Character LCD 제어 — HD44780·4-bit Mode·Custom Char

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MCU GPIO            LCD
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─────────           ────
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PA0 ────────────► RS
4
GND ────────────► RW    (write only)
5
PA1 ────────────► E
6
PB0-3 ──────────► DB4-7
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GND ────────────► DB0-3
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+5V + 10k pot ──► VO    (contrast)

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Line 1: 0x00 ~ 0x0F   (16 chars)
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Line 2: 0x40 ~ 0x4F
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Cursor → row R, col C:
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  addr = (R ? 0x40 : 0x00) + C
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  command: 0x80 | addr

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// PA0=RS, PA1=E, PB0-3=D4-D7
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#define LCD_RS_PORT  GPIOA
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#define LCD_RS_PIN   0
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#define LCD_E_PORT   GPIOA
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#define LCD_E_PIN    1
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#define LCD_D_PORT   GPIOB
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#define LCD_D_SHIFT  0   // D4 = PB0
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static void lcd_write4(uint8_t nibble) {
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    LCD_D_PORT->BSRR = (0xFu << (LCD_D_SHIFT + 16))     // clear
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                     | ((nibble & 0xF) << LCD_D_SHIFT); // set
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    LCD_E_PORT->BSRR = (1u << LCD_E_PIN);    // E high
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    delay_us(1);                              // ≥ 230 ns
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    LCD_E_PORT->BSRR = (1u << (LCD_E_PIN + 16));   // E low
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    delay_us(1);                              // ≥ 500 ns
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}
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static void lcd_send(uint8_t byte, int rs) {
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    if (rs) LCD_RS_PORT->BSRR = (1u << LCD_RS_PIN);
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    else    LCD_RS_PORT->BSRR = (1u << (LCD_RS_PIN + 16));
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    lcd_write4(byte >> 4);
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    lcd_write4(byte & 0xF);
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    delay_us(40);   // command execution time
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}
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void lcd_cmd(uint8_t cmd)  { lcd_send(cmd, 0); }
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void lcd_data(uint8_t data) { lcd_send(data, 1); }

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void lcd_init(void) {
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    // GPIO init (RS, E, D4-D7)
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    gpio_init(GPIOA, 0, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT});
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    gpio_init(GPIOA, 1, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT});
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    for (int i = 0; i < 4; i++)
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        gpio_init(GPIOB, i, &(gpio_config_t){.mode=GPIO_MODE_OUTPUT});
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    delay_ms(50);                  // power-on wait > 40 ms
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    // Function set sequence (8-bit mode first, then switch to 4-bit)
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    lcd_write4(0x3); delay_ms(5);
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    lcd_write4(0x3); delay_us(100);
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    lcd_write4(0x3); delay_us(100);
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    lcd_write4(0x2);                // switch to 4-bit
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    lcd_cmd(0x28);                  // 4-bit, 2 line, 5x8 font
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    lcd_cmd(0x0C);                  // display ON, cursor OFF
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    lcd_cmd(0x01); delay_ms(2);     // clear
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    lcd_cmd(0x06);                  // entry mode: cursor++, no shift
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}
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void lcd_clear(void) {
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    lcd_cmd(0x01);
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    delay_ms(2);
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}
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void lcd_goto(uint8_t row, uint8_t col) {
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    uint8_t addr = (row ? 0x40 : 0x00) + col;
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    lcd_cmd(0x80 | addr);
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}
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void lcd_print(const char *s) {
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    while (*s) lcd_data(*s++);
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}

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void lcd_define_char(uint8_t code, const uint8_t pattern[8]) {
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    lcd_cmd(0x40 | (code * 8));   // CGRAM address
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    for (int i = 0; i < 8; i++)
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        lcd_data(pattern[i]);
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}
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const uint8_t heart[8] = {
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    0b00000, 0b01010, 0b11111, 0b11111,
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    0b11111, 0b01110, 0b00100, 0b00000,
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};
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void demo(void) {
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    lcd_define_char(0, heart);
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    lcd_clear();
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    lcd_goto(0, 0);
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    lcd_print("Hello LCD ");
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    lcd_data(0);                 // ♥
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}

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// I2C address 0x27 (typical)
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#define LCD_I2C_ADDR  0x27
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static uint8_t bl = 0x08;   // backlight bit (P3)
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static void lcd_i2c_write(uint8_t nibble, int rs) {
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    uint8_t v = (nibble & 0xF0) | bl | (rs ? 0x01 : 0) | 0x04;  // E high
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    i2c_write(LCD_I2C_ADDR, &v, 1);
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    delay_us(1);
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    v &= ~0x04;                 // E low
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    i2c_write(LCD_I2C_ADDR, &v, 1);
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    delay_us(50);
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}
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void lcd_send_i2c(uint8_t byte, int rs) {
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    lcd_i2c_write(byte & 0xF0, rs);
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    lcd_i2c_write((byte << 4) & 0xF0, rs);
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}