Updated GPIO pins and description in README

README.md

@@ -1,6 +1,6 @@
 # Selfiebooth Baas van Horst aan de Maas
 
-![Illustration Selfiebooth](illustration.png)
+![Illustration Selfiebooth](doc/illustration.png)
 Python code and assets Selfiebooth Baas van Horst aan de Maas.
 
 ## Hardware setup
@@ -9,9 +9,23 @@ Python code and assets Selfiebooth Baas van Horst aan de Maas.
 
 Connect raspberry PI camera module to board
 
+![Camera connection](doc/camera_connection.png)
+
 ### 2. GPIO setup for button
 
-TODO: Add readme for GPIO setup (hardware)
+We use BCM pin 3 (index 5) since it has an internal pull-up resistor. This means that the digital value will get pulled-up 
+to 1 if it is floating (no connection to the ground or a 3v or 5v output). Pin 3 is floating when our switch is open, so since 
+we have a pull-up resistor, the digital value will be 1 when the swich (push button) is open (not pressed). If the push button
+is pressed, we would like the value to go from 1 to 0 and raise a falling event. Therefore, the other wire needs to be 
+attached to the ground (index 9). We use a pull-up vs a pull-down since it is less sensitive for interference.  
+
+Index 3 (BCM pin 3) and index 9 (ground) are illustrated in this figure:
+
+![GPIO set-up](doc/gpio_setup.png)
+
+Here you see a photo of the connection:
+
+![GPIO connection](doc/gpio_connection.png)
 
 ## Software setup
 

src/selfiebooth.py

@@ -11,6 +11,8 @@
 import picamera
 import RPi.GPIO as GPIO
 
+BCM_PIN = 3
+
 
 class Selfiebooth(picamera.PiCamera):
 
@@ -54,8 +56,8 @@ def __init__(self, config, raw_output_dir):
     @staticmethod
     def _setup_gpio():
         GPIO.setmode(GPIO.BCM)
-        GPIO.setup(17, GPIO.IN, GPIO.PUD_UP)
-        GPIO.add_event_detect(17, GPIO.FALLING)
+        GPIO.setup(BCM_PIN, GPIO.IN)
+        GPIO.add_event_detect(BCM_PIN, GPIO.FALLING)
 
     def _setup_overlays(self):
         self._flash_overlay.alpha = 0

test/gpio.py

@@ -1,17 +1,16 @@
 #!/usr/bin/env python
 
-import os.path
-import sys
 from time import sleep
-
-# GPIO
 import RPi.GPIO as GPIO
+
+BCM_PIN = 3
+
 GPIO.setmode(GPIO.BCM)
-GPIO.setup(17, GPIO.IN, GPIO.PUD_UP)
-GPIO.add_event_detect(17, GPIO.FALLING)
+GPIO.setup(BCM_PIN, GPIO.IN)
+GPIO.add_event_detect(BCM_PIN, GPIO.FALLING)
 
 while True:
     sleep(.01)
-    if GPIO.event_detected(17):
+    if GPIO.event_detected(BCM_PIN):
         print "pressed"