3.2. Flashing an LED

3.2.1. Our goal

In this tutorial, we are making a Grove Led flash continuously, while it’s being connected to a GoPiGo3 robot.

3.2.2. The code we analyse

The code we’re analyzing in this tutorial is the following one.

# import the EasyGoPiGo3 drivers
import time
import easygopigo3 as easy

# Create an instance of the GoPiGo3 class.
# GPG will be the GoPiGo3 object.
gpg = easy.EasyGoPiGo3()


# create the LED instance, passing the port and GPG
my_led = gpg.init_led("AD1")

# loop 100 times
for i in range(100):
    my_led.light_max() # turn LED at max power
    time.sleep(0.5)

    my_led.light_on(30)  # 30% power
    time.sleep(0.5)

    my_led.light_off() # turn LED off
    time.sleep(0.5)

The source code for this example program can be found here on github.

3.2.3. The modules

Start by importing 2 important modules:

import time
import easygopigo3 as easy

The easygopigo3 module is used for interacting with the GoPiGo3 robot, whilst the time module is generally used for delaying actions, commands, setting timers etc.

3.2.4. The objects

After this, we need to instantiate an easygopigo3.EasyGoPiGo3 object. We are using the EasyGoPiGo3 object for creating an instance of Led class, which is necessary for controlling the Grove Led device.

gpg = easy.EasyGoPiGo3()

Now that we have an EasyGoPiGo3 object, we can instantiate a Led object. The argument of the initializer method is the port to which we connect the Grove Led and it’s set to "AD1".

my_led = gpg.init_led("AD1")

Note

See the following graphical representation as a reference to where the ports are.

3.2.5. Main part

In this section of the tutorial we are focusing on 3 methods of the easysensors.Led class.

  • The light_max() method - which turns the LED at the maximum brightness.

  • The light_on() method - used for turning the LED at a certain percent of the maximum brightness.

  • The light_off() method - used for turning off the LED.

All in all, the following code snippet turns on the LED to the maximum brightness, then it sets the LED’s brightness at 30% and in the last it turns off the LED. The delay between all these 3 commands is set at half a second.

for i in range(100):
    my_led.light_max() # turn LED at max power
    time.sleep(0.5)

    my_led.light_on(30)  # 30% power
    time.sleep(0.5)

    my_led.light_off() # turn LED off
    time.sleep(0.5)

3.2.6. Running it

Connect the Grove Led to your GoPiGo3 robot to port "AD1" and then let’s crank up the Raspberry Pi. For running the analyzed example program, within a terminal on your Raspberry Pi, type the following 2 commands:

cd ~/Desktop/GoPiGo3/Software/Python/Examples
python easy_LED.py
http://i.imgur.com/OhqtJAO.gif