GPIO Zero - eclubiitk/EClub-Handbook GitHub Wiki

GPIO Zero is a Python API used to programme the RPi . It is easy to use and very friendly for beginners to start with . It's code is simpler to read & as short as possible .
The GPIO Zero library takes the class method approach to control, as opposed to the function method approach of RPi.GPIO and other, similar libraries . Pins become Python objects, which must be set up before use.

There are various inbuilt function in GPIOZero(library) like LED, Button, PWMLED etc.. we can use these functions in either of the following format:

1. first is to import explicitly so that function can be directly used in script. for example:

• from gpiozero import Button and Button can be used directly. or

2. import whole GPIO Zero library.But here all references to items within GPIO Zero must be prefixed:

• led = gpiozero.LED()

WiringPi pin number/BCM GPIO

PIN numbering can be done in various ways. some of them are as follows:

1. If you wish to use physical (BOARD) numbering you can specify the pin number as “BOARD(number)”
2. Wiring pi pin numbers : we can use WPI(wpinumber)
3. you can specify pin as header:number (here header for raspberry pi B+ is J8 and number is physical pin)

Note: the numbering of the GPIO pins is not in numerical order; GPIO pins 0 and 1 are present on the board (physical pins 27 and 28) but are reserved for advanced use (see below).Any pin marked “GPIO” in the diagram below can be used as a pin number. For example, if an LED was attached to “GPIO17” you would specify the pin number as 17 rather than 11

1. 5V pin : pin(BOARD) 2 & 4
2. 3V3 pin : pin(BOARD) 1 & 17
3. GROUND pin : pin(BOARD) 6 ,9, 14, 20, 25, 30, 34, 39

A GPIO pin designated as an output pin can be set to high (3V3) or low (0V).

It is a tiny library to make reading buttons very simple.

gpiozero.Button(pin) or Button(pin)

Here are some functions related to Button:
Let button = Button(pin)

• button.when_pressed
  It runs the function when the device changes state from inactive to active
• button.when_released
  It runs the function when the device changes state from active to inactive
• button.when_held
  It runs the function when device remains active.
• button.value
  If button is currently pressed return 1
  otherwise 0
• button.is_pressed
  If button is currently pressed return True
  otherwise False
  (unlike value it's always a boolean)
• button.hold_time
  The length of time(seconds) to wait after the device is activated
• button.hold_repeat
  If True when_held will be executed repeatedly.
• button.held_time
  The length of time device has been held for
• wait_for_press(timeout=value) (None is default value)
  Pause the script until the device is activated, or the timeout is reached.
• wait_for_release(timeout=value) (None is default value)
  Pause the script until the device is deactivated, or the timeout is reached.

Here is a code to understand better:

'''this is a simple code for blinking of led with the help of  gpiozero library'''

from gpiozero import Button   #this imports the Button class from the gpio lirary. 

button = Button(2)      # 'button' is variable name can be anything and this becomes the object.

while True:
    if button.is_pressed:       # this calls the is_pressed() function 
         print("button is pressed")
    else:
         print("button is not pressed")
    

This library uses BCM method of numbering as default. So there is no need to tell which to use. Also any output pin is called LED .This is because it is defined as LED class .

gpiozero.LED(pin)  or  LED(pin)

Here are some function for LED:
let led = LED(pin)

• led.blink(on_time = 1, off_time = 1,n=None) (values given are default)
  • it's parameter are:
    • on_time(float) : number of seconds on
    • off_time(float) : number of seconds off
• led.off() turn the device off.
• led.on()
  turn the device on.
• led.toogle()
  Reverse the state of the device. If it’s on, turn it off; if it’s off, turn it on.
• led.islit
  if active returns True
  otherwise False
• led.pin
  The pin through which device is connected.
• led.value
  if active returns 1
  otherwise 0

Here is a code to understand better:

'''this is a simple code for blinking of led with the help of  gpiozero library'''

from gpiozero import LED   #this imports the LED class from the gpio lirary.
from time import sleep 

led = LED(18)       # 'led' is variable name can be anything and this becomes the object.

while True:
    led.on()       # this calls the on() function of LED class for object led.
    sleep(1)
    led.off()      # this calls the off() function.
    sleep(1) 
    

As known PWM is technique for getting analog results from digital means . So this class can be used for variable output .

gpiozero.PWMLED(pin)  or PWMLED(pin)

Here are some functions :
let led = PWMLED(pin)

• (on,off,pin,is_lit) works same as LED function.

• led.blink(on_time=1, off_time=1, fade_in_time=0, fade_out_time=0, n=None) (values given are default)

  • It's parameter:
    • on_time, off_time, n are same as in LED
    • fade_in_time (float) – Number of seconds to spend fading in. Defaults to 0.
    • fade_out_time (float) – Number of seconds to spend fading out. Defaults to 0.

• led.value = val
  Through this brightness of the led can be set . It should be noted the value must lie between '0' & '1' .

• led.pulse(fade_in_time=1, fade_out_time=1, n=None)
  This is similar to blinking with brightness fading in and out .

Here is a code to understand better:

'''this is a simple code for blinking of led with the help of  gpiozero library'''

from gpiozero import PWMLED   #this imports the PWMLED class from the gpio lirary.
from time import sleep 

led = PWMLED(18)       

while True:
    led.value = 0        # off
    sleep(1) 
    led.value = 0.5      # half brightness
    sleep(1)
    led.value = 1        # full brightness
    sleep(1)
    

It represent full color LED component(composed of red,green and blue LED)

gpiozero.RGBLED(red,green,blue)  or  RGBLED(red,green,blue)

• Parameters:
  • red(int) : The GPIO pin that control the red component of RGB LED.
  • green(int) : The GPIO pin that controls the green component of the RGB LED.
  • blue (int) – The GPIO pin that controls the blue component of the RGB LED.

Here are some Functions related to RGBLED:
LET led = RGBLED(pin)

• on, off, toggle, is_lit, blink works same as PWMLED.
• led.color
  Represent the color of LED as a tuple of(red,green,blue).

In this Function you will learn how to use a buzzer (or piezo speaker) with Raspberry Pi. Buzzers can be found in alarm devices, computers, timers and confirmation of user input such as a mouse click or keystroke.

gpiozero.Buzzer(pin)  or  Buzzer(pin)

Some function related to Buzzer are:
Let bz = Buzzer(pin)

• (off, on, toggle, pin) works same as in LED or PWMLED.
• bz.beep(on_time=1,off_time=1,n=None) (values given are default values)
  on_time(float) : Number of seconds on.
  off_time(float) : Number of seconds off.
  n(int) : Number of times to blink.