你这个rtc我看着不知道什么意思，如果要录制15小时, 可以用millis()判断.
import sensor, image, time, mjpeg, pyb
RED_LED_PIN = 1
BLUE_LED_PIN = 3
sensor.reset() # Initialize the camera sensor.
sensor.set_pixformat(sensor.RGB565) # or sensor.GRAYSCALE
sensor.set_framesize(sensor.QVGA) # or sensor.QQVGA (or others)
sensor.skip_frames(time = 2000) # Let new settings take affect.
clock = time.clock() # Tracks FPS.
pyb.LED(RED_LED_PIN).on()
sensor.skip_frames(time = 2000) # Give the user time to get ready.
pyb.LED(RED_LED_PIN).off()
pyb.LED(BLUE_LED_PIN).on()
m = mjpeg.Mjpeg("example.mjpeg")
print("You're on camera!")
start = pyb.millis()
while (pyb.millis()-start) < 15*60*60*1000:
clock.tick()
m.add_frame(sensor.snapshot())
print(clock.fps())
m.close(clock.fps())
pyb.LED(BLUE_LED_PIN).off()
print("Done! Reset the camera to see the saved recording.")