Fletchtronics

Well technically this project isn't really my first PCB. That was made back in high school, a 555 circuit that made an incandescent bulb flash. Excitement! When I first sat down last year thinking about making PCBs again, my first thought brought me right back to that etching process. I'd heard of a technique called "toner transfer" that can be used to create boards at home.

However, I have 2 cats and a wife in an apartment to think about here. I don't want to leave lots of toxic stuff laying around the house for the cats to eat and for everyone to breathe.

So, I decided to use an online printed circuit board fabrication house where I can submit my design and get back a nice board without messing with toxic chemicals.

About a year ago I started tinkering with various PCB making software. The one I focused on at first was too tied into a single supplier for my taste. It was some Windows application that sent designs to a PCB fab house server. That was a mistake. If you use a piece of software like that, "shopping around" consists of getting a quote from the place that provided the software. I like more choices.

Several people I know from various online chat rooms suggested learning Cadsoft Eagle. It took a little while to get used to this piece of software. At first, it seemed to rank up there with Blender for worlds most confusing user-interface. However, after getting into it and understanding the flow of the application, I was able to create really neat circuits quickly.

So I practiced and practiced, yet I didn't really want to produce any board I designed early on. Nothing seemed like it had potential.

As you've seen if you've read other blog posts, the first microcontroller that I played with and wrote code for is the Parallax Propeller. While I still love the Prop, the USB support is lacking. So, while shopping for microcontrollers that had some hardware USB support, I noticed Atmel and their AVR, specifically, the AT90 series. I remembered hearing about AVR in relation to Arduino before, but wasn't really sure what Arduino was. I had seen it plenty of times though, on the electronics websites and at Maker Faire. So I joined the #arduino channel on freenode.net.

Shortly after, I made friends with a few folks who share a similar interest as me: classic arcade equipment for MAME and other types of video games. We all noticed how expensive the USB controller boards were, and very quickly after that, the concept of the Petunia board was born. There are two goals. Goal one is to make an inexpensive board with a hardware USB microcontroller that can be produced and retail for less than existing solutions. The second goal is that the board should provide the owner with more power to expand and change the functions of the device. The AT90USB series is perfect because the chip can be programmed over the USB itself. Also, it supports C language. Finally, some AT90USB models (including our AT90USB162) are very low cost.

Petunia PCB

So, after two weeks of talking with my new friends Greg, Chris and Chris about what a small, inexpensive MAME board should be like, an actual board took shape.

The two major components are the AT90USB162 and the MCP23S17 I/O expander. The device uses the 5 volt rail supplied by USB, which should be fine for the type of devices - switches and buttons mainly - that will be connected to the device.

In addition to my new IRC buddies, I can't thank sparkfun.com enough. Their tutorials are first rate.

PCB made better with sparkfun tutorials

If you do no other Eagle tutorials on Sparkfun, do yourself a big favor and at least do the Better PCBs in Eagle. There's some stuff in there that's really not obvious, especially for beginners.

So after tweaking and tweaking and perfecting more and more, and eventually routing the traces by hand, over two weeks a nice little board was born. Right here on the internet! Wow it's useful for something other than porn!

Last weekend, I sent the board to BatchPCB to get four prototype boards fabricated. BatchPCB is another Sparkfun service. I could have made them cheaper possibly somewhere else, but Sparkfun has always been so helpful, and being a complete newbie I felt really comfortable doing business with them.

So, I made the most embarrassing, idiotic n00b loser mistake imaginable. I left off the bottom copper layer. CRAP! In a panic, I send an email asking to cancel the order. Then, in Sparkfun's IRC channel, someone suggests that I upload a new design (you can do that separate from your shopping cart) and ask that BatchPCB simply swap them out before running. So I upload the design and send a second email. Then I notice that I put the order numbers backwards in the second email, effectively asking him to swap out the good one for the bad one again.

It's one of those Zen moments. I stop. Breathe. Wait 30 seconds. Send a final email explaining that I'm the worlds biggest moron and that hopefully the mistake was obvious and that I was moving too fast to try to fix my horrible, horrible mistake. So I spend a tense Sunday, waiting. I figure I'll call first thing on Monday. I try to call at 08:30 Mountain Time, but nobody's there yet.

Moments later, I receive an email. No problem, the good .zip archive with the bottom copper is going to be used. Waves of relief.

The board is on the way!

While it's out being fabricated, those of us back in the IRC channel are busy working on the software and documentation. Stay tuned for Petunia!