@kidswong999
我确实觉得你的实现是简单有效的，我思考了一下，用状态机转换的思想其实还是可以完全替代定时器+外部中断的，确实我发现一个很致命的地方，OpenMV管脚连上杜邦线以后，只要杜邦线有物理上的抖动，很容易引起OpenMV管脚上接收到电平的变化。

@lemron
软件I2C或者SPI吧应该是，只能通过协议在总线上进行数据交换，不然就通过串口直接发送。

问题描述：
完成程序提供如下，程序目的是在接收到外部中断以后先读取文件，然后依据读取到文件中的序号创建名如video_1.mjpeg的mjpeg对象，当我将外部中断中的“File operation部分放到程序初始化的部分即‘/Creation of mjpeg object & read file operation’”时，程序运行没有问题；当然地，我需要在不断电的情况下录制多个视频，我就应该将这段代码放置到外部中断的callbackfunction中，但这样一来运行时就会弹出错误：
line = 13
No. 1
Uncaught exception in ExtInt interrupt handler line 13
MemoryError:

请问应该如何解决这个/类错误呢？

代码：

import sensor, image, time, pyb, mjpeg


# -----</Definition of variables>-----

sleep_flag = 1
index_i = 0
time_1s = 0

TIME_ONEMIN_INSEC = 60
TIME_FIVEMIN_INSEC = TIME_ONEMIN_INSEC * 5
TIMER_THREE_WORKING_FLAG = 0
RED_LED_PIN = 1
GREEN_LED_PIN = 2
BLUE_LED_PIN = 3

# <Definition of variables/>------------------------------------------------------------


sensor.reset()                      # 重置并初始化传感器。
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA)   # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000)     # Capture frames for 2000ms.
pyb.LED(RED_LED_PIN).on()
time.sleep(1000)
pyb.LED(RED_LED_PIN).off()
sensor.sleep(True)                  # 启用传感器睡眠模式（节省约40mA)



# -----</Definition of Clock object>-----

clock = time.clock()

# </Definition of Clock object>---------------------------------------------------------


# -----</Creation of mjpeg object & read file operation>-----

f = open('/number.txt', 'r')
context = f.read()
index = int(context)
print("Current index is", index)
f.close()
m = None

# <Creation of mjpeg object & read file operation/>-----------------------------------------------------------


# -----</Timer>-----

# Timer_3 callback function
def tick_3(timer):
    global time_1s
    global TIMER_THREE_WORKING_FLAG
    time_1s = time_1s + 1
    print('time_1s =', time_1s)
    if time_1s >= 10:
        time_1s = 0
        sensor.sleep(True)
        TIMER_THREE_WORKING_FLAG = 0
        print("TIMER_THREE_WORKING_FLAG =", TIMER_THREE_WORKING_FLAG)
        timer.deinit()

# Configuration of timer_3
tim_3 = pyb.Timer(3, freq = 1)
tim_3.deinit()

# Timer_4 callback function
def tick_4(timer):
    global time_1s
    global sleep_flag
    global TIMER_THREE_WORKING_FLAG
    time_1s = time_1s + 1
    print('time_1s =', time_1s)
    if time_1s >= TIME_FIVEMIN_INSEC:
        time_1s = 0
        TIMER_THREE_WORKING_FLAG = 1        #If possible, stop and save the recording firstly
        sleep_flag = 1
        print("sleep_flag =", sleep_flag)
        tim_3.init(freq = 1)
        tim_3.callback(tick_3)
        print("Timer_3 has been activated!")
        print("TIMER_THREE_WORKING_FLAG =", TIMER_THREE_WORKING_FLAG)
        #m.close(clock.fps())      #Uncomment it later
        timer.deinit()

# Configuration of timer_4
tim_4 = pyb.Timer(4, freq = 1)
tim_4.deinit()



#tim_4.callback(tick_4)

# <Timer/>------------------------------------------------------------------------------


# -----</External interrupt>-----

def ext_callback(line):
    global index_i
    global index
    global sleep_flag
    global time_1s
    global tim_4
    global tim_3
    global TIMER_THREE_WORKING_FLAG
    global m

    print("line =", line)
    index_i = index_i + 1;
    print("No.", index_i)

    # Use the idea of state machine to think about these codes, there are only three states within this machine
    if sleep_flag == 1 and TIMER_THREE_WORKING_FLAG == 0:       # Sensor is sleeping and Timer_3 is not working
        sensor.sleep(False)
        time_1s = 0

        # File operation
        f = open('/number.txt', 'r')
        context = f.read()
        index = int(context)
        print("Current index is", index)
        index = index + 1
        f.close()
        f = open('/number.txt', 'w')
        print("%d is gonna to be written into the file" %index)
        f.write("%d" %index)
        f.close()
        m = mjpeg.Mjpeg("video_%d.mjpeg" %index)

        tim_4.init(freq = 1)    # To design a stoppable recording, I need to design carefully here
        tim_4.callback(tick_4)
        print("Timer_4 has been activated!")
        sleep_flag = 0
    elif TIMER_THREE_WORKING_FLAG == 1:     #sleep_flag == 0 or TIMER_THREE_WORKING_FLAG == 1
        pass
    else:       # Timer_4 is still working
        time_1s = 0
        sleep_flag = 1
        print("sleep_flag =", sleep_flag)
        tim_3.init(freq = 1)
        tim_3.callback(tick_3)
        TIMER_THREE_WORKING_FLAG = 1
        print("Timer_3 has been activated!")
        print("TIMER_THREE_WORKING_FLAG =", TIMER_THREE_WORKING_FLAG)
        #m.close(clock.fps())      #We should put this one in the while loop
        tim_4.deinit()

# Falling edge triger
extint = pyb.ExtInt(pyb.Pin('P8'), pyb.ExtInt.IRQ_FALLING, pyb.Pin.PULL_UP, ext_callback)

# <External interrupt/>-----------------------------------------------------------------


# Recording up to 5min, then sleep again

while (True):
    if sleep_flag == 0:
        for i in range(200):        # This vedio lasts exactly ten seconds
            clock.tick()
            m.add_frame(sensor.snapshot())
            #print(clock.fps())
        if TIMER_THREE_WORKING_FLAG == 1:       # Which means we should store the video now
            m.close(clock.fps())
            print("Bye~See u next time")
            print("Owned by Donkey_F, all rights reserved")

啊，确实是好方法，谢谢！
不过我最终想要实现的其实是接收到外部中断以后，通过翻转一个flag的值，然后在while循环里面进行一次录像操作（依据官方的例程，for i in 200那个循环，其实就是录像10s），所以想while里面到时候就放这一块录10s的代码，然后不断循环。
但仔细想一想，其实你提供的程序里面通过utime.tick_diff也实现了这种操作。我设计初衷其实是想留出一个灵活的方法给上层调用的——第一次下降沿开始录像，如无意外录5min；但调用者也可以通过产生第二个下降沿的方法中断录像。

问题描述：
我现在想要编写一段程序，实现以下功能：程序初始化以后关闭感光元件，等待外部中断的到来，外部中断接收到以后启动定时器，12秒以后关闭定时器，并且再次关闭感光元件，而while循环主要就是通过一个变量判断是否进行采图工作。现在程序能实现接收外部中断，并启动定时器，而且能够在12秒以后在terminal中打印出sleep_flag = 1的语句（证明定时器能够正常工作），但打印完以后马上跳出来一个错误：

Traceback (most recent call last):
File "", line 96, in
RuntimeError: Sensor Timeout!!

请教一下各位，这是什么原因引起的呢？应该如何解决呢？谢谢！

程序源码：

import sensor, image, time, pyb


# -----</Definition of variables>-----

sleep_flag = 1
index_i = 0
time_1s = 0

TIME_ONEMIN_INSEC = 12
RED_LED_PIN = 1
GREEN_LED_PIN = 2
BLUE_LED_PIN = 3

# <Definition of variables/>------------------------------------------------------------


sensor.reset()                      # 重置并初始化传感器。
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA)   # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000)     # Capture frames for 2000ms.
pyb.LED(RED_LED_PIN).on()
time.sleep(1000)
pyb.LED(RED_LED_PIN).off()
sensor.sleep(True)                  # 启用传感器睡眠模式（节省约40mA)



# -----</Definition of Clock object>-----

clock = time.clock()

# </Definition of Clock object>---------------------------------------------------------


# -----</Creation of mjpeg object>-----

#???

# <Creation of mjpeg object/>-----------------------------------------------------------


# -----</Timer>-----
def tick_4(timer):
    global time_1s
    global sleep_flag
    time_1s = time_1s + 1
    print('time_1s =', time_1s)
    if time_1s >= TIME_ONEMIN_INSEC:
        time_1s = 0
        sleep_flag = 1
        print("sleep_flag =", sleep_flag)
        sensor.sleep(True)
        timer.deinit()

# defination of timer_4
tim_4 = pyb.Timer(4, freq = 1)
tim_4.deinit()
#tim_4.callback(tick_4)
# <Timer/>------------------------------------------------------------------------------


# -----</External interrupt>-----

def ext_callback(line):
    global index_i
    global sleep_flag
    global time_1s
    global tim_4
    print("line =", line)
    index_i = index_i + 1;
    print("No.", index_i)
    sensor.reset()                      # 重置并初始化传感器。
    sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
    sensor.set_framesize(sensor.QVGA)   # Set frame size to QVGA (320x240)
    sensor.skip_frames(time = 2000)     # Capture frames for 2000ms.
    time_1s = 0
    tim_4.init(freq = 1)
    tim_4.callback(tick_4)
    print("Timer_4 has been activated!")
    if sleep_flag == 1:
        sleep_flag = 0
    #else:
       # sleep_flag = 1

# Falling edge triger
extint = pyb.ExtInt(pyb.Pin('P8'), pyb.ExtInt.IRQ_FALLING, pyb.Pin.PULL_UP, ext_callback)

# <External interrupt/>-----------------------------------------------------------------


# Recording up to 5min, then sleep again

while (True):
    if sleep_flag == 0:
        sensor.snapshot()

就是dfu升级不需要USB连接成功对吗

问题描述：
我不小心将未经测试的休眠函数pyb.stop()写到了程序的基本上是最前面了……然后自然而然地，OpenMV上电以后自动运行此函数，导致电脑无法检测到M7的USB连接，请问要怎么做才能擦除/重初始化M7的main.py……谢谢！

啊！如你所说，我认为应该是STM32IO控制有问题，M7接下拉以后接到STM32的Vcc管脚，能检测到电平变化，确实用万用表再仔细测量发现，IO输出无电平变化，现在在查找原因，后续我会说明解决方法的，谢谢你

是这样子的，STM32开发板上我设置为按一下按键，该IO口的电平翻转，并且LED灯状态翻转，用万用表测试过，确实电平会改变。

问题描述：
我的OpenMV M7现在遇到了一个问题——用杜邦线将其中一个IO口与STM32开发板某一个IO口进行连接以后（杜邦线连接稳定，无松动）改变STM32开发板该端口的输出电平，M7无法正常读取其电平值，但当我按下STM32开发板的复位键时，M7能检测到该管脚那一瞬间的电平变化，这又是为什么呢？

细节：
STM32该端口采用推挽输出，M7的Pin配置为输入模式，接下拉电阻

M7的测试代码：

import sensor, pyb, time

pin7_in = pyb.Pin('P8', pyb.Pin.IN, pyb.Pin.PULL_DOWN)

while (True):
    time.sleep(100)
    print(pin7_in.value())