【创龙TL570x-EVM】按键控制LED灯

lugl4313820 发表于 2022-5-22 21:21

<div class='showpostmsg'> 本帖最后由 lugl4313820 于 2022-5-23 07:07 编辑

【前言】例程给了Python控制LED闪烁、检测按键的程序，结合两个案例学习综合一个按键控制例子。

【分析】LED闪灯，是循环检测是否退出的标志来维护的，我这里加入thread线程来开启。按键程序是even来检测的，如果再加入线程就会出现不能退出的现象。

【实现思路】按测键检来判断按键是否按下，然后更新延时秒数来控制LED灯闪烁的快慢。

1、初始化LED：

<pre>
<code> 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</code></pre>

2、LED闪烁程序：

<pre>
<code>""" 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)</code></pre>

3、按键检测程序：

<pre>

<code>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
</code></pre>

4、CTRL+C退出程序：

<pre>

<code> @classmethod
def stop(cls):
 print "ctrl + c ..."
 cls.quit_flag = True
 sys.exit()</code></pre>

5、CTRL+C信号：

<pre>

<code>def sig_handle(signum, frame):
print "ctrl + c ..."
KeyDevice.stop()
sys.exit()</code></pre>

6、启动：

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

【实验现象】程序启动后，三个灯快速闪烁，按下按键4，灯闪得慢下来，慢到2秒一次时，再按一下又回到原来的闪烁频率。

本次实验主要学习了python 检测GPIO的输入输出控制。

【总结】python编程还是相对容易的，但是遗憾的就是event只在python2.7中支持，现象已经用习惯了python3，突然回到python2还有点不习惯，python中pip也不支持安装包，所以发挥不出来。希望官方出个如何添加包的教程。

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hahhk 发表于 2022-5-25 10:24

学习了

hahhk 发表于 2022-5-25 10:31

用什么命令可以控制led

lugl4313820 发表于 2022-5-25 15:23

hahhk 发表于 2022-5-25 10:31
用什么命令可以控制led

好几种命令都可以，.sh操作文件，C也可以、Python也可以，N种

lele_liu 发表于 2022-6-5 09:42

感谢楼主的分享,谢谢................

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【创龙TL570x-EVM】按键控制LED灯