Electronics Design

Drawing

This week I got to draw my own board! Initially I found this to be extremely frustrating, but in the end, it ended up being fun!

To start, I downloaded KiCad. I decided to use this instead of Eagle because I try to use free software as much as I can. I did not know, my the downloading process takes a long time, so prepare accordingly.

Before even starting to draw, you need to install the fab libraries. This was not the most intuitive process, since you need to do it for the schematic and pcb view. First, open a new project to the schematic view. Then go to Preferences -> Manage Symbol Libraries and click on Append Libary to add the fab.lib file. Then, in the PCB view, you have to add the footprints. To do this, go to Preferences -> Manage Footprint Libraries. Then click Append Library to add the fab.pretty folder.

Once KiCad got downloaded and set up, it was time to draw. I had no idea what I was doing, so I asked a lot of questions. I looked at this board to get started. However, I had no idea what the components were. Through many questions, I discovered the following mapping:

• IC1 - ATTiny44A-SSU
• J2 FTD1 - FTD1 SMD Header
• LED - 1206
• XTAL1 - EFOBM
• J1 ISP - AVR-ISP-6

I started with these components, and then added in an LED (PB2) and the resistors. Per suggestion, I added a 10K resistor to both the led and the switch. At first, I had no idea how and where to connect things to ground, and voltages. But slowly but surely following the wires in the diagram, I connected the network structure, as seen below.

The next task is to set the components parameters. This means to set the reistance level and capacitance for all the components. I wasn't sure which components needed this, so I just clicked on every component. To do this in keycad, you double clik inside the component on the schematic view, click the Value field, and fill in the Field Value text box. Next, you have to set the footprints of the components.

Milling

We had to mill the board a couple times because the traces were too small. First, we cut the traces, and then we cut the outline.

As you can see, on the first mill (top), the traces are very thin. So I went back into my kiCAD file and changed the track to .4mm or 15.75 mills. This resulted in a thicker trace, which is seen in the second mill (designated by the 2 in the penguin on the board.

Soldering

Next, I picked out the components and started soldering from the most difficult part (the ATTiny) and moving outwards on the board. I used the copper braid to fix some solder problems.

Not So Fast!

After trying to power on my board multiple times, I continued getting a flashing red light on the avrisp2 programmer. At first, we thought it was a problem with the capacitor, which I replaced. That didn't work. Then I resoldered a bunch of the connections on the 2x3 connector. That also didn't help.

Finally, with the TAs, I figured out that I made a mistake in the design process. There was a not a connection between pin 5 on the ISP and pin 6 on the ATTiny. I was scared I was going to have to start over, but instead, we soldered a jumper (a wire) between them.

It's not pretty, but it worked!

Testing

Since I have a mac computer with USB-C ports, I needed to use someone else's computer to program my board. We following the programming instructions here and it worked!