Power Analysis: Probing WS2812 RGB LEDs #NeoPixels
Power analysis is a technique to probe the inner workings of an integrated circuit by measuring changes in the supply current. Whenever a logic gate switches, it will cause a tiny current spike that can be measured externally. By inspecting the temporal variation, especially in reaction to an external signal, it is often possible to deduce information about the construction of the IC.
You can see my setup in the photo above and the schematic diagram. The WS2812S sits on the right breadboard. I used exactly the same device that I investigated previously. I used an ATMega168 to generate stimulus signals. The series resistor smooths the signal on Din (ch1) to reduce noise injection to the DUT from the MCU. Finally, the current consumption is measured with a 47 Ohm shunt resistor on the positive supply (ch2). The entire setup is surely far from ideal – bread board parasitics are no joke – but it worked well enough.
You can see the analysis and some very interesting conclusions in the post here.
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