I am just wondering about the internal voltage reference which is usually 1.1V ATmega168/328 chips, is that present in the spark core?
The reason I ask is because I will be running the spark core on battery, and I will like to run an accelerometer on it for a week. As the battery starts getting emptier, the reference voltage (~3.3V, which is not accurate to begin with) will probably start dropping. This might give me more and more inaccurate results by the day (I need it to be very precise for my purposes), so I would need a reference voltage which I can trust and I can adjust my accelerometer readings according to.
Does anyone know if there is an accurate internal reference? If not, how could you do it?