Concepts First
- DVP: a parallel camera interface with many data lines and hsync/vsync signals for fast image transfer.
- Sensor: the camera's core chip (e.g. GC0308), configured over I2C; the example auto-scans to identify it.
- Crop: takes only part of the frame (416×240 here) to reduce processing, useful when only a region matters.
Example Overview
This page is based on the cam_crop example in the official Bouffalo SDK (examples/peripherals/cam/cam_crop), which demonstrates DVP camera capture with cropping:
- Auto-scans and identifies the image sensor over I2C (
image_sensor_scan); - Crops the picture to 416×240 with
bflb_cam_crop_hsync/vsync; - Configures the DMA output buffer, starts capture, and loops pulling frames (
bflb_cam_get_frame_count/get_frame_info/pop_one_frame) for 50 frames. - Sibling examples (
examples/peripherals/cam/):cam_normal(normal capture),cam_int(interrupt mode),cam_yuv420(YUV420 output),cam_lcd(camera to LCD display).
Operation Steps
Connect a DVP-interface camera module (the sensor is configured over I2C). Wire the DVP data/clock/hsync/vsync lines per board_dvp_gpio_init(), the camera I2C to I2C0, and power at 3.3V.
Open a terminal and enter the CAM example directory (prerequisite: set up the environment as in Quick Start (Linux) or Windows):
cd examples/peripherals/cam/cam_cropRun the build command. The Ai-M62 (BL616) and Ai-M61 (BL618) belong to the same series, so both use bl616:
make CHIP=bl616 BOARD=bl616dkConnect the board with a USB cable, hold the BOOT button (IO2 on the Ai-M61-32S-Kit), briefly press EN/RST to enter download mode, then flash (replace the serial port with the one on your computer):
make flash CHIP=bl616 COMX=/dev/ttyUSB0Open a serial tool (baud rate 2000000). The example scans and prints the sensor model (Sensor name: xxx), then captures 50 frames at a cropped 416×240 resolution, printing frame info per frame, and finally loops forever.
Code Execution Flow
The complete execution flow from startup to running is shown below (loop arrows mean repeated execution):
APIs Used by the Example
image_sensor_scan(i2c0, &sensor_config)
Scans and identifies the camera sensor over I2C, returning its config (resolution, register init sequence).
Parameters:
i2c: I2C device handlesensor_config:struct image_sensor_config_s *output
Return: 1 on success; 0 on failure
bflb_cam_crop_hsync / bflb_cam_crop_vsync(cam, start, end)
Sets the horizontal/vertical crop range (must be called before bflb_cam_init).
Parameters:
cam: CAM device handle (bflb_device_get_by_name("cam0"))start/end: crop start/end pixels
Return: 0 on success; negative error code on failure
bflb_cam_init / bflb_cam_start(...)
Initializes CAM per config (DVP input, output format/buffer) and starts capture.
Parameters: struct bflb_cam_config_s config
Return: 0 on success; negative error code on failure
bflb_cam_get_frame_count / get_frame_info / pop_one_frame(...)
Checks available frames, gets the frame data pointer/size, and pops the processed frame for continuous capture.
Parameters: CAM device handle, frame info outputs
Return: 0 on success; frame info via output params
Complete Code
The complete source below matches the effect described on this page. It is based on the official example (examples/peripherals/cam/cam_crop); the LED pins are adapted to the Ai-M61/62-32S-Kit onboard RGB LED. Collapsed by default, click to expand:
📜 Click to expand cam_crop/main.c full code
#include "bflb_mtimer.h"
#include "bflb_i2c.h"
#include "bflb_cam.h"
#include "image_sensor.h"
#include "board.h"
#include "malloc.h"
#define CROP_WQVGA_X 416
#define CROP_WQVGA_Y 240
#define CAM_OUTPUT_BUFFER_SIZE (CROP_WQVGA_X * CROP_WQVGA_Y * 2 * 2)
#define CAM_FRAME_COUNT_USE 50
static struct bflb_device_s *i2c0;
static struct bflb_device_s *cam0;
int main(void)
{
uint32_t i, pic_size;
uint8_t *pic;
struct bflb_cam_config_s cam_config;
struct image_sensor_config_s *sensor_config;
board_init();
board_dvp_gpio_init();
i2c0 = bflb_device_get_by_name("i2c0");
cam0 = bflb_device_get_by_name("cam0");
if (image_sensor_scan(i2c0, &sensor_config)) {
printf("\r\nSensor name: %s\r\n", sensor_config->name);
} else {
printf("\r\nError! Can't identify sensor!\r\n");
while (1) {}
}
/* Crop resolution_x, should be set before init */
bflb_cam_crop_hsync(cam0, 112, 112 + CROP_WQVGA_X);
/* Crop resolution_y, should be set before init */
bflb_cam_crop_vsync(cam0, 120, 120 + CROP_WQVGA_Y);
memcpy(&cam_config, sensor_config, IMAGE_SENSOR_INFO_COPY_SIZE);
cam_config.with_mjpeg = false;
cam_config.input_source = CAM_INPUT_SOURCE_DVP;
cam_config.output_format = CAM_OUTPUT_FORMAT_AUTO;
cam_config.output_bufaddr = (uint32_t)memalign(32, CAM_OUTPUT_BUFFER_SIZE);
if (cam_config.output_bufaddr == 0) {
printf("\r\nError! Can't allocate memory!\r\n");
while (1) {}
}
cam_config.output_bufsize = CAM_OUTPUT_BUFFER_SIZE;
bflb_cam_init(cam0, &cam_config);
#if defined(BL618DG)
bflb_cam_int_mask(cam0, CAM_INTMASK_NORMAL, false);
#endif
bflb_cam_start(cam0);
for (i = 0; i < CAM_FRAME_COUNT_USE; i++) {
while (bflb_cam_get_frame_count(cam0) == 0) {}
pic_size = bflb_cam_get_frame_info(cam0, &pic);
#if defined(BL618DG)
bflb_cam_int_clear(cam0, CAM_INTCLR_NORMAL);
#else
bflb_cam_pop_one_frame(cam0);
#endif
printf("pop picture %d: 0x%08x, len: %d\r\n", i, (uint32_t)pic, pic_size);
}
bflb_cam_stop(cam0);
//for (i = 0; i < pic_size; i++) {
// printf("%02x", pic[i]);
//}
//printf("\r\n");
printf("end\r\n");
while (1) {
bflb_mtimer_delay_ms(1000);
}
}FAQ
Can't identify sensor
The camera I2C address or wiring is wrong: confirm the sensor is in the image_sensor component list, and that SDA/SCL are connected with shared ground and power.
Frame count does not increase
Confirm the DVP data/clock/hsync/vsync lines are correct and the sensor is outputting; confirm the output buffer allocated (memalign) and large enough for 416×240×2×2.
I want another resolution
Change CROP_WQVGA_X/Y and the crop ranges, and adjust CAM_OUTPUT_BUFFER_SIZE accordingly.
Have questions?
For any other questions, visit the unified Q&A and discussion board: Ai-Thinker Discussions