本篇論文描述一個名為EcoMicro並具有能量擷取能力之微小型無線感測節點。 此感測節點具有9軸慣性感測器可以量測物體的姿態與轉向，且經由低耗藍芽(BLE)通訊協定作為與其他裝置溝通的媒介。 感測節點是藉由小型太陽能晶片、最大功率追蹤技術(MPPT)以及可重複充電之能量儲存元件來提供自我供電之能力。 系統架構中也包含了一個時鐘日曆晶片(RTC)用來紀錄時間與作為能量管理的中樞。 本篇論文中的實驗結果證實EcoMicro可以有效率且正確地運作在一些需要小體積且有能量受限因素的應用中，突破了這些應用在之前類似的系統因上述原因而無法有效地達成的限制。

This thesis describes EcoMicro, a miniature, wireless sensor node with energy harvesting ca- pability. It is capable of measuring motion using a 9-DoF (degree-of-freedom) inertial sensor and communication over Bluetooth Low Energy (BLE) protocol. It is self-powered by a solar cell using a maximum power point tracker (MPPT) and a rechargeable energy storage suited for energy har- vesting. The system also includes a real-time clock (RTC) for not only tracking time but also for power management. Experimental results show that EcoMicro to operate correctly and efficiently for a class of wireless sensing applications where the previous system failed to apply due to size or power constraints.

Contents i
Acknowledgments v
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Related Work 4
2.1 Energy Harvesting System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Maximum Power Point Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 System Overview 7
3.1 System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Power Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.1 Solar Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.2 Power Management Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.3 Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3 Controller and Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3.1 MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.2 Secondary Bootloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.3 Over-the-Air Update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4 Dynamical Advertising Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5 Peripherals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.5.1 Real Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5.2 9-Axial Inertial Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4 Power and Energy 17
4.1 System Operating Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.1 Off Load State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.2 Normal State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2 Solar Cell P-V and I-V Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 System Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.4 UMAC Self-Discharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5 Evaluation 26
5.1 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.2 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2.1 Operation without the 9-DoF Inertial Sensor . . . . . . . . . . . . . . . . . . 29
5.2.2 Operation with 9-DoF Inertial Sensor . . . . . . . . . . . . . . . . . . . . . 30
5.2.3 RTC countdown timer vs. Da14580 kernel timer power consumption . . . . . 32
5.2.4 Dynamic Advertising Cycle Packets and Duration . . . . . . . . . . . . . . . 33
5.3 Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.3.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
6 Conclusions and Future Work 36
6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
A Schematic and BOM 42
B Source code 46

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