Power Profiler for Accelerated Embedded Hardware Development

Streamlining the Development Process with Efficient Power Analysis

- Matthew Oppenheim

This article demonstrates how to use a power profiler to extend the battery life of embedded hardware and how Matthew used the profiler for debugging.

A power profiler is an instrument that accurately measures the power that your device under test (DUT) uses in real time. This allows us to see how the changes to the hardware and firmware on our latest embedded project affect the power that our device uses. In this article I explain how I used the Nordic Semiconductor Power Profiler Kit 2 (PPK2) [1] to significantly improve the battery life of a wearable assistive technology project. The profiler also played a major role in debugging when the hardware was misbehaving. A power profiler gives an extra channel of information as to what the hardware is doing in addition to our usual debugging tools. By monitoring how the current varies in a microcontroller, security experts such as Colin O'Flynn can even extract enough information as to what the internals of the microprocessor are doing to crack the encryption of supposedly secure data, described in his article "Side-Channel Power Analysis" (Circuit Cellar #344, March 2019) [2].

ENTER THE PPK2

Figure 1 shows the PPK2 connected to a Lilygo T-Watch S3 that I used for the project presented in this article. More on this programmable smartwatch later. A friend introduced me to the PPK2. He is lucky enough to have his employer supply the instrument. I bought mine for around $100 so it is not prohibitively expensive. I found more expensive power profilers with extra features, such as the ability to vary the output voltage and current to mimic a discharging battery. I can't justify paying the extra for this functionality.

The PPK2 powers the DUT and connects to a PC or laptop by a USB cable. The PPK2 is controlled from your PC using a software graphical user interface (GUI). I'll explain how to download and install the software later.