接前一篇文章：ESP32-S3模组上跑通esp32-camera（9）
本文内容参考：
esp32-camera入门（基于ESP-IDF）_esp32 camera-CSDN博客
ESP32_CAM CameraWebServer例程源码解析笔记（一）_void startcameraserver();-CSDN博客
特此致谢！
一、OV5640初始化
1. 配置接线和驱动
#include "esp_camera.h"
//WROVER-KIT PIN Map
#define CAM_PIN_PWDN -1 //power down is not used
#define CAM_PIN_RESET -1 //software reset will be performed
#define CAM_PIN_XCLK 21
#define CAM_PIN_SIOD 26
#define CAM_PIN_SIOC 27
#define CAM_PIN_D7 35
#define CAM_PIN_D6 34
#define CAM_PIN_D5 39
#define CAM_PIN_D4 36
#define CAM_PIN_D3 19
#define CAM_PIN_D2 18
#define CAM_PIN_D1 5
#define CAM_PIN_D0 4
#define CAM_PIN_VSYNC 25
#define CAM_PIN_HREF 23
#define CAM_PIN_PCLK 22
static camera_config_t camera_config = {
.pin_pwdn = CAM_PIN_PWDN,
.pin_reset = CAM_PIN_RESET,
.pin_xclk = CAM_PIN_XCLK,
.pin_sccb_sda = CAM_PIN_SIOD,
.pin_sccb_scl = CAM_PIN_SIOC,
.pin_d7 = CAM_PIN_D7,
.pin_d6 = CAM_PIN_D6,
.pin_d5 = CAM_PIN_D5,
.pin_d4 = CAM_PIN_D4,
.pin_d3 = CAM_PIN_D3,
.pin_d2 = CAM_PIN_D2,
.pin_d1 = CAM_PIN_D1,
.pin_d0 = CAM_PIN_D0,
.pin_vsync = CAM_PIN_VSYNC,
.pin_href = CAM_PIN_HREF,
.pin_pclk = CAM_PIN_PCLK,
.xclk_freq_hz = 20000000,//EXPERIMENTAL: Set to 16MHz on ESP32-S2 or ESP32-S3 to enable EDMA mode
.ledc_timer = LEDC_TIMER_0,
.ledc_channel = LEDC_CHANNEL_0,
.pixel_format = PIXFORMAT_JPEG,//YUV422,GRAYSCALE,RGB565,JPEG
.frame_size = FRAMESIZE_UXGA,//QQVGA-UXGA, For ESP32, do not use sizes above QVGA when not JPEG. The performance of the ESP32-S series has improved a lot, but JPEG mode always gives better frame rates.
.jpeg_quality = 12, //0-63, for OV series camera sensors, lower number means higher quality
.fb_count = 1, //When jpeg mode is used, if fb_count more than one, the driver will work in continuous mode.
.grab_mode = CAMERA_GRAB_WHEN_EMPTY//CAMERA_GRAB_LATEST. Sets when buffers should be filled
};
esp_err_t camera_init(){
//power up the camera if PWDN pin is defined
if(CAM_PIN_PWDN != -1){
pinMode(CAM_PIN_PWDN, OUTPUT);
digitalWrite(CAM_PIN_PWDN, LOW);
}
//initialize the camera
esp_err_t err = esp_camera_init(&camera_config);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Camera Init Failed");
return err;
}
return ESP_OK;
}
esp_err_t camera_capture(){
//acquire a frame
camera_fb_t * fb = esp_camera_fb_get();
if (!fb) {
ESP_LOGE(TAG, "Camera Capture Failed");
return ESP_FAIL;
}
//replace this with your own function
process_image(fb->width, fb->height, fb->format, fb->buf, fb->len);
//return the frame buffer back to the driver for reuse
esp_camera_fb_return(fb);
return ESP_OK;
}上一回讲解了camera_config_t中与图像质量和帧缓冲相关的成员，本回继续解析其它成员。为了便于理解和回顾，再次贴出camera_config_t的定义，在components\esp32-camera\driver\include\esp_camera.h中，如下：
/**
* @brief Configuration structure for camera initialization
*/
typedef struct {
int pin_pwdn; /*!< GPIO pin for camera power down line */
int pin_reset; /*!< GPIO pin for camera reset line */
int pin_xclk; /*!< GPIO pin for camera XCLK line */
union {
int pin_sccb_sda; /*!< GPIO pin for camera SDA line */
int pin_sscb_sda __attribute__((deprecated("please use pin_sccb_sda instead"))); /*!< GPIO pin for camera SDA line (legacy name) */
};
union {
int pin_sccb_scl; /*!< GPIO pin for camera SCL line */
int pin_sscb_scl __attribute__((deprecated("please use pin_sccb_scl instead"))); /*!< GPIO pin for camera SCL line (legacy name) */
};
int pin_d7; /*!< GPIO pin for camera D7 line */
int pin_d6; /*!< GPIO pin for camera D6 line */
int pin_d5; /*!< GPIO pin for camera D5 line */
int pin_d4; /*!< GPIO pin for camera D4 line */
int pin_d3; /*!< GPIO pin for camera D3 line */
int pin_d2; /*!< GPIO pin for camera D2 line */
int pin_d1; /*!< GPIO pin for camera D1 line */
int pin_d0; /*!< GPIO pin for camera D0 line */
int pin_vsync; /*!< GPIO pin for camera VSYNC line */
int pin_href; /*!< GPIO pin for camera HREF line */
int pin_pclk; /*!< GPIO pin for camera PCLK line */
int xclk_freq_hz; /*!< Frequency of XCLK signal, in Hz. EXPERIMENTAL: Set to 16MHz on ESP32-S2 or ESP32-S3 to enable EDMA mode */
ledc_timer_t ledc_timer; /*!< LEDC timer to be used for generating XCLK */
ledc_channel_t ledc_channel; /*!< LEDC channel to be used for generating XCLK */
pixformat_t pixel_format; /*!< Format of the pixel data: PIXFORMAT_ + YUV422|GRAYSCALE|RGB565|JPEG */
framesize_t frame_size; /*!< Size of the output image: FRAMESIZE_ + QVGA|CIF|VGA|SVGA|XGA|SXGA|UXGA */
int jpeg_quality; /*!< Quality of JPEG output. 0-63 lower means higher quality */
size_t fb_count; /*!< Number of frame buffers to be allocated. If more than one, then each frame will be acquired (double speed) */
camera_fb_location_t fb_location; /*!< The location where the frame buffer will be allocated */
camera_grab_mode_t grab_mode; /*!< When buffers should be filled */
#if CONFIG_CAMERA_CONVERTER_ENABLED
camera_conv_mode_t conv_mode; /*!< RGB<->YUV Conversion mode */
#endif
int sccb_i2c_port; /*!< If pin_sccb_sda is -1, use the already configured I2C bus by number */
} camera_config_t;接下来关注以下成员：
typedef struct {
……
camera_grab_mode_t grab_mode; /*!< When buffers should be filled */
#if CONFIG_CAMERA_CONVERTER_ENABLED
camera_conv_mode_t conv_mode; /*!< RGB<->YUV Conversion mode */
#endif
int sccb_i2c_port; /*!< If pin_sccb_sda is -1, use the already configured I2C bus by number */
……
} camera_config_t;- camera_grab_mode_t grab_mode
设置图像数据的抓取模式。上边示例代码中设置为CAMERA_GRAB_WHEN_EMPTY，表示在缓冲区为空时抓取图像。
.grab_mode = CAMERA_GRAB_WHEN_EMPTY//CAMERA_GRAB_LATEST. Sets when buffers should be filledcamera_grab_mode_t的定义在components\esp32-camera\driver\include\esp_camera.h中，如下：
/**
* @brief Configuration structure for camera initialization
*/
typedef enum {
CAMERA_GRAB_WHEN_EMPTY, /*!< Fills buffers when they are empty. Less resources but first 'fb_count' frames might be old */
CAMERA_GRAB_LATEST /*!< Except when 1 frame buffer is used, queue will always contain the last 'fb_count' frames */
} camera_grab_mode_t;可见，camera_grab_mode_t为枚举类型，包含了两个枚举值：
- CAMERA_GRAB_WHEN_EMPTY：当缓冲区为空时填充缓冲区。（占用）资源更少，但第一个“fb_count”帧可能是旧的。
- CAMERA_GRAB_LATEST：除非使用1帧缓冲区，否则队列将始终包含最后的“fb_count”帧。
- camera_conv_mode_t conv_mode
RGB<->YUV转换模式。上边示例代码中并为赋值。注意，此成员是有条件的，必须在CONFIG_CAMERA_CONVERTER_ENABLED宏为非零值的时候才会存在。
camera_conv_mode_t的定义在components\esp32-camera\driver\include\esp_camera.h中，如下：
#if CONFIG_CAMERA_CONVERTER_ENABLED
/**
* @brief Camera RGB\YUV conversion mode
*/
typedef enum {
CONV_DISABLE,
RGB565_TO_YUV422,
YUV422_TO_RGB565,
YUV422_TO_YUV420
} camera_conv_mode_t;
#endifCONFIG_CAMERA_CONVERTER_ENABLED是在menuconfig中定义的，默认并不选择。
- int sccb_i2c_port
如果pin_sccb_sda为-1，则按编号使用已配置的I2C总线。
至此，camera_config_t结构及其实例camera_config的最后一段代码就解析完了，整个结构体也就都讲解完了。下一回开始正式解析函数代码。
标签：10,PIN,pin,S3,esp32,int,camera,mode,CAM From： https://blog.csdn.net/phmatthaus/article/details/143635415