【Chuanglong TL570x-EVM】Button control LED light

lugl4313820

【Chuanglong TL570x-EVM】Button control LED light [Copy link]

[Preface] The example gives Python programs to control LED flashing and detect key presses, combining two case studies to synthesize a key control example.

[Analysis] The LED flashing light is maintained by a loop to detect whether to exit. I add a thread here to start it. The button program is detected by even. If another thread is added, the program will not be able to exit.

[Implementation ideas] Press the key test to determine whether the key is pressed, and then update the delay seconds to control the flashing speed of the LED light.

1. Initialize LED:

 def __init__(self):
        self.led_path = "/sys/class/leds/"    # Led path
        self.leds     = []          # Save the led found
        self.enumerate_led()
        self.led_time = 0.1
        self.key_sta = 1

    """ enumerate all led """
    def enumerate_led(self):
        led_name = "user-led"

        """ find led """
        for filename in os.listdir(self.led_path):
            if led_name in filename:
                self.leds.append(os.path.join(self.led_path, filename))

        if len(self.leds) == 0:
            return False

        """ 
        led sort, e.g.
        /sys/class/leds/user-led0
        /sys/class/leds/user-led1
        /sys/class/leds/user-led2
        """
        self.leds.sort()

        print "find leds:"
        for led in self.leds:
            print led

        return True

2. LED flashing program:

""" control led flash """
    def flash_led(self):
        led_num = len(self.leds)

        while not KeyDevice.quit_flag:
            """ Turn on leds """
            for i in range(led_num):
                """ Set the led brightness value to 1 to turn on the led """
                ret = os.system("echo 1 > %s/brightness" % (self.leds))
                
                if ret != 0:
                    print "Error: Failed to turn on %s" % self.leds

            """ Keep the leds on for 500 ms """
            time.sleep(self.led_time*self.key_sta)

            for i in range(led_num):
                """ Set the led brightness value to 0 to turn off the LED """
                os.system("echo 0 > %s/brightness" % (self.leds))

            """ Keep the leds off for 500 ms """
            time.sleep(self.led_time*self.key_sta)

3. Key detection procedure:

def open_device(self, key_dev):
        try:
            """ open key device, if success, return True"""
            self.key_dev = evdev.InputDevice(key_dev)
            return True
        except Exception as e:
            print e
            return False
            
    def listen_key_pressed(self):
        try:
            print "Please press the key to test.\n"

            """
            Listen for the button to be pressed
            event.value: 1: pressed; 0: released
            """
            for event in self.key_dev.read_loop():
                if event.type == evdev.ecodes.EV_KEY:
                    if event.code == evdev.ecodes.KEY_PROG1 and event.value == 1:
                        print "User key0 pressed!\n"
                        self.key_sta = 1

                    elif event.code == evdev.ecodes.KEY_PROG2 and event.value == 1:
                        print "User key1 pressed!\n"
                        self.key_sta = self.key_sta + 1
                        if self.key_sta >20:
                            self.key_sta = 1
                        

        except Exception as e:
            if not KeyDevice.quit_flag:
                print e

4. CTRL+C to exit the program:

 @classmethod
    def stop(cls):
        print "ctrl + c ..."
        cls.quit_flag = True
        sys.exit()

5. CTRL+C signal:

def sig_handle(signum, frame):
    print "ctrl + c ..."
    KeyDevice.stop()
    sys.exit()

6. Startup:

if __name__ == '__main__':

key_dev = "/dev/input/event0" # key deivce path

try:

""" Ctrl+c handler """

signal.signal(signal.SIGINT, sig_handle)

key_device = KeyDevice()

""" open key device """

res = key_device.open_device(key_dev)

if not res:

print "open %s failed!" % key_dev

exit(3)

t1 = threading.Thread(target=key_device.flash_led)

t1.start()

""" Listen for the button to be pressed """

key_device.listen_key_pressed()

except Exception, exc:

print exc

[Experimental phenomenon] After the program is started, the three lights flash quickly. Press button 4 and the lights flash slower. When it is as slow as once every 2 seconds, press it again and the lights return to the original flashing frequency.

This experiment mainly learned python to detect GPIO input and output control.

[Summary] Python programming is relatively easy, but unfortunately events are only supported in Python 2.7. I'm used to Python 3, so it's a bit strange to go back to Python 2. Python pip doesn't support package installation, so I can't use it to my advantage. I hope the official will release a tutorial on how to add packages.

hahhk

Learned

hahhk

What commands can be used to control the LED

lugl4313820

hahhk posted on 2022-5-25 10:31 What command can be used to control the LED

Several commands are available, including .sh file operations, C, Python, and many other commands.

lele_liu

Thanks for sharing, thank you................