEYBOARD_SCL_PIN = 5;
constexpr uint8_t KEYBOARD_ADDRESS = 0x5F;

constexpr int16_t SCREEN_W = 320;
constexpr int16_t SCREEN_H = 240;
constexpr int16_t HEADER_H = 26;
constexpr int16_t FOOTER_H = 18;
constexpr int16_t TEXT_X = 8;
constexpr int16_t TEXT_Y = 36;
constexpr int16_t CHAR_W = 6;
constexpr int16_t LINE_H = 10;
constexpr uint8_t MAX_COLS = 50;
constexpr uint8_t MAX_LINES = 18;
constexpr uint16_t HEADER_COLOR = 0x000F;
constexpr uint16_t FOOTER_COLOR = 0x7BEF;

Adafruit_ILI9341 tft(TFT_CS_PIN, TFT_DC_PIN, TFT_RST_PIN);
XPT2046_Touchscreen touch(TOUCH_CS_PIN);
char noteLines[MAX_LINES][MAX_COLS + 1];
uint8_t cursorLine = 0;
uint8_t cursorCol = 0;
unsigned long lastKeyPoll = 0;
unsigned long lastTouchPoll = 0;

void drawLine(uint8_t line) {
  const int16_t y = TEXT_Y + line * LINE_H;
  tft.fillRect(0, y, SCREEN_W, LINE_H, ILI9341_BLACK);
  tft.setTextColor(ILI9341_GREEN, ILI9341_BLACK);
  tft.setTextSize(1);
  tft.setCursor(TEXT_X, y + 1);
  tft.print(noteLines[line]);
}

void drawCursor() {
  const int16_t x = TEXT_X + cursorCol * CHAR_W;
  const int16_t y = TEXT_Y + cursorLine * LINE_H;
  tft.drawFastVLine(x, y, LINE_H - 1, ILI9341_YELLOW);
}

void redrawNote() {
  tft.fillRect(0, HEADER_H, SCREEN_W, SCREEN_H - HEADER_H - FOOTER_H, ILI9341_BLACK);
  for (uint8_t line = 0; line < MAX_LINES; line++) drawLine(line);
  drawCursor();
}

void clearNote() {
  for (uint8_t line = 0; line < MAX_LINES; line++) noteLines[line][0] = '\0';
  cursorLine = 0;
  cursorCol = 0;
  redrawNote();
}

void newLine() {
  if (cursorLine < MAX_LINES - 1) {
    cursorLine++;
    cursorCol = 0;
    drawCursor();
  }
}

void appendCharacter(char key) {
  if (key == '\r' || key == '\n') {
    newLine();
    return;
  }
  if (key == 8 || key == 127) {
    if (cursorCol > 0) {
      cursorCol--;
      noteLines[cursorLine][cursorCol] = '\0';
      drawLine(cursorLine);
      drawCursor();
    }
    return;
  }
  if (key < 32 || key > 126) return;
  if (cursorCol >= MAX_COLS) newLine();
  if (cursorCol < MAX_COLS) {
    noteLines[cursorLine][cursorCol++] = key;
    noteLines[cursorLine][cursorCol] = '\0';
    drawLine(cursorLine);
    drawCursor();
  }
}

char readKeyboard() {
  Wire.beginTransmission(KEYBOARD_ADDRESS);
  if (Wire.endTransmission() != 0) return 0;
  if (Wire.requestFrom((int)KEYBOARD_ADDRESS, 1) != 1) return 0;
  return (char)Wire.read();
}

void setup() {
#if defined(ARDUINO_ARCH_RP2040)
  // Route the Pico 2 W hardware buses to the pins used by this build.
  SPI.setSCK(TFT_SCK_PIN);
  SPI.setTX(TFT_MOSI_PIN);
  SPI.setRX(TFT_MISO_PIN);
#endif
  SPI.begin();
  Wire.begin();
  Wire.setClock(100000);

  tft.begin();
  tft.setRotation(1);
  touch.begin();
  touch.setRotation(1);
  tft.fillScreen(ILI9341_BLACK);
  tft.fillRect(0, 0, SCREEN_W, HEADER_H, HEADER_COLOR);
  tft.setTextColor(ILI9341_WHITE, HEADER_COLOR);
  tft.setTextSize(2);
  tft.setCursor(8, 5);
  tft.print("Pocket Writer");
  tft.fillRect(0, SCREEN_H - FOOTER_H, SCREEN_W, FOOTER_H, FOOTER_COLOR);
  tft.setTextColor(ILI9341_WHITE, FOOTER_COLOR);
  tft.setTextSize(1);
  tft.setCursor(8, SCREEN_H - FOOTER_H + 5);
  tft.print("Type on keyboard | Touch screen to clear");
  clearNote();
}

void loop() {
  const unsigned long now = millis();
  if (now - lastKeyPoll >= 25) {
    lastKeyPoll = now;
    const char key = readKeyboard();
    if (key != 0) appendCharacter(key);
  }
  if (now - lastTouchPoll >= 50) {
    lastTouchPoll = now;
    if (touch.touched()) {
      clearNote();
      delay(200);
    }
  }
}