83+ FPS Update Without DMA

[KaliAssistant]

I am using SPI_FREQUENCY 80E6 and SPI_READ_FREQUENCY 60E6 on a recently purchased Waveshare ESP32S3-GEEK board, which has an ST7789 240x135 RGB565 TFT LCD.

By leveraging FreeRTOS, I created a task that continuously refreshes the TFT LCD at a stable 85 Hz. Due to vTask timing precision being limited to 1 ms, the actual refresh rate becomes 83.33 Hz.

Additionally, I implemented an SD card streaming system that reads an RGB565 video file at 60 FPS. The video was generated using OpenCV, where I converted each frame to PNG, then transformed them into RGB565 format and merged them into a single video.bin file.

Surprisingly, I am able to consistently achieve this high frame rate without using DMA. I am unsure why the performance remains so stable.

I will include code snippets and a video demonstration for reference.

Would love to hear thoughts or explanations on this!

IMG_5774-2.mp4

code

Setup303_WaveShare_ESP32S3_GEEK.h

// ST7789 135 x 240 display

#define USER_SETUP_ID 303

#ifdef ILI9341_DRIVER
#undef ILI9341_DRIVER
#endif
#define ST7789_DRIVER // Configure all registers

#define TFT_WIDTH  135
#define TFT_HEIGHT 240

#define CGRAM_OFFSET      // Library will add offsets required

#define TFT_RGB_ORDER TFT_BGR  // Colour order Blue-Green-Red

#define TFT_INVERSION_ON

// Generic ESP32 setup
#define TFT_MOSI 11
#define TFT_SCLK 12
#define TFT_CS    10
#define TFT_DC    8
#define TFT_RST   9
//#define TFT_BL    7


#define LOAD_GLCD   // Font 1. Original Adafruit 8 pixel font needs ~1820 bytes in FLASH
#define LOAD_FONT2  // Font 2. Small 16 pixel high font, needs ~3534 bytes in FLASH, 96 characters
#define LOAD_FONT4  // Font 4. Medium 26 pixel high font, needs ~5848 bytes in FLASH, 96 characters
#define LOAD_FONT6  // Font 6. Large 48 pixel font, needs ~2666 bytes in FLASH, only characters 1234567890:-.apm
#define LOAD_FONT7  // Font 7. 7 segment 48 pixel font, needs ~2438 bytes in FLASH, only characters 1234567890:.
#define LOAD_FONT8  // Font 8. Large 75 pixel font needs ~3256 bytes in FLASH, only characters 1234567890:-.
//#define LOAD_FONT8N // Font 8. Alternative to Font 8 above, slightly narrower, so 3 digits fit a 160 pixel TFT
#define LOAD_GFXFF  // FreeFonts. Include access to the 48 Adafruit_GFX free fonts FF1 to FF48 and custom fonts

#define SMOOTH_FONT

#define USE_HSPI_PORT
//#define ESP32_DMA

 //#define SPI_FREQUENCY  27000000
#define SPI_FREQUENCY  (int)80E6
#define SPI_READ_FREQUENCY  (int)60E6

libfb.cpp

//#define USE_DMA

// .........

void libfb::fb_xinit()
{
    if (!fb_is_init)
    {

        xTaskCreatePinnedToCore([](void *param) { auto *fbInstance = static_cast<libfb*>(param); fbInstance->_fbUpdate(param);}, "FB_UPDATE", 8192, this, 1, &_fb_update_handel, 0);
        fb_is_init=true;
    }
    else
    {
        log_e("Fr4M3 BuFf3R 1s 4lR3aDy 1N1t !");
    }

}

// ........

void libfb::fb_disp_image(int32_t x, int32_t y, int32_t w, int32_t h, uint16_t* ptr, uint16_t* data)
{
    if (x < 0 || y < 0 || (x + w) > TFT__WIDTH || (y + h) > TFT__HEIHT) 
    {
        return; // Exit if the area is out of bounds
    }
    int32_t data_pos = 0;
    for (int32_t i = 0; i < h; i++) 
    {
        for (int32_t j = 0; j < w; j++) 
        {
            // Calculate the 1D position in the image_data buffer
            int32_t pos = (y + i) * TFT__WIDTH + (x + j);
            ptr[pos] = data[data_pos++];
        }
    }
}

//......

void libfb::_fbUpdate(void* parameter)
{
    if (this == nullptr) 
    {
        log_e("this->nullptr!!!");
        return;
    }
    int64_t prevTime = esp_timer_get_time();  // Get initial timestamp (µs)
    const int TARGET_FPS = 85;  // Target frame rate
    int64_t FRAME_TIME_US = (1000000.0 / TARGET_FPS);  // Target frame time (µs)
    for(;;)
    {
        int64_t currentTime = esp_timer_get_time();
        int64_t elapsedTime = currentTime - prevTime;
        if (elapsedTime >= FRAME_TIME_US)
        {
            prevTime = currentTime;
            fb_update_frame_time = elapsedTime;
            if (rel_frameBuffer != nullptr && frameBuffer != nullptr) 
            {
               
                #ifdef USE_DMA
                uint32_t frameStart = millis();  // Start frame timer
                LCD.startWrite();
                //LCD.dmaWait();
                //LCD.setSwapBytes(true);
                LCD.pushImageDMA(0, 0, 240, 135, frameBuffer); // Initiate DMA - blocking only if last DMA is not complete
                LCD.endWrite();
                uint32_t frameDuration = millis() - frameStart;
                frame_delay_time = frameDuration;
                // The DMA transfer of image block to the TFT is now in progress...
                #else
                // Non-DMA blocking alternative
                uint32_t frameStart = millis();  // Start frame timer
                LCD.pushImage(0, 0, 240, 135, frameBuffer);  // Blocking, so only returns when image block is drawn
                uint32_t frameDuration = millis() - frameStart;
                frame_delay_time = frameDuration;
                #endif
            }
        }
        vTaskDelay(1);
    }
}

main.cpp

TaskHandle_t TEST_FB_VIDEO_TESK1_Handle = NULL;
// ......
 void setup() {
    fb.fb_xinit();
    xTaskCreate(TEST_FB_VIDEO_TESK1, "TEST_TASK_1", 66600, NULL, 1, &TEST_FB_VIDEO_TESK1_Handle);

//....
}

void TEST_FB_VIDEO_TESK1(void* parameter)
{
  int64_t prevTime = esp_timer_get_time();  // Get initial timestamp (µs)
  const int TARGET_FPS = 60;  // Target frame rate
  int64_t FRAME_TIME_US = (1000 / TARGET_FPS)*1000;  // Target frame time (µs)
  //const int TARGET_FPS = 60;  // Target frame rate
  //const int FRAME_TIME_MS = 1000 / TARGET_FPS;  // Target frame time (ms)

  // Allocate buffer once to avoid malloc/free overhead
  
  uint16_t *buffer = (uint16_t*) heap_caps_malloc(TFT__WIDTH * TFT__HEIHT * sizeof(uint16_t), MALLOC_CAP_SPIRAM);
  if (!buffer) {
    SerialUSB.println("Memory allocation failed!");
    vTaskDelete(NULL);
    return;
  }
  for(;;)
  {
    
    failSD:
    // Wait for SD card insertion
    HotPlugSD.checkCardStatus();
    while (!HotPlugSD.isCardInserted()) {
      SerialUSB.println("SD card missing. Halting...");
      vTaskDelay(pdMS_TO_TICKS(500));  // Check every 500ms
    }

    //uint32_t prevTime = millis();  // Get initial timestamp (µs)

    fs::File video_file = HotPlugSD.open("/video.bin", "r");
    if (!video_file) 
    {
      SerialUSB.println("Failed to open video file. Retrying...");
      vTaskDelay(pdMS_TO_TICKS(500));  // Retry after delay
      continue;
    }
    int i=0;
      
    while (video_file.available())
    {
      /* code */
      int64_t currentTime = esp_timer_get_time();
      int64_t elapsedTime = currentTime - prevTime;
      if (elapsedTime >= FRAME_TIME_US)
      {
        prevTime = currentTime;
        int bytesRead = video_file.read((uint8_t *)buffer, TFT__WIDTH * TFT__HEIHT * sizeof(uint16_t));  // Fast read
        if (bytesRead != TFT__WIDTH * TFT__HEIHT * sizeof(uint16_t)) goto failSD;
        fb.fb_disp_image(0, 0, 240, 135, fb.frameBuffer, buffer);  // Display frame

        // Measure and print actual FPS every 10 frames
        if (i % 10 == 0) 
        {
          SerialUSB.printf("Actual SOFT FPS: %lf\t TFTLCD PUSH TIME: %u ms\t TFTLCD UPDATE TIME: %lld us\t TFTLCD ACTUAL HZ: %lf\n", 1000000.0 / elapsedTime, fb.frame_delay_time, fb.fb_update_frame_time, 1000000.0 / fb.fb_update_frame_time);
        }

        // Check if SD card was removed mid-playback
        if (!HotPlugSD.isCardInserted()) {
          SerialUSB.println("SD card removed. Halting playback.");
          video_file.close();
          while (!HotPlugSD.isCardInserted()) 
          {
            SerialUSB.println("Waiting for SD card...");
            vTaskDelay(pdMS_TO_TICKS(500));
          }

          if (!reinitializeSD()) 
          {
            SerialUSB.println("Failed to reinitialize SD card.");
            continue;  // Restart loop
          }
        }
        i++;

      }
      vTaskDelay(1);
        //ets_delay_us(1);
    }
    video_file.close();
    vTaskDelay(pdMS_TO_TICKS(10)); 
  }
  heap_caps_free(buffer);
  
  vTaskDelete(NULL);
}