assignment: To modify the circuit board and assembly code from last
     week so that the board could send and receive data and blink an LED.

     details: This project, despite its apparent simplicity was much more
     difficult as it entailed learning much of the software that was
     transparent to us last week.

     Beginning with Eagle, I had a lot of difficulty making the connections
     in the .brd file. Ultimately I realized that this was because the  grid scale
     was set too high by an order of mag and as a result the program would not
     snap to the desired pin connections. Once I had resolved this issue
     completing the .brd file was simple. For the actual layout I synthesized
     the .sch files from two other boards that were posted on the class site,
     one that blinked while sending data in the fashion of the first board
     and another that was designed to receive and send back an incremented
     character. Links to the .sch, .brd and .cmp files are included at the 
     bottom of this page. An image of the completed board appears below.


     Of note, my original routing of the circuit was incorrect. To correct
     the board I used tweezers to scratch out one of the milled connections
     and used a wire to jumper the correct circuit.

     Revising the assembly code was also fairly straightforward. I simply
     cribbed code from the two boards described above. One difficulty I had,
     and that led to hours of fruitless troubleshooting, was that I had 
     misidentified one of the board pins and as a result the LED was not 
     operating as I had expected. Once I corrected the assembly code the 
     LED began to operate correctly. One additional modification I made to
     the assembly code was to reverse the order of the sbi and cbi commands, 
     resulting in short blinks with long pauses rather than long blinks
     interupted by short pauses. Links to the .asm and .hex files used in this
     project appear at the bottom of the page.
     A screen caputer of the python interface is shown below, demonstrating
     the incrementation of the input character.


     -> .sch of new board

     -> .brd of new board

     -> .cmp of new board

     -> .asm of new board

     -> .hex of new board