Following up from the fabISP project, this week the assigment required us to take a little more control of the design by redrawing the "hello world echo" board and adding (at minimum) a button and an LED.
The ISP project was my first experience working with circuitry and SMT, so I decided to focus on fundamentals. My major objective for this assignment was to get comfortable with EAGLE for drawing and mapping out boards. Two additional goals were to create a teaching object that could be played with (a general theme of my projects), and also to follow-up on a prototype design I made in Sketchup for the ISP, where the board would be sectored into several pieces that assembled in 3-dimensions. Besides being novel, it would be compact, protected from the elements, and revealing of the internal circuitry to curious minds (I might have been channeling the fact that I owned a transparent GameBoy when I was younger... who am I kidding, I still own it).
After attending the recitation on EAGLE and reading a few of the tutorials on the FAB site and Sparkfun, I decided to first practice by backwards-engineering the fabISP from the traces we were given in class. On this first go I used the net function to link all of the components together. This worked, but the solution looked messy and ineligant.
After that attempt I reviewed my notes from the Electronics Design 101 tutorial and some of the previous year's design pages, and realized that it would be easier to create (and read) schematics by giving connecting nets the same name, which would virtually link them together. This creates a cleaner schematic, and one where functional groups of components can be separated, labled, and more easily digested and debugged. The second attempt at the ISP was much more satisfying.
I also attempted to create my own board layout for the fabISP, but after puttering around for an hour with the route tool for laying traces, I discovered that it's quite difficult (and gained a newfound appreciation for the elegance of Professor Gershenfeld's design). Desiding I had bigger fish to fry, I moved on to designing my own board.