There’s a Maker Faire in three weeks, and your group wants to design and build a binary watch to give to attendees. You don’t have much time, and your budget is $3 per watch. What do you do? If you are [Parker@Macrofab] you come up with a plan, buy some parts, and start prototyping.
[Parker] selected the PIC16F527 because it had enough I/O and was inexpensive. A cheap crystal and some miscellaneous discrete parts rounded out the bill of materials. Some cheap ESD straps would serve for a band. He did the prototype with a PICDEM board and immediately ran into the bane of PIC programmers: the analog comparators were overriding the digital I/O pins. With that hurdle clear, [Parker] got the rest of the design prototyped and laid a board out in Eagle.
A few of [Parker’s] optimizations (that is, cost cutting moves) didn’t work out perfectly, so he had to make some last minute circuit changes. Worse still, the ESD straps got hung up in customs, necessitating a last minute swap to a different band. This broke the $3 budget but c’est la guerre.
In the end, [Parker] had a practical watch to give away. It might not have been perfect, but as you can see in the video, it came out great, especially considering the short time frame. It won’t replace a homebrew smartwatch, and it won’t decode secret messages, but then again those don’t cost $3.