msp430-etv: Handle overflows in reported total energy

    data = np.empty((data_count - opt["skip"], 4))

    energy_overflow_count = 0

    prev_total_energy = 0

    for i, line in enumerate(data_lines):

        if i >= opt["skip"]:

            fields = line.split(" ")

                timestamp, current, voltage, total_energy = map(int, fields[1:])

            else:

                raise RuntimeError('cannot parse line "{}"'.format(line))

            if total_energy < 0 and prev_total_energy > 0:

                energy_overflow_count += 1

            prev_total_energy = total_energy

            total_energy += energy_overflow_count * (2 ** 32)

            data[i - opt["skip"]] = [timestamp, current, voltage, total_energy]

    m_duration_us = data[-1, 0] - data[0, 0]

    m_energy_nj = data[-1, 3] - data[0, 3]

    # mV * nA * us = aJ (1e-18 J) -> use factor 1e-6 to get pJ (1e-12 J)

    print(

        "{:d} measurements in {:.2f} s = {:.0f} Hz sample rate".format(