Beginner
First we reviewed some electronics rules with our instructor Federico Vanzati and this helpful page.
I'm not an expert about eletronics, so I found a little bit difficult to understand everything, but I learned behavior mode of a simple LED and a button.
I will use these few rules to calculate value resistor near the LED, so it doesn't break: I will search datasheet of my white LED (I found here)...now I know my resistor value has to be 170 Ohm!
Second step was to open Eagle and to load fab library: in order to have right components, I downloaded the fab.lbr file,I found libraries folder in Eagle, and I made a simple copy and paste; then I went in Eagle's Control Panel, and inside "Libraries" I found my fab.lbr
I started a new schematic: adding components is very simply, you have to go in components list, find the right component seeing "echo hello-world" page, and finally click on "Add".
I started with Attiny44 at center, then I watched component datasheets (often with Google search) and finally I connected them each other with a simple drawn line. Be as "clear" as possible when you position the components, it will be useful to simplifly the construction of the board.
I often used copy/paste for similar components (like resistors), but remember to change the value if you need different working.
For example, here I set capacitor value in 1 uF.
At the end of schematic design, you have to launch ERC command that check your scheme and point out your errors: in my case, it found many errors of overlap between connections and pins; I had to fix them to continue, until there were 0 errors.
Now I have my schematic file and I can switch to the board. Eagle automatically puts all the components on the left out of working area.
I started to move some of them thinking final appearence, but I realized that this approach would complicate the routing. Logical connections with yellow lines are not user friendly.
With the help of my classmate Gianfranco Caputo (thanks!!) I switched to schematic, I checked connections between microcontroller and components, and I positioned components near the right microcontroller pin: for example, capacitor is better on the left of microcontroller so it will be near pin 1 and 14 to which must be connected.
I spent most of the weekend to move components, to change routes, to close and restart the board, but at the end I always needed two bridges with resitors (value 0) to connect ground and supply..2 bridges are too many! I looked at 2015 students archive and EUREKA! I have to draw two routes under the microcontroller (instead of one), and one route where I thought there was no space.
After many many changes and aesthetic improvements finally I have my board with led and button (here brd file).
The last important step was the DRC command, in particular the tab "Clearance": with it you can check if all components are connected and if everywhere there is enough space between routes and components. I set 16mil to be sure.
If there are 0 errors and the preview of milling is good, you can launch PcgGcode(a plug-in of Eagle) that generate the .nc file to operate the milling machine (here my file).
The result is not perfect: the board is too big, and probably in Eagle I used a wrong resonator, because my real resonator is bigger than the schematic one.
I solved the problem by soldering resonator in "vertical" way.