Esp32TV/main/video_broadcast.c

/**
 * @file video_broadcast.c
 * @brief ESP32 Video Broadcast - RF modulation via I2S DMA
 *
 * This module generates analog NTSC/PAL television signals by outputting
 * an 80 MHz bitstream through I2S DMA. The premodulated waveforms create
 * harmonics at 61.25 MHz (Channel 3 luma) for RF broadcast.
 *
 * Key differences from ESP8266 version:
 * - Uses ESP32 I2S LCD mode for parallel output
 * - Uses GDMA (lldesc_t) instead of SLC (sdio_queue)
 * - Uses esp_intr_alloc() instead of ets_isr_attach()
 * - Uses APLL for clock generation
 *
 * Original ESP8266 version: Copyright 2015 <>< Charles Lohr
 * ESP32 Port 2024
 */

#include "video_broadcast.h"
#include "broadcast_tables.h"
#include "CbTable.h"
#include "sdkconfig.h"

#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2s_std.h"
#include "driver/gpio.h"
#include "esp_log.h"
#include "esp_attr.h"
#include "esp_timer.h"
#include "soc/i2s_reg.h"
#include "soc/i2s_struct.h"
#include "soc/gpio_sig_map.h"
#include "hal/gpio_ll.h"
#include "rom/lldesc.h"
#include "esp_rom_gpio.h"
#include "esp_private/periph_ctrl.h"
#include "esp_intr_alloc.h"
#include "soc/rtc.h"

static const char *TAG = "video_broadcast";

// Video timing constants
#ifdef CONFIG_VIDEO_PAL
    #define LINE_BUFFER_LENGTH 160
    #define SHORT_SYNC_INTERVAL    5
    #define LONG_SYNC_INTERVAL    75
    #define NORMAL_SYNC_INTERVAL  10
    #define LINE_SIGNAL_INTERVAL 150
    #define COLORBURST_INTERVAL 10
#else
    #define LINE_BUFFER_LENGTH 159
    #define SHORT_SYNC_INTERVAL    6
    #define LONG_SYNC_INTERVAL    73
    #define SERRATION_PULSE_INT   67
    #define NORMAL_SYNC_INTERVAL  12
    #define LINE_SIGNAL_INTERVAL 147
    #define COLORBURST_INTERVAL 4
#endif

#define I2SDMABUFLEN LINE_BUFFER_LENGTH
#define LINE32LEN I2SDMABUFLEN

// I2S configuration for 80 MHz output
// ESP32 can use APLL or divide from 240 MHz
// Target: 80 MHz bit clock
// Using I2S LCD mode: clock = source / (N + b/a)
// For 80 MHz from 240 MHz APB: divider = 3

// Global state
int8_t jam_color = -1;
int gframe = 0;
uint16_t framebuffer[((FBW2/4)*(FBH))*2];
uint32_t last_internal_frametime = 0;

// Internal state
static int gline = 0;
static int linescratch;
static uint8_t pixline;

// Premodulation table pointers
static const uint32_t *tablestart;
static const uint32_t *tablept;
static const uint32_t *tableend;
static uint32_t *curdma;

// DMA descriptors and buffers
static lldesc_t dma_desc[DMABUFFERDEPTH] __attribute__((aligned(4)));
static uint32_t dma_buffer[I2SDMABUFLEN * DMABUFFERDEPTH] __attribute__((aligned(4)));

// I2S interrupt handle
static intr_handle_t i2s_intr_handle = NULL;

// Timing measurement
static uint32_t systimex = 0;
static uint32_t systimein = 0;

/**
 * @brief Fill DMA buffer with premodulated waveform data
 * @param qty Number of 32-bit words to fill
 * @param color Color/level index into premodulation table
 */
static inline void IRAM_ATTR fillwith(uint16_t qty, uint8_t color)
{
    if (qty & 1) {
        *(curdma++) = tablept[color];
        tablept += PREMOD_SIZE;
    }
    qty >>= 1;
    for (linescratch = 0; linescratch < qty; linescratch++) {
        *(curdma++) = tablept[color];
        tablept += PREMOD_SIZE;
        *(curdma++) = tablept[color];
        tablept += PREMOD_SIZE;
        if (tablept >= tableend) {
            tablept = tablept - tableend + tablestart;
        }
    }
}

/**
 * @brief Short sync pulse (FT_STA)
 */
static void IRAM_ATTR FT_STA(void)
{
    pixline = 0;  // Reset framebuffer line counter
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LONG_SYNC_INTERVAL, BLACK_LEVEL);
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (SHORT_SYNC_INTERVAL + LONG_SYNC_INTERVAL + SHORT_SYNC_INTERVAL), BLACK_LEVEL);
}

/**
 * @brief Long sync pulse (FT_STB)
 */
static void IRAM_ATTR FT_STB(void)
{
#ifdef CONFIG_VIDEO_PAL
    #define FT_STB_BLACK_INTERVAL SHORT_SYNC_INTERVAL
#else
    #define FT_STB_BLACK_INTERVAL NORMAL_SYNC_INTERVAL
#endif
    fillwith(LONG_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(FT_STB_BLACK_INTERVAL, BLACK_LEVEL);
    fillwith(LONG_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (LONG_SYNC_INTERVAL + FT_STB_BLACK_INTERVAL + LONG_SYNC_INTERVAL), BLACK_LEVEL);
}

/**
 * @brief Black/blanking line (FT_B)
 */
static void IRAM_ATTR FT_B(void)
{
    fillwith(NORMAL_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(2, BLACK_LEVEL);
    fillwith(COLORBURST_INTERVAL, COLORBURST_LEVEL);
    fillwith(LINE32LEN - NORMAL_SYNC_INTERVAL - 2 - COLORBURST_INTERVAL,
             (pixline < 1) ? GRAY_LEVEL : BLACK_LEVEL);
}

/**
 * @brief Short to long sync transition (FT_SRA)
 */
static void IRAM_ATTR FT_SRA(void)
{
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LONG_SYNC_INTERVAL, BLACK_LEVEL);
#ifdef CONFIG_VIDEO_PAL
    fillwith(LONG_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (SHORT_SYNC_INTERVAL + LONG_SYNC_INTERVAL + LONG_SYNC_INTERVAL), BLACK_LEVEL);
#else
    fillwith(SERRATION_PULSE_INT, SYNC_LEVEL);
    fillwith(LINE32LEN - (SHORT_SYNC_INTERVAL + LONG_SYNC_INTERVAL + SERRATION_PULSE_INT), BLACK_LEVEL);
#endif
}

/**
 * @brief Long to short sync transition (FT_SRB)
 */
static void IRAM_ATTR FT_SRB(void)
{
#ifdef CONFIG_VIDEO_PAL
    fillwith(LONG_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(SHORT_SYNC_INTERVAL, BLACK_LEVEL);
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (LONG_SYNC_INTERVAL + SHORT_SYNC_INTERVAL + SHORT_SYNC_INTERVAL), BLACK_LEVEL);
#else
    fillwith(SERRATION_PULSE_INT, SYNC_LEVEL);
    fillwith(NORMAL_SYNC_INTERVAL, BLACK_LEVEL);
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (SERRATION_PULSE_INT + NORMAL_SYNC_INTERVAL + SHORT_SYNC_INTERVAL), BLACK_LEVEL);
#endif
}

/**
 * @brief Active video line (FT_LIN)
 */
static void IRAM_ATTR FT_LIN(void)
{
    fillwith(NORMAL_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(1, BLACK_LEVEL);
    fillwith(COLORBURST_INTERVAL, COLORBURST_LEVEL);
    fillwith(11, BLACK_LEVEL);
#define HDR_SPD (NORMAL_SYNC_INTERVAL + 1 + COLORBURST_INTERVAL + 11)

    int fframe = gframe & 1;
    uint16_t *fbs = (uint16_t*)(&framebuffer[((pixline * (FBW2/2)) + (((FBW2/2)*(FBH)) * fframe)) / 2]);

    for (linescratch = 0; linescratch < FBW2/4; linescratch++) {
        uint16_t fbb = fbs[linescratch];
        *(curdma++) = tablept[(fbb >> 0) & 15];  tablept += PREMOD_SIZE;
        *(curdma++) = tablept[(fbb >> 4) & 15];  tablept += PREMOD_SIZE;
        *(curdma++) = tablept[(fbb >> 8) & 15];  tablept += PREMOD_SIZE;
        *(curdma++) = tablept[(fbb >> 12) & 15]; tablept += PREMOD_SIZE;
        if (tablept >= tableend) {
            tablept = tablept - tableend + tablestart;
        }
    }

    fillwith(LINE32LEN - (HDR_SPD + FBW2), BLACK_LEVEL);
    pixline++;
}

/**
 * @brief End frame marker (FT_CLOSE_M)
 */
static void IRAM_ATTR FT_CLOSE_M(void)
{
#ifdef CONFIG_VIDEO_PAL
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LONG_SYNC_INTERVAL, BLACK_LEVEL);
    fillwith(SHORT_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(LINE32LEN - (SHORT_SYNC_INTERVAL + LONG_SYNC_INTERVAL + SHORT_SYNC_INTERVAL), BLACK_LEVEL);
#else
    fillwith(NORMAL_SYNC_INTERVAL, SYNC_LEVEL);
    fillwith(2, BLACK_LEVEL);
    fillwith(4, COLORBURST_LEVEL);
    fillwith(LINE32LEN - NORMAL_SYNC_INTERVAL - 6, WHITE_LEVEL);
#endif
    gline = -1;
    gframe++;

    last_internal_frametime = systimex;
    systimex = 0;
    systimein = (uint32_t)esp_timer_get_time();
}

// Line type function table
static void (*CbTable[FT_MAX_d])(void) = {
    FT_STA, FT_STB, FT_B, FT_SRA, FT_SRB, FT_LIN, FT_CLOSE_M
};

/**
 * @brief I2S DMA interrupt handler
 *
 * Called when a DMA buffer completes transmission.
 * Fills the completed buffer with the next line's data.
 */
static void IRAM_ATTR i2s_isr(void *arg)
{
    // Clear interrupt
    typeof(I2S0.int_st) status = I2S0.int_st;
    I2S0.int_clr.val = status.val;

    if (status.out_eof) {
        // Get the descriptor that just finished
        lldesc_t *finish_desc = (lldesc_t*)I2S0.out_eof_des_addr;
        curdma = (uint32_t*)finish_desc->buf;

        if (jam_color < 0) {
            // Normal operation - generate video line
            int lk = 0;
            if (gline & 1) {
                lk = (CbLookup[gline >> 1] >> 4) & 0x0f;
            } else {
                lk = CbLookup[gline >> 1] & 0x0f;
            }

            systimein = (uint32_t)esp_timer_get_time();
            CbTable[lk]();
            systimex += (uint32_t)esp_timer_get_time() - systimein;
            gline++;
        } else {
            // Jam mode - fill with single color for RF testing
            fillwith(LINE32LEN, jam_color);
        }
    }
}

/**
 * @brief Configure I2S for 80 MHz serial bitstream output
 *
 * This uses standard I2S mode (not LCD mode) to output a serial bitstream
 * on the data pin at 80 MHz. The premodulated patterns create RF harmonics
 * at Channel 3 frequency (61.25 MHz).
 */
static void configure_i2s(void)
{
    // Enable I2S peripheral
    periph_module_enable(PERIPH_I2S0_MODULE);

    // Reset I2S
    I2S0.conf.tx_reset = 1;
    I2S0.conf.tx_reset = 0;
    I2S0.conf.rx_reset = 1;
    I2S0.conf.rx_reset = 0;

    // Reset FIFO
    I2S0.conf.tx_fifo_reset = 1;
    I2S0.conf.tx_fifo_reset = 0;
    I2S0.conf.rx_fifo_reset = 1;
    I2S0.conf.rx_fifo_reset = 0;

    // Reset DMA
    I2S0.lc_conf.in_rst = 1;
    I2S0.lc_conf.in_rst = 0;
    I2S0.lc_conf.out_rst = 1;
    I2S0.lc_conf.out_rst = 0;

    // Disable LCD mode - use standard serial I2S
    I2S0.conf2.lcd_en = 0;
    I2S0.conf2.lcd_tx_wrx2_en = 0;
    I2S0.conf2.lcd_tx_sdx2_en = 0;
    I2S0.conf2.camera_en = 0;

    // Configure for serial transmission (like ESP8266)
    I2S0.conf.tx_msb_right = 0;
    I2S0.conf.tx_right_first = 0;
    I2S0.conf.tx_slave_mod = 0;  // Master mode
    I2S0.conf.tx_mono = 1;       // Mono - single channel
    I2S0.conf.tx_short_sync = 0;
    I2S0.conf.tx_msb_shift = 0;  // No shift, output raw bits

    // Configure FIFO for 32-bit mono
    I2S0.fifo_conf.tx_fifo_mod = 3;  // 32-bit single channel
    I2S0.fifo_conf.tx_fifo_mod_force_en = 1;
    I2S0.fifo_conf.dscr_en = 1;  // Enable DMA

    // Configure channel - mono mode
    I2S0.conf_chan.tx_chan_mod = 3;  // Single channel on data out

    // Configure sample bits - 32 bits per sample
    I2S0.sample_rate_conf.tx_bits_mod = 32;

    // Configure clock for 80 MHz bit clock
    // PLL_D2_CLK = 160 MHz (when CPU at 240 MHz)
    // We want BCK = 80 MHz
    // Master clock divider: 160 / 2 = 80 MHz
    // BCK divider: 1 (pass through)

    I2S0.clkm_conf.clkm_div_num = 2;   // Divide 160 MHz by 2 = 80 MHz
    I2S0.clkm_conf.clkm_div_b = 0;
    I2S0.clkm_conf.clkm_div_a = 1;
    I2S0.clkm_conf.clk_en = 1;
    I2S0.clkm_conf.clka_en = 0;  // Use PLL_D2_CLK (160 MHz)

    // BCK = MCLK / tx_bck_div_num
    // We want BCK = 80 MHz, MCLK = 80 MHz, so div = 1
    I2S0.sample_rate_conf.tx_bck_div_num = 1;

    // Don't start yet
    I2S0.conf.tx_start = 0;

    ESP_LOGI(TAG, "I2S configured: serial mode, 80 MHz target bit clock");
}

/**
 * @brief Setup DMA descriptors in circular configuration
 */
static void setup_dma_descriptors(void)
{
    for (int i = 0; i < DMABUFFERDEPTH; i++) {
        dma_desc[i].size = I2SDMABUFLEN * 4;
        dma_desc[i].length = I2SDMABUFLEN * 4;
        dma_desc[i].buf = (uint8_t*)&dma_buffer[i * I2SDMABUFLEN];
        dma_desc[i].owner = 1;
        dma_desc[i].sosf = 0;
        dma_desc[i].eof = 1;
        dma_desc[i].qe.stqe_next = (i < DMABUFFERDEPTH - 1) ?
                                   &dma_desc[i + 1] : &dma_desc[0];

        // Initialize buffer to black
        memset((void*)dma_desc[i].buf, 0, I2SDMABUFLEN * 4);
    }
}

/**
 * @brief Configure GPIO for I2S data output
 */
static void configure_gpio(void)
{
    int gpio_num = CONFIG_I2S_DATA_GPIO;

    // Configure GPIO as high-speed output
    gpio_set_direction(gpio_num, GPIO_MODE_OUTPUT);
    gpio_set_pull_mode(gpio_num, GPIO_FLOATING);

    // Set high drive strength for better RF output
    gpio_set_drive_capability(gpio_num, GPIO_DRIVE_CAP_3);

    // Route I2S0 serial data to GPIO
    // In standard I2S mode, DATA_OUT23 is the serial data (MSB first)
    esp_rom_gpio_connect_out_signal(gpio_num, I2S0O_DATA_OUT23_IDX, false, false);

    ESP_LOGI(TAG, "I2S serial data output on GPIO %d (high drive)", gpio_num);
}

void video_broadcast_init(void)
{
    ESP_LOGI(TAG, "Initializing video broadcast system");

    // Initialize table pointers
    tablestart = &premodulated_table[0];
    tablept = &premodulated_table[0];
    tableend = &premodulated_table[PREMOD_ENTRIES * PREMOD_SIZE];

    // Initialize state
    jam_color = -1;
    gframe = 0;
    gline = 0;
    pixline = 0;
    memset(framebuffer, 0, sizeof(framebuffer));

    // Configure I2S peripheral
    configure_i2s();

    // Setup DMA descriptors
    setup_dma_descriptors();

    // Configure GPIO
    configure_gpio();

    // Register interrupt handler
    esp_intr_alloc(ETS_I2S0_INTR_SOURCE,
                   ESP_INTR_FLAG_IRAM | ESP_INTR_FLAG_LEVEL1,
                   i2s_isr, NULL, &i2s_intr_handle);

    // Enable interrupt on TX EOF
    I2S0.int_ena.out_eof = 1;

    // Link DMA descriptor
    I2S0.out_link.addr = (uint32_t)&dma_desc[0];
    I2S0.out_link.start = 1;

    // Start transmission
    I2S0.conf.tx_start = 1;

    ESP_LOGI(TAG, "Video broadcast started");
#ifdef CONFIG_VIDEO_PAL
    ESP_LOGI(TAG, "Video standard: PAL (%d lines)", VIDEO_LINES);
#else
    ESP_LOGI(TAG, "Video standard: NTSC (%d lines)", VIDEO_LINES);
#endif
    ESP_LOGI(TAG, "Framebuffer: %dx%d pixels", FBW2, FBH);
}

void video_broadcast_stop(void)
{
    // Only stop if video was ever initialized
    if (!i2s_intr_handle) {
        ESP_LOGI(TAG, "Video broadcast not running");
        return;
    }

    ESP_LOGI(TAG, "Stopping video broadcast");

    // Stop transmission
    I2S0.conf.tx_start = 0;
    I2S0.out_link.stop = 1;

    // Disable interrupt
    I2S0.int_ena.out_eof = 0;

    // Free interrupt
    esp_intr_free(i2s_intr_handle);
    i2s_intr_handle = NULL;

    // Disable I2S peripheral
    periph_module_disable(PERIPH_I2S0_MODULE);

    ESP_LOGI(TAG, "Video broadcast stopped");
}

void video_broadcast_pause(void)
{
    if (i2s_intr_handle) {
        esp_intr_disable(i2s_intr_handle);
    }
}

void video_broadcast_resume(void)
{
    if (i2s_intr_handle) {
        esp_intr_enable(i2s_intr_handle);
    }
}