First Bytes 2013

These lights are also capable of displaying messages. If you choose, you can program the lights to display a message and compete in the message categories. To do this task, you would need to choose a phrase and then program your lights to write letters to spell out that phrase. (Be sure to follow the rules of the competition!) As an example, these lights are scrolling a message.

To help you, we have provided a message framework (called message_framework and available on your USB drive). This message framework has essentially the same files and setup as your pattern framework, but it does differ in some important ways:

• In your pattern framework, the bulbs are addressed from 0 to 15. This framework instead assumes that the lights are situated in a 3x5 grid with an extra bulb at the bottom right (such as the one in the video above) and that the grid is wired as follows:

  15   10    5
  14    9    4
  13    8    3
  12    7    2
  11    6    1
             0
  

  (Don't worry! We will help you get this set up correctly!) In the framework, then, the bulbs are addressed using their (x,y) coordinates beginning from the upper left hand corner (this is typical for graphics in computer science) as follows:

  (0,0)   (1,0)   (2,0)
  (0,1)   (1,1)   (2,1)
  (0,2)   (1,2)   (2,2)
  (0,3)   (1,3)   (2,3)
  (0,4)   (1,4)   (2,4)
                  (2,5)
  

  Therefore, when you refer to a bulb in this framework, you will refer to it using its (x,y) coordinate rather than its position in the strand of lights.
• When you programmed the patterns, you worked with the data structure strand which was a 1D-array representing the lights. strand was later mapped onto the live lights using strand_mirror().
  
  This framework has a similar setup. The grid data structure, a 2D-array representing the lights in their new configuration, holds the values for the lights, and then that data structure is reflected into the live lights using grid_mirror(). Like strand, grid has some extra spots to enable scrolling.
  
  Additionally, this framework has another data structure, letter. The letter data structure is similar to grid except that it holds ints rather than pixels. letter provides a simplified way to set the bulbs to a particular color or to turn them off (more on how to represent a color as an int below), and then its data is reflected into grid which is then reflected to the live lights. Programming of the letter data structure takes place in the letters.cpp/h files.
• Additionally, some files in this framework vary from those in the patterns framework. Files protocol.cpp/h have been changed to reflect the new addressing. You should not need to change these files. grid.cpp/h replace lights.cpp/h, and strand_mirror() and strand_scroll() have been replaced by grid_mirror() and grid_scroll(), respectively. The color files have also been replaced with colors_grid files.
• To represent the colors as ints for the letter data structure, the colors_grid.h file contains the following line of code:

  enum {WHITE, RED};
  

  This line is known as an enumeration, and it simply sets up named integer constants, so that WHITE can be used as an integer (and, in fact, represents the value 0) and RED can also be used as an integer (it represents 1). You can read more about enum in C/C++ on this web page.
  
  In this project, the enumerated types are used to indicate the desired color in many of the given functions. You can easily add your own colors to this enum, so feel free to try it on your own or ask for advice.
• In this framework, most of your coding will be done in letters.cpp/h. These files contain some predefined code (some of which is explained next, but most of which are defined by comments in the .cpp file) and define the letter data structure.
  
  There are two important predefined functions in this framework: print_message() and print_letter(). print_message() displays the given message to "screen", one letter at a time, by calling print_letter(). print_letter() has three letters defined for you: A, B, and C. These functions are well-commented, so look over them carefully and be sure you understand what they do before you begin coding. Please ask if you need help our would like to verify your conclusions.
• Note that the framework currently displays a message but does not scroll it. If you would like to scroll a message (as the video does!) grid_scroll() is provided, and both letter and grid have extra columns.
• One final note: you'll need to reset the addressing of the lights, and the lights are only addressed at start up. So, unplug your lights, upload your message program, and then plug in the lights while holding down the reset button. Voila! Your lights have the correct addresses.

Happy Texting!