This week, we learned Electronic Design Automation (EDA) tools, including Eagle, one of the most commonly-used EDA tools among amateurs because it's free and there's a large online support base. I'd learned to use Eagle before in the Harvard fab lab in order to design a simple board using the ATtiny45, so I was already familiar with the tool.
The finished "Hello World" board: My main success for this week was in designing and milling this board, which will (eventually) be able to turn on an LED when you press the button.
First schematic: This is the original schematic I made for the Hello World board--I've since only changed it to add labels for signals and add supply symbols.
The first step in Eagle is to make a schematic. The system is mostly veyr simple and clear: You choose parts from a list, place them, and put wires between them. Because Eagle is old and the GUI is really poorly designed, the tools don't tell you their names when you mouse-over (unless you wait 10 seconds), and Eagle can't have two tools named the same thing, so the tool for making connections in a schematic is called "net" (instead of the obvious "connect" or "wire").
First board: My first attempt at designing a board was moderately successful. In the end, I had to redo the board outline on another layer (to prevent the outside having an extra line), but got to keep most of the board.
Battery charger schematic: I used an ATtiny45 in a buck topology as a voltage/current regulator to limit the battery charging current/voltage; a sense resistor (maybe 0.1 ohms) senses current while the microcontroller directly senses topside voltage.
Design rules check: My second board for the week, the first attempt to design a Li-Ion battery charger, also went pretty well. There were a couple things that originally failed the DRC, but after fixing those it only complained about my overlapping pads from the mini-USB jack and makeshift pads (for jumpers and unknown inductor pads). I realized that in future I'd need to fix the made-up pads and jumpers, as well as giving the higher-current parts larger traces
As with the schematic tools, Eagle's poorly-named tools were inconvenient in making the board (also, the fact that it lacks simple drawing tools, which would be useful for making boards with any geometric complexity).