Seven Segment LEDs with Spark Core
Seven segment digit display using a couple of Adafruit backpacks.
Unlike Arduino, Spark Core does not enable internal pull-ups for the i2c lines. So external ones are needed. I happened to have 470Ω around.
With two displays, the second one (on the left) needs to have the A0 jumper shorted to change its address from 70 to 71.