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QuickCal: Assisted Calibration for Crystal-Free Micro-Motes

  • Chang, Tengfei
  • Watteyne, Thomas
  • Maksimovic, Filip
  • Wheeler, Brad
  • Burnett, David
  • Yuan, Titan
  • Vilajosana, Xavier
  • Pister, Kris
Publication Date
Aug 11, 2020
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The Single Chip Micro Mote (SCµM) is a crystal-free single-chip mote that brings us one step closer to the Smart Dust vision, in particular as it can communicate with off-the-shelf IEEE802.15.4 and Bluetooth Low Energy devices. However, before it can be part of such networks, the crystal-free SCµM chip needs to be able to accurately tune its communication frequency to synchronize to the network. This is a challenge since its on-board RC and LC-based resonating circuits have a drift rate that can be 3 orders of magnitude worse than crystal-based oscillators typically used in today's radios. This article introduces QuickCal, a solution that allows a SCµM chip to self-calibrate against off-the-shelf devices dedicated to assisting with its calibration. We show that a SCµM chip can self-calibrate against this QuickCal Box in fewer than 3 min. We further validate that, once it has self-calibrated, a SCµM chip can reliably communicate with off-the-shelf IEEE802.15.4 devices. Finally, we demonstrate a heterogeneous network-composed of a SCµM chip and an OpenMote device-implementing a full 6TiSCH Industrial IoT protocol stack, which uses time synchronization and channel hopping. This is the first time that a crystal-free radio is participating in a channel-hopping enabled TSCH network.

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