After publishing text about the CyberCard project I got the question from a friend. Wasn’t it cheaper to buy Jeff Mayes’ interface driver then to build my own?
Answer is yes – at $30 that board is cheap. But that’s not all. Even the original RMCARD205 at $150 is cheaper than what I spent.
First of all, there were 4 revisions. The first revision was a bit too large. Manually filing PCB did the trick for the troubleshooting but I wanted to have revision B with the correct width. While width was now correct, I accidentally shortened it a bit. And yes, this brought me to the third revision. For that revision I also changed MCP2221A to SOIC package. It wasn’t strictly necessary but I figured having all three ICs in SOIC looked nicer than having different package styles on the same board. The last revision D was just a bit more fiddling with design without any major change. Yes, there were some other changes but this was a gist of it.
Considering each revision was around $25 in PCB cost (OSHPark) and I spent about $50 in parts for them, project was more expensive than official RMCARD205 even without accounting for my time. Since the first version was actually working, you can view all the time and money spent afterward as wasted.
But I disagree. From the moment I started working on it I knew it would end more expensive than the original part. Even for the first board I spent more money in PCB and parts than what Jeff’s adapter would cost with shipping. I found this board to be the perfect project: it would result in something useful, it was simple enough that I could work with it whenever I had some spare time, cheap enough that it wouldn’t break the bank, and an excellent chance to setup PIC16F1454 as an USB device.
I was eyeing PIC16F1454 for a few years now (I still have sample from Microchip from when it was originally announced) but I never got around to. When I first started with the board design I noticed MCP2221A USB-to-serial bridge was compatible with 16F1454’s footprint. If I was a betting man, I would have said that MCP2221A was nothing other than PIC16F1454 with the custom code. This project gave me a reason to get into this interesting PIC and do some USB programming.
I actually paid not for the final board – no matter how well it works. I paid a good money to keep me entertained and to fill my free time. And it was worth every penny.