Pi GPIO pins Control

Controlling Input and Output Pins:

The Raspberry Pi2 is designed with a 40-pin connector that can be controlled by software.

The 40-pin header is made-up of many general purpose input and output(GPIO) pins.

Below is the complete pin diagram of Raspberry Pi2 GPIO Header.

 Lessons learnt form chapter:

·       Electronic circuits: Closed circuit, Open circuit, Short Circuit.

·       Current in a circuit, Voltage around the circuit, Resistance of the circuit.

·       Light emitting diode (LED)

·       Breadboard and its layout, connection of raspberry pi to breadboard.

·       GPIO Header:  pin numbers and their configuration.

·       GPIO pin as basic output.

·       GPIO pin as basic input.

·       Pull-up and Pull-down resistors.

 My Experiments:

1.       Using Pi as power supply to LED:

Things Needed:

·       R-Pi

·       40 pin GPIO Ribbon Cable with T-Shaped Breakout Board/ female to male wires

·       Power Supply

·       LED

·       Resistor (330 ohms)

·       Jumper wires

Process:

               First connected the GPIO header to T-Shaped Breakout Board using the 40 pin female to female GPIO Ribbon Cable. Next inserted the T-Shaped Breakout Board on the breadboard with the pins on either side of the center division on the breadboard. Instead of female to female to GPIO Ribbon Cable with T-Shaped Breakout Board, can also use female to male wires directly. Connected a wire from pin1 of the GPIO header with 3.3 V to anode (+ve terminal) of the LED. Other end of LED is connected to resistor. The other end of the resistor is connected to GND (any GND pin of GPIO header). The circuit connection is completed.

Switched on Power supply to Pi, LED turned ON.

2.       Controlling GPIO2 Pin as Basic Output:

Things Needed:

·       R-Pi

·       40 pin GPIO Ribbon Cable with T-Shaped Breakout Board/ female to male wires

·       Power Supply

·       LED

·       Resistor (330 ohms)

·       Jumper wires

Process:

                The pin3 or the GPIO2 pin of Pi can be used as the Input/Output.

The functionality of the pin is controlled by python program. Before that in order to test the functionality first modified the above circuit by simply connected the anode of LED to the GPIO2 pin instead of the 3.3V pin. Then switched on the power supply and executed the below python program from terminal. The LED is now blinking.

Program:

import RPi.GPIO

import time

RPi.GPIO.setmode(RPi.GPIO.BCM)

RPi.GPIO.setup(2,RPi.GPIO.OUT)

while True:

                RPi.GPIO.output(2, True) # RPi.GPIO.output(2, RPi.GPIO.HIGH)

                time.sleep(1)

                RPi.GPIO.output(2, False) #RPi.GPIO.output(2, RPi.GPIO.LOW)

                time.sleep(1)

Wrote the program, to make the LED glow for 1 second then stop. This is because, alternatively made the GPIO2 pin high and low. 

Done varies experiments by different series and parallel connection and also used different I/O pins for the experiments.

Experiment Results:

The I/O pins of Pi can be used as basic output source.

With different Combinations of the input like serial and parallel connection LED brightness varied due to different voltages in different connection.

In parallel connection all the LED glow with same brightness and vice versa in series due to varied voltages.

3.       Controlling GPIO2 Pin as Basic Input:

Things Needed:

·       R-Pi

·       40 pin GPIO Ribbon Cable with T-Shaped Breakout Board/ female to male wires

·       Power Supply

·       LED

·       Resistor (330 ohms)

·       Jumper wires

·       Momentary Push Button

Process:

               The pin3 or the GPIO2 pin of Pi can be used as the Input/Output.

The functionality of the pin is controlled by python program. Before that in order to test the functionality first need to construct the circuit as below. Connected the VCC point to pin1 for power supply and resistance from it and other end to GPIO2 pin. Then connected the Button between GPIO2 and GND.

Program:

import RPi.GPIO

import time

RPi.GPIO.setmode(RPi.GPIO.BCM)

RPi.GPIO.setup(2,RPi.GPIO.IN,pull_up_down=RPi.GPIO.PUD_UP)

while True:

  if RPi.GPIO.input(2) == RPi.GPIO.LOW:

              print("switch pressed.")

              break

RPi.GPIO.cleanup()

Wrote the program, to check the GPIO2 pin value. When switch pressed the GPIO2 pin gets low and release its high again. 

Experiment Results:

The I/O pins of Pi can be used as basic input source. Tested the experiment by using LED too.

In this case used the internal resistance of the pi too.