TFT 디스플레이 구동 — RGB565·FSMC·LTDC·DMA2D

1
RGB565 = ((R >> 3) << 11) | ((G >> 2) << 5) | (B >> 3)

1
Single buffer:    뜸. tearing 발생.
2
Double buffer:    front + back. back 그리고 vsync에 swap. 메모리 ×2.
3
Tear-free single: vsync 신호 기다린 후 update.

1
// CS=PA4, DC=PA3, RES=PA2, SPI1
2
static void tft_cmd(uint8_t cmd) {
3
    GPIOA->BSRR = (1u << (3+16));   // DC=0
4
    GPIOA->BSRR = (1u << (4+16));   // CS=0
5
    spi_xfer8(cmd);
6
    while (SPI1->SR & SPI_SR_BSY);
7
    GPIOA->BSRR = (1u << 4);
8
}
9

10
static void tft_data(const uint8_t *data, uint16_t n) {
11
    GPIOA->BSRR = (1u << 3);
12
    GPIOA->BSRR = (1u << (4+16));
13
    for (uint16_t i = 0; i < n; i++) spi_xfer8(data[i]);
14
    while (SPI1->SR & SPI_SR_BSY);
15
    GPIOA->BSRR = (1u << 4);
16
}
17

18
void tft_init(void) {
19
    // Hardware reset
20
    GPIOA->BSRR = (1u << (2+16));
21
    delay_ms(10);
22
    GPIOA->BSRR = (1u << 2);
23
    delay_ms(150);
24

25
    tft_cmd(0x01); delay_ms(150);     // software reset
26
    tft_cmd(0x11); delay_ms(120);     // sleep out
27

28
    tft_cmd(0x3A); tft_data((uint8_t[]){0x55}, 1);   // 16-bit color
29
    tft_cmd(0x36); tft_data((uint8_t[]){0x48}, 1);   // MADCTL: BGR
30
    tft_cmd(0x29);                                    // display ON
31
}
32

33
void tft_set_window(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1) {
34
    tft_cmd(0x2A);
35
    tft_data((uint8_t[]){x0 >> 8, x0, x1 >> 8, x1}, 4);
36
    tft_cmd(0x2B);
37
    tft_data((uint8_t[]){y0 >> 8, y0, y1 >> 8, y1}, 4);
38
    tft_cmd(0x2C);   // memory write
39
}
40

41
void tft_pixel(uint16_t x, uint16_t y, uint16_t color) {
42
    tft_set_window(x, y, x, y);
43
    uint8_t buf[2] = {color >> 8, color};
44
    tft_data(buf, 2);
45
}
46

47
void tft_fill(uint16_t color) {
48
    tft_set_window(0, 0, 239, 319);
49
    GPIOA->BSRR = (1u << 3);
50
    GPIOA->BSRR = (1u << (4+16));
51
    for (uint32_t i = 0; i < 240u * 320; i++) {
52
        spi_xfer8(color >> 8);
53
        spi_xfer8(color);
54
    }
55
    GPIOA->BSRR = (1u << 4);
56
}

1
#define LCD_W 480
2
#define LCD_H 272
3
#define SDRAM_BASE 0xD0000000UL
4
static volatile uint16_t *fb = (uint16_t *)SDRAM_BASE;
5

6
void ltdc_init(void) {
7
    RCC->APB2ENR |= RCC_APB2ENR_LTDCEN;
8

9
    // PLLSAI: LTDC clock = 9 MHz (60 Hz refresh on 480x272)
10
    // ... PLLSAI 설정 생략
11

12
    // Timing
13
    LTDC->SSCR = ((41 - 1) << 16) | (10 - 1);     // sync size
14
    LTDC->BPCR = ((43 - 1) << 16) | (12 - 1);     // back porch
15
    LTDC->AWCR = ((480+43-1) << 16) | (272+12-1); // active width
16
    LTDC->TWCR = ((480+43+8-1) << 16) | (272+12+4-1); // total
17

18
    LTDC->GCR = LTDC_GCR_LTDCEN;
19

20
    // Layer 1
21
    LTDC_Layer1->WHPCR = ((480+43) << 16) | (43+1);
22
    LTDC_Layer1->WVPCR = ((272+12) << 16) | (12+1);
23
    LTDC_Layer1->PFCR  = 2;                       // RGB565
24
    LTDC_Layer1->CFBAR = (uint32_t)fb;
25
    LTDC_Layer1->CFBLR = ((480*2) << 16) | (480*2 + 3);
26
    LTDC_Layer1->CFBLNR = 272;
27
    LTDC_Layer1->CR    = LTDC_LxCR_LEN;
28

29
    LTDC->SRCR = LTDC_SRCR_IMR;   // reload
30
}
31

32
void ltdc_pixel(uint16_t x, uint16_t y, uint16_t color) {
33
    fb[y * LCD_W + x] = color;
34
}
35

36
void ltdc_fill(uint16_t color) {
37
    for (uint32_t i = 0; i < LCD_W * LCD_H; i++) fb[i] = color;
38
}

1
static volatile uint16_t *fb_front = (uint16_t *)SDRAM_BASE;
2
static volatile uint16_t *fb_back  = (uint16_t *)(SDRAM_BASE + LCD_W * LCD_H * 2);
3

4
static volatile int swap_pending;
5

6
void ltdc_swap(void) {
7
    swap_pending = 1;
8
    // wait for vsync ISR
9
    while (swap_pending);
10
}
11

12
void LTDC_IRQHandler(void) {
13
    if (LTDC->ISR & LTDC_ISR_LIF) {
14
        LTDC->ICR = LTDC_ICR_CLIF;
15
        if (swap_pending) {
16
            volatile uint16_t *tmp = fb_front;
17
            fb_front = fb_back;
18
            fb_back  = tmp;
19
            LTDC_Layer1->CFBAR = (uint32_t)fb_front;
20
            LTDC->SRCR = LTDC_SRCR_VBR;   // shadow reload on vsync
21
            swap_pending = 0;
22
        }
23
    }
24
}

1
VSYNC: 60 Hz (16.7 ms 주기)
2
HSYNC: 60 × (272+12+4+12) = 18 kHz
3
DE:    active 영역에서 high