Hackpack v3
Hackpack v3 was part of the badge for Signal 2017.
It consists of a custom PC board with a socketed Particle Electron, a Lithium Ion battery, and 16 Neopixel LEDs.
Now that I am home, I am experimenting with it.
You can program it entirely via the Particle web site, or you can download Particle's fork of Atom, and use it to edit code. Atom is a Github product so as you might expect, your code gets stored in Github. Then you can compile the code (on the Web) and then you can flash it into the Electron.
I am trying out Atom right now. I installed it on my Mac.
Hello World
See the code and some variants at https://github.com/twilio/hackpack-v3
Hardware details
I want to be able to detect when external power is connected and disconnected. External power will be an automobile, so I want to know when the car starts and is shut down.
BQ24195 power management unit and battery charger (pdf data sheet) Refer to section 8.5 to find out about i2c communications with this device. You can poll it or accept interrupts from it; when you get an interrupt, read the fault register to clear it.
Q. Is the interrupt line connected on the Electron board?
MAX17043 fuel gauge (pdf data sheet) This chip has some registers you can read to find out the state of the battery. You can put it to sleep to save power by dropping SDA and SCL for at least 2.5 seconds.