Raspberry Pi: An Advanced Guide to Setup, Expert Programming(Concepts, theories and techniques) and Build Raspberry Pi Projects by Grant Joe

Author:Grant, Joe [Grant, Joe]
Language: eng
Format: epub, pdf
Published: 2020-08-14T16:00:00+00:00

Understanding the Script

First of all, the states for enabling and disabling LEDs are required to be defined according to the RGB LED type that is being used (common cathode). If the RGB LED is an ‘Anode’, the states for enabling / disabling have to be reversed.

Then the mapping of GPIO with the pins according to the wiring done is to be defined.

By combining the basic colors red, blue, and green color combinations are also defined.

In this Python script, there are several noteworthy functions. Let us start with the led_setup(). This function forwards the numbering of the GPIO pins that are to be used as outputs to the GPIO.BOARD. Lastly, we also use the led_clear() function that reset the state of the pins, i.e., reverting the pins to their default setting with them being disabled.

On the Gpio header, the led_gpiocontrol() function assigns pre-defined states to either a single GPIO pin or, if required, all of the GPIO pins. The isinstance() function is used to determine whether a value matches a specific type, i.e., am integer. After this, the state of a single pin can be defined, or the user can go through the entire list of pins and define the state for each pin individually.

Subsequently, in order to control the lighting up of the LEDs, the appropriate functions are needed to be defined in the script. These functions are the led_activate() and led_deactivate() respectively. Moreover, to control the time span in which an LED stays switched on is defined by the led_time() . Note that this function is also used for keeping a specific color of the LED lit up in a cycle. When the time allotted by this function expires, the LED turns off and lights up with a new color on the next cycle.

Lastly, the led_cleanup() function is used to revert the state and value of the pins to default. Moreover, this function calls upon the GPIO.cleanup() function to release the GPIO pins from use.

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