Paul van Gerven
27 June 2022

Advancing on their dream to rid internet-of-things devices of batteries, researchers at Delft University of Technology have developed “two-way, intermittently-powered Bluetooth.” The technology, dubbed Freebie, continues to work even if the power supply is interrupted, as is bound to happen if the device depends on harvesting its energy from ambient power sources and doesn’t have a backup power supply.

The Delft research group led by Przemyslaw Pawelczak previously developed a system that enables battery-free devices to keep time despite power interruptions. As a demonstrator, the team also created a batteryless 8-bit Nintendo Game Boy clone powered by sunlight and key presses.

Credit: TU Delft

“We want IoT devices to be free of batteries, as these are hazardous, bulky and they have a chemical impact on the environment,” says Jasper de Winkel, co-author of the Freebie paper recently presented at the ACM Mobisys conference in Portland. Intermittent computing allows these devices to perform their essential functions on harvested – and thereby often intermittent – energy alone, without ever losing data. “The things part was already solved. Now, with intermittently-powered Bluetooth, we’ve also addressed the internet part.”

Freebie is extremely energy efficient, says De Winkel. “To maintain a connection using a standard Bluetooth implementation, the Bluetooth chip can be put in sleep mode whenever the IoT device is idle. By saving the exact state, however, we can switch the chip off completely, reducing energy consumption by an order of magnitude.”

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The researchers achieved their energy-efficient implementation using commercially available hardware. Pawelczak: “Should we integrate our solution on a dedicated system-on-a-chip, we would then be able to provide the most sustainable, low-power Bluetooth implementation available on the market.” Additionally, unlike previous frameworks for battery-free communication, Freebie is bi-directional, enabling firmware updates and remote device configuration.

Major Bluetooth chip suppliers have already shown interest, TU Delft reports in the press release.