Embedded systems are often constrained by their energy consumption. To create energy-efficient software or to validate worst-case energy behavior, sophisticated energy models can be used. Measuring the energy consumption of a processor on a fine-grained level for an energy model typically requires the design of custom measurement hardware. In this paper we present a simple measurement setup using the on-chip ADC of a TriCore AURIX TC277 multi-core processor, utilizing one core as a measurement core without the need of external or additional HW. We show that with this setup, a reasonable level of accuracy can be achieved. Furthermore, this also enables on-line power measurements and energy-aware decisions for, e.g., mixed criticality systems.