A hardware hacker named [caspar] demonstrates using NFC energy harvesting to wake and command a Raspberry Pi Pico W from a smartphone. The MCU is kept fully unpowered (not just sleeping) via a transistor, with only leakage current draining the battery. An ST25DV04KC NFC chip, powered entirely by the phone's NFC field, receives commands and wakes the Pico via GPIO, passing commands over I2C. A live antenna-tuning script runs on the Pico itself. The technique is also applied to an e-ink display that operates without any battery. This project is an entry in Hackaday's 2026 Green Power Challenge 'anything but PV' category.
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