Differences

This shows you the differences between two versions of the page.

--- gpio_inputs_-_button_led_control [2016/08/09 20:47] – walkeradmin
+++ gpio_inputs_-_button_led_control [2017/10/22 16:38] – [The Button in Action] walkeradmin
@@ Line 20: / Line 20: @@
 {{:pulluppulldown.png?400|}}
 \\
+\\
+So for any input that we are waiting for a high signal (3.3v) we will use pull down so it stays a 0v, for any pin we are waiting for a low signal (0v) we will use a pull up so it stays at 3.3v (until a button press makes it low)
 \\
 \\
@@ Line 29: / Line 31: @@
 \\
     sudo nano LED-Button.py
+\\
+** You can download the code {{ :led-button.zip |Here}}: **
 \\
     #import modules
     import RPi.GPIO as GPIO    # This imports the GPIO libarary that allows the use of the GPIO pins,
-    import time                # This imports the time libarary (for delays among other things)
                                # These libraries are built in to Raspbian.
     GPIO.setmode (GPIO.BOARD)  # This sets the GPIO pin numbering. Our LED is connected to Pin 12,
@@ Line 41: / Line 43: @@
                                # 12 is called GPIO18 (a reference to its place on the chip).
-    GPIO.setup(12, GPIO.OUT)   # Sets the GPIO pin as output. (as opposed to input, which would
+    GPIO.setup(11, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) # setup GPIO Pin 11 as an input, and set
-                               # read in a voltage (but only in terms of a 0 or a 1))
+                                                        # the resistor to Pull Down (PUD_DOWN)
+                                                        # this is the pin the button is connected to
+                                                        # button is connected from pin 11 to the
+                                                        # +3.3v pin on the GPIO
+    GPIO.setup(12, GPIO.OUT)   # Sets the GPIO pin as output. This is connected to the LED, then
+                               # from the LED to 0v via a 330 Ohm resistor.
     GPIO.output(12, 0)         # sets the GPIO Pin 12 to low (so 0v)
-    time.sleep(1)              # waits one second (settling time)
+    try:
+            while True:                             # start a loop
+                    if (GPIO.input(11) == 0):       # if GPIO pin 11 is a 0 (Low (0v)) then..
+                            GPIO.output(12,0)       # set Pin 12 to 0v (LED Stays off)
+                    else:                           # if GPIO pin is anything other than High (3.3v) then..
+                            GPIO.output(12,1)       # set Pin 12 to 3.3v (LED comes on)
+    except KeyboardInterrupt:                       # if Ctrl-C is pressed, exit loop
+            GPIO.cleanup()                          # reset GPIO pins to default state
-    GPIO.output(12, 1)         # sets the GPIO Pin 12 to high (so 3.3v) LED will turn on
+    #End
+\\
-    time.sleep(3)              # waits 3 seconds, so LED will be on for 3 seconds
+\\
+==== The Button in Action ====
-    GPIO.cleanup()             # Resets all the GPIO pins to their default state (LED will go off)
+Here is the button turning on the LED {{:led-button.mp4|950x574|autoplay,loop}}
+\\
+\\
+==== A Small Issue ====
+\\
+While this code works without any real problems, because we are in a constant loop, this code is very heavy on CPU load, on the Pi Zero I am using this causes the processer to sit at 100 %, a better method is to use an **interrupt**
+\\
+\\
+This guide is comprised of information from a youtube video by **Gaven MacDonald**. Thanks Gaven.
+\\
+\\