RPI Workshop for the Freie Universitat

Introduction

Cheap semiconductors and easy-to-use libraries allow everybody to improvise their own low-tech solutions for their daily problems. This tutorial gives a bit of insight on how to get started hacking with the Raspberry PI's GPIO.

For these examples you'll need python installed and a raspberry pi.

We'll implement a very simple button. What the button does is up to you. If you can make it print something on activation, you can also make it launch the zombie killing missiles ;)

Step 0: SSH to your RPI Zero W.

Requirements:

Windows: You might need to install an ssh client like Putty
Linux/OSX: Open a terminal.

Join the network

Join to the Telefonica NEXT Guest SSID with password "geenyguest".

Your rapberry pi zero should be pre-configured to connect to Telefonica NEXT Guest and it uses Bonjour to broadcast its hostname.

Once connected you can just type:

ssh pi@geeny1.local

Make sure to replace the number with your Raspberry Pi number.

Check that the Geeny Hub is running:

You can create a Geeny Dev account here

curl -H "Content-Type: application/json" -X POST -d '{"email":"<your-user>","password":"<your-password>"}' http://localhost:9000/api/v1/login

Step 1: Plugging everything together.

You will need only 2 cables and a switch button.

The input goes to the GPIO 23 (i.e second column. 8th row. Counting from top to bottom)
And the power (first column, first row)

Use this reference for details on the layout of the pinout

Step 2: GPIO Getting Started

Open your favorite editor and copy:

# We'll be using the GPIO library to
# interact with the hardware
import RPi.GPIO as GPIO

# There are different ways to "count" the pins.
# We'll use the Broadcom notation
GPIO.setmode(GPIO.BCM)

# It's a Button. Then is an IN-put. We can select if we want to activate it
# as pull-down (activated on pressed) or pull-up. (Activated on release)
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

try:
  while True:
      # 23 is the pin number based on BCM we wanted.
      if GPIO.input(23):
          print("Button 1 pressed")

# Takes care of cleaning up after is done
except KeyboardInterrupt:
  pass
finally:
  print "Exit: Cleanup"
  GPIO.cleanup()

Test your code in the Raspberry Pi

# Copy the file
$ scp button.py pi@raspberrypi.local:~/
# Run the code:
$ ssh pi@raspberrypi.local
$ python button.py

Press the button. What's the behaviour? Anything wrong?

Step 3: Fixing Debouncing

There are multiple points on which the conditions are met. Especially shortly after the switch button presses against the contact points.

Bouncing

The topic of switch bouncing is super interesting!

One way to deal with it is to use a sleep/wait function.

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

try:
  while True:
    if GPIO.input(23):
        print("Button pressed")
        while True:
            if not GPIO.input(23):
                print("Button released")
		break
    time.sleep(0.1)

except KeyboardInterrupt:
  pass
finally:
  print "Exit: Cleanup"
  GPIO.cleanup()

Step 4. Make it do something cool!

From twilio's documentation:

A common solution we have seen is SMS powered emergency button for the care of the elderly.

import RPi.GPIO as GPIO
import time
import os

from twilio.rest import Client

# Your Account SID from twilio.com/console
account_sid = "<Account ID>"
# Your Auth Token from twilio.com/console
auth_token  = os.environ["TWILIO_SECRET"]

client = Client(account_sid, auth_token)

def send_alert():
  message = client.messages.create(
    to="<a registered number>",
    from_="+18312221512",
    body="Diego! RED ALERT!")
  print("Sent: ", message.sid)

GPIO.setmode(GPIO.BCM)
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

try:
  while True:
    if GPIO.input(23):
      while GPIO.input(23):
        pass
      send_alert()
	time.sleep(0.1)

except KeyboardInterrupt:
  pass
finally:
  print "Exit: Cleanup"
  GPIO.cleanup()

Step 5. Make it Geeny Enabled!

We'll need to create a device with a serial number using the following snippet:

curl -X POST \
    -H 'Content-Type: application/json' \
    -H 'Accept: application/json' \
    -d '{
        "name": "<name-of-your-thing>",
        "serial_number": "123",
        "thing_type": "877827cc-0c78-4e55-80fe-2941479c681a"
        }' \
    'http://localhost:9000/api/v1/things' > thing.info

And now we can use our geeny-hub image to publish a message whenever the button is pressed.

import RPi.GPIO as GPIO
import time
import os
import requests
import json

# Fill these in.
EMAIL=""
PASSWORD=""
SERIAL_NUMBER=""

# Call the login function of the SDK. It requires a user-password.
def login():
  url = 'http://localhost:9000/api/v1/login'
  payload = json.dumps({'email': EMAIL, 'password': PASSWORD})
  headers = {'Content-Type': 'application/json'}
  response = requests.post(url, data=payload, headers=headers)
  return response.text == "success"

# A small wrapper around the publish endpoint of the SDK.
def publish():
  print("publishing message...")
  url = 'http://localhost:9000/api/v1/messages/' + SERIAL_NUMBER
  payload = json.dumps({'msgs': []})
  headers = {'Content-Type': 'application/json'}
  response = requests.post(url, data=payload, headers=headers)
  print(response.text)

def send_alert():
  publish()

def setup():
  if login():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
    print("GPIO setup done")
  else:
    raise "error in login"

def run():
  while True:
    if GPIO.input(23):
      while GPIO.input(23):
        pass
      send_alert()
    time.sleep(0.1)

try:
  setup()
  run()
except KeyboardInterrupt:
  pass
finally:
  print "Exit: Cleanup"
  GPIO.cleanup()

Mike4tech/fu-workshop