With the main component of the watch being chosen, it’s now time to choose everything else that will go into making this watch. Since I chose a higher end screen, I’m going to shoot for other nicer components in order to get the most functionality out of it.
First off is the processor. I chose an Atmega32u4 for several reasons.
- I’m very familiar with Arduino and AVR programming, plus the Arduino community has phenomenal support so I wanted a chip that was also on an Arduino board, namely the Atmega328p or Atmega32u4.
- I chose the Atmega32u4 because it has more pins, more memory, more Flash, and a built in USB core which would mean no extra chip required for USB programming. The extra memory and Flash are also a plus since graphical programming result in a pretty large memory footprint.
- As an added plus, the Atmega32u4 has a way to internally change the processor speed so if it becomes an issue, I can speed up the chip when I need a speed boost.
For the Bluetooth 4.0 module I chose a module from FastTech mostly due to the fact that someone had already done all of the hard work, making an eagle component and breakout board.
I also decided to use this accelerometer from Sparkfun since it was the cheapest that they have and also has orientation and shake interrupts that I foresee using in the watch.
I decided to use this vibration motor from Sparkfun since it was already in their eagle library and I was making a purchase from them already.
I added the LiPo charging IC found on this board for to charge my battery directly from USB power.
And for the last of the major components I’m using a generic photocell to detect brightness
Aside from that I have a few other minor components such as regulators, headers, transistors, and passive components with a full BOM to be posted later.