Nuts and Volts - May/June 2018

The first three lines should seem familiar to you (from the camera tutorial earlier). This program additionally includes importing modules that allow us to access and use the GPIO pins.

FIGURE 21. The cardboard camera stick. FIGURE 22. The pulley on the camera stick.

volts). Most of the remaining pins (such as GPIO02 or GPIO18) are ones you can use to output or read input in the form of electricity. The pins labeled “Ground” provide a return path for the electrical current. Numbering of the pins is done in the same fashion you read text in a book — left to right before moving down. You already have the code for capturing stills with the camera module. Let’s walk through how to set up the circuit and program.

The next few lines simply set up and define some of the components that the program will be using. buttonPin = 7,

count = 0, and buttonPress = True define variables; specifically, the number of the pin we are using to read input, how many stills you’ll take, and the state of the button (whether it’s being pressed or not).

GPIO.setmode( GPIO.BOARD) and GPIO.setup(buttonPin, GPIO.IN, pull_up_down =

Refer to Figure 19 and Figure 20 for the circuit. This is about as simple as it gets with the top wire connected to pin 6 and the bottom wire connected to pin 7.

GPIO.PUD_UP) prepare the pins for use. The most important part here is that pin 7 is being coded to read input. You’ve seen camera = PiCamera() before.

Here are the basics of the program that we will use. Note that the program allows you to take one still photograph which it saves to the Pi desktop (see Resources). Let’s walk through it quickly so that you have an intuitive understanding of its contents:

import RPi.GPIO as GPIO
from picamera import PiCamera
from time import sleep
 buttonPin = 7
 buttonPress = True
 count = 0
 GPIO.setmode(GPIO.BOARD)
 GPIO.setup(buttonPin, GPIO.IN, pull_up_down
 = GPIO.PUD_UP)
 camera = PiCamera()
while count < 1:
 buttonPress = GPIO.input(buttonPin)
 if buttonPress == False:
 
camera.capture(“/home/pi/Desktop/picture.jpg”
 count += 1