I’m live with the Lets Encrypt certificates for the blog.mcgarrah.org website. This has been awhile in the making and I’m kind of excited. I’m on a legacy environment with Ubuntu 12.04 LTS so part of the process is manual but certificate update just happens nicely. Updating the Apache config files has a little bit of effort but nothing too bad.

Artificial Intelligence for Robotics (CS8803-001)

Associated with Georgia Institute of Technology

Fall Semester 2015

The goal for the final project in CS6475 AI for Robotics was to create a robotic platform to investigate computer vision technology. The platform included an Arduino with sensors and motors and a Raspberry Pi 2 for the vision and primary control system. The project URL is a video channel that shows the progress and challenges.

For an assignment in my robotics class, I need to have an autonomous system react to the environment around it. Reacting can be as simple as flashing a LED if a sensor detects a change.

I have two objectives for the Raspberry Pi 2 (RasPi2) and those are to take a picture using the 5mp webcam and flash a LED. I could use the standard GPIO pins and setup a separate LED but noticed we have two perfectly good LEDs built into the board.

Reading on these built-in LED did not elicit any clear way of interacting with them from the regular Linux documentation. I informally called them the Red Power and Green DiskIO LEDs. It was by reading the headers to the source for Windows 10 for Raspberry Pi 2 that I found the GPIO pinouts for these two LEDs. They are:

35 Red Power LED
47 Yellow DiskIO LED

I needed a quick understanding of the Python 3.3.0 datetime functionality to do a difference in times across days. Python make it amazingly easy.

import datetime
from datetime import timedelta

# get current timedate
now = datetime.datetime.now()
print "now: " + str(now)
# get one day of time oneday = timedelta(days=1)
# make one day in the future and past
tomorrow = now + oneday
yesterday = now - oneday
print "tomorrow: " + str(tomorrow)
print "yesterday: " + str(yesterday)
# compare times
if now < tomorrow:
  print "now < tomorrow"
elif now > tomorrow:
  print "now > tomorrow"
else:
  print "now must be equal tomorrow"
if now > yesterday:
 print "now > yesterday"
elif now < yesterday:
 print "now < yesterday"
else:
 print "now = yesterday"

The expected results are:

CMD> python time.py
now: 2015-03-19 14:30:31.083000
tomorrow: 2015-03-20 14:30:31.083000
yesterday: 2015-03-18 14:30:31.083000
now < tomorrow
now > yesterday

I hope this helps someone.