In case it might be of use to someone, I've posted a Youtube video and created a Github repo dealing with an alternate way of multiplexing 7-segment displays that has a greatly reduced parts count. It's multiplexing by segment instead of by digit. The video shows this method implemented with an MSP430G2553. The Github repo has demonstration Arduino Nano sketches, but they should work as-is with Energia except for the pin assignments. The video is on my local OSH group's channel, and I can't respond to comments there, but will answer questions here if there are any.
https://www.youtube