add comments on the inner workings of the msp430 energytrace library

        bin_count = args.histogram

        # On an MSP430FR5994 launchpad, energy is measured and reported with a

        # granularity of 200 / 300 / 400 nJ per pulse. Details are unclear.

        plt.title("EnergyTrace Data Analysis")

        plt.xlabel("Reported Energy per Measurement Interval [J]")

        plt.ylabel("Count")

        plt.hist((data[1:, 3] - data[:-1, 3]) * 1e-9, bins=bin_count)

        plt.show()

        # Data is transferred using a URB_BULK endpoint with five samples

        # per USB packet. There's about 1.4ms between consecutive packets

        # and 210 to 270 ms between most consecutive samples. The first sample

        # in a packet typically has a larger delta-t of ~400ms vs the last

        # sample in the previous packet.

        plt.title("EnergyTrace Data Analysis")

        plt.xlabel("Measurement Interval Duration [s]")

        plt.ylabel("Count")