Video & First Program

Finally, I have gotten around to doing an unboxing video. There are tonnes of these on youtube already, but this mine. I have re-imaged the SD card with the Debian OS again just to give a sense of the setup procedure, so the video goes through unboxing, to first boot into the GUI environment. Enjoy!

First Program

I have also written a first Python program since the operating system comes pre-installed with Python.  Rather than going with the default Hello World! program, I tried to challenge myself by writing a program which will check a user's PPS number - this is the Irish Personal Public Service Number which comprises 7 digits followed by a check character, which is derived from a mod23 checksum.

I won't be getting a job programming the next generation of Space Shuttle, but at least it is a little more meaty than the pythonic Hello World:

print "Hello World"

There are probably better ways to implement this script, but I'm happy enough to pass it off as a first attempt to program on the RPi.

ppsn.py

# Initialisation of variables
sum = 0
letters = "WABCDEFGHIJKLMNOPQRSTUV"

# Set loop condition
done = False

# Loop until valid input is received
while not done:
 ppsn  = raw_input('Enter a PPSN to check: ')
 
 # Check for correct length 
 if (len(ppsn) == 8):
  # Check that first 7 characters are numbers
  if ppsn[0:6].isdigit():
   # Last character must be alphabetical
   if ppsn[7].isalpha():
    done = True
   else:
    print "The last character must be a letter"
  else:
   print "The first 6 characters must be numbers"

 else:
  print "The PPSN must be 8 characters in length, i.e. 7 digits & 1 letter"

# Checksum
for i in range(0,7):
 num = int(ppsn[i]) # cast num to integer type
 sum += num * (8-i)

# Get mod23 of sum to get position of check character
mod = sum % 23

# Correct for modulus equal to 0 
if (mod == 0):
 mod = 23

# Output results
if (ppsn[7] == letters[mod]):
 print ppsn + " is a valid PPSN"
else:
 print ppsn + " is not valid"

The output screenshot is from a SSH session into the RPi - the OpenBSD Secure Shell is disabled on startup by default, but can be easily enabled as follows:

sudo mv /boot/boot_enable_ssh.rc /boot/boot.rc

Output of first program written on RPi in Python

Next steps:

Course related:

• Re-install web server (apache)
• Re-install RDBMS (mysql)
• Install Ruby on Rails
• Git???

Other:

• Install OpenCV
• Get a webcam working, then get a second one working
• Write a dissertation on Stereo Image Object Extraction