The averse reaction of lithium batteries inspired researchers to look for alternat-
ives for energy storage in electronics. Battery-free or intermittent devices intro-
duce a new paradigm with their own specific problems about power, state track-
ing, timing and communication. We implemented the battery-free paradigm in
the Thread protocol, utilizing the specific characteristics of End Devices in the
mesh network to reduce power consumption. The intermittent implementation
is fulfilled without changing the behaviour of the protocol, making the device
fully compatible without other devices being aware of the intermittent opera-
tion. During tests four implementations are tested, completely naive, semi naive
with simple power improvements, Sleepy End Device operating intermittently
and a Synchronised Sleepy End Device operating intermittently. The results of
the power measurements are used to determine the feasability of four use cases.
The intermittently operating Sleepy End Device is out performing the Naive
and Semi Naive implementation.

Batteryless Internet of Things (IoT) devices powered by energy harvesting enable sustainable and maintenance-free operation, but face challenges in achieving synchronised bidirectional communication between intermittently-powered nodes. This thesis presents CardioSync, a novel framework that leverages the human heartbeat as a shared clock to synchronise Bluetooth Low Energy (BLE) connections between battery less devices. CardioSync integrates a low-power optical heart rate sensor to capture real-time heartbeat data. A peak detection algorithm identifies distinct heart rate peaks, establishing synchronisation points for connection-setup events. By scheduling BLE advertising and scanning activities timed with detected peaks, CardioSync aligns connection attempts between intermittently-powered devices. This heartbeat-based synchronisation is integrated into the existing FreeBie architecture for intermittent BLE communication. Experimental evaluations demonstrate CardioSync's ability to successfully establish synchronised connections between batteryless nodes, reducing average connection setup time by up to 1.8x compared to an asynchronous FreeBie system. However, these gains incurred increased power consumption due to the integrated sensor. CardioSync enhances FreeBie's capabilities, enabling efficient intermittent-to-intermittent BLE connections. The proposed technique shows promise for advancing body sensor networks through sustainable and maintenance-free operation. Further work should optimise sensor utilisation and explore adaptive synchronisation to improve energy efficiency.

This work presents the first robust connection mode for Bluetooth Low Energy on an energy harvesting sensor.

Debugging and testing battery-free intermittently-powered systems is notoriously difficult. This is not only due to the additional complexity of maintaining state through power failures but also due to the lack of proper tools to test and debug these systems. As a solution, we present DIPS: a fully-featured hardware debugger for battery-free intermittently-powered systems capable of automatically verifying memory and peripheral state between power failures. Our solution seamlessly integrates an emulator allowing for emulation of any power scenario to the device under test. This allows our debugger to pause emulation and program execution when debugging or when state restoration issues are detected. Our new system is built around GNU Debugger (GDB): a widely-used debugging tool. Therefore, DIPS allows for a debugging process identical to state-of-the-art debuggers for continuously-powered devices. User studies found that our debugger is easy and intuitive to use. It allows embedded system developers to find bugs quicker in code written for battery-free devices. Users evaluate our debugger and we have found unseen errors in a state-of-the-art software framework for intermittently powered systems.

This thesis proposes an ultra-low-power architecture for wireless Internet of Things end devices. The architecture enabled a prototype that can run a mainstream wireless protocol with an extremely limited power budget.