Saturday, November 29, 2014

Big Ben Clock - Raspberry Pi

We mounted a large clock on the wall of our vaulted ceiling and wanted to give it a little more pizzazz. I wanted to give it a Big Ben feel, so I added some speakers, a Raspberry Pi, a little code, and voilĂ ! We now have a mini Big Ben of our own.

With a Wifi connector I am also able to remotely push other audio sounds to the speakers. Think speaker front end for a makeshift security system, or other audio states of your home automation. The possibilities are endless.



The following is the code I wrote for the cronjob schedule and bash script to determine which audio file to play.

cronjob schedule:
# hourly from 7am to 10pm
0 7-22 * * *  /opt/big_ben/ > /dev/null

# Author: Kenneth Burgener  2014
# Purpose: Determine hour and play appropriate Big Ben MP3

# crontab: (from 7am and 10pm)
# 0 7-22 * * *  /opt/big_ben/ > /dev/null

# Get hour (1-12) for mp3 file
HOUR=`date +%l`
HOUR=$(( $HOUR ))

# Get military hour (1-24) for math below
MILHOUR=`date +%k`

# Set audio volume depending on time of day
if [ $MILHOUR -le 8 -o $MILHOUR -ge 20 ] ; then
    # 8am and earlier, 8pm and later
    #/usr/bin/amixer set PCM 80% > /dev/null
    /usr/bin/amixer set PCM 90% > /dev/null
    # 9am to 7pm
    #/usr/bin/amixer set PCM 95% > /dev/null
    /usr/bin/amixer set PCM 91% > /dev/null

/usr/bin/mpg123 /opt/big_ben/audio/big_ben_$HOUR.mp3 2> /dev/null

Big Ben Audio

I found a good quality mp3 file that had the full 12 chimes. I then used Audacity to chop the file into smaller versions for the appropriate hour chimes.
    • big_ben_1.mp3
    • big_ben_2.mp3
    • big_ben_3.mp3
    • big_ben_4.mp3
    • big_ben_5.mp3
    • big_ben_6.mp3
    • big_ben_7.mp3
    • big_ben_8.mp3
    • big_ben_9.mp3
    • big_ben_10.mp3
    • big_ben_11.mp3
    • big_ben_12.mp3
  • big_ben_12.mp3

Sunday, November 9, 2014

Twitter Logger with Python

Want a more modern method for simple logging and notifications? Twitter is very popular, but it normally too "noisy" for me to follow for social messages. Add a bit of tech and now I have a reason to check Twitter at least once a day, or follow the events on my phone.

I had read articles in both Linux Journal and The MagPi Magazine about engineering minds using Twitter to receive notifications when certain events occur. I decided to take this a step further and create a tiny Twitter logger script for all of my Raspberry Pis. I now receive notifications for all kinds of events, such as:

  • Daily "alive" notifications
  • Reboots, power cycles
  • Changes in dynamic IP address
  • GPIO event triggers (think security alarm, garage door, sprinkler system, etc)
  • And anything else that fancies me at the moment


How complicated is the Python? Easy. Only 3 lines (ignoring the line wrapping and commented debug code):
import twitter

api = twitter.Api(consumer_key='XXX',

status = api.PostUpdate('This is my status update')

# print status.text

To use this code you will need to first generate your Twitter App API Access Keys and also install the python-twitter Python package.

Twitter App API Access Keys

Step 1 - Twitter Account: So how does one get started?  Well first, you need a Twitter account.  I assume you already have one, or at least don't need help creating one.

Step 2 - Mobile Phone: Unfortunately, your code will only be able to read status updates, unless you tie a mobile phone number to your account. Once you have validated your mobile phone, you will then be able to write/post status updates as well. Go to your account Settings and select the Mobile section. Add your mobile phone number, and wait for the validation code to appear on your phone. (note: I did attempt to try a couple of free burner mobile phone numbers, none of which ever received the validation code)

"You must add your mobile phone to your Twitter profile before granting your application write capabilities. Please read for more information"
Step 3 - Twitter App: Next, we need to create a Twitter App. This is nothing more than a method to get access to your api keys. Browse to and click the "Create New App" button.

Fill in the Name, Description and Website fields, then accept the agreement and continue.

The important field is the Name field as it has to be unique among all Twitter Apps. I just used my twitter account name, as I assumed no one else would be using that for an app name.

The Website field has to be populated, but won't be used. Put some temporary website and continue.

The Callback URL can be ignored.

Step 4 - Access Level: After the Twitter App has been created, find the Application Settings section and modify the Access level option by clicking the Modify App Permission link.  Change the access level from Read Only to Read and Write.  If you receive a warning about your mobile phone number, go back to step 2.

Step 5 - Access Keys: Finally, find the Application Settings section again and click the Manage Keys and Access Tokens link. You will find the consumer keys at the top of the page. Under the Your Access Token section, click the Create My Access Token button to generate the access tokens. If it isn't obvious the keys match the code variables as such:
consumer_key = "Consumer Key (API Key)"
consumer_secret = "Consumer Secret (API Secret)"
access_token_key = "Access Token"
access_token_secret = "Access Token Secret"

Now with your access keys, you can begin using the code above to update your twitter status with various notifications.


The python-twitter package "provides a pure Python interface for the Twitter API." To install the python-twitter package, simply use pip.
$ sudo pip install python-twitter

That was easy.

Check Status Code

The previous code showed how we can post a new update, but what about getting our current status, or someone else's?
import twitter
api = twitter.Api(...)

# get my timeline
statuses = api.GetUserTimeline()

# get a specific user's timeline:
# statuses = api.GetUserTimeline(screen_name=SCREEN_NAME)

# show latest message only:
print statuses[0].text

# show all returned messages:
for s in statuses:
       print s.text

Catch Errors

There are a few important errors that you will probably run across, and should handle:

Authentication failure: (check your keys, especially for accientally copied space characters)
twitter.error.TwitterError: [{u'message': u'Could not authenticate you', u'code': 32}]

Too long of a message: (shorten your message)
twitter.error.TwitterError: [{u'message': u'Status is over 140 characters.', u'code': 186}]

Duplicate message: (don't repeat messages or add a unique id, like time)
twitter.error.TwitterError: [{u'message': u'Status is a duplicate.', u'code': 187}]

User does not exist: (check the user name you are trying to query)
twitter.error.TwitterError: [{u'message': u'Sorry, that page does not exist', u'code': 34}]


I updated the twitter script to accept a message from the command line, and then added it to my cronjob:
@daily      /usr/bin/python /usr/local/bin/twitter alive
@reboot     /usr/bin/python /usr/local/bin/twitter reboot


#1 To be able to group and sort messages, I would recommend using the power of the hashtag. Pick a unique identifier (maybe your username) and append a category like this:
system startup #oeey_garage_pi

#2 To avoid the "Status is a duplicate" you may also wish to append a unique ID to all messages. I like to use the current linux epoc time, like this:
system startup #oeey_garage_pi (1415571010)

The updated posting code would look like this:
import time
status = api.PostUpdate('{message} #{category} ({id})'.format(


/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see InsecurePlatformWarning
Solution: either ignore the warning or upgrade to at least Python 2.7.9 (or change code to use pyOpenSSL).

Other Libraries

If Python is not your thing, there a number of other Twitter libraries for various other programming platforms.

That's All Folks

Good luck, and have a good time playing with Python and Twitter.