LoRa IoT Device Firmware Update through Cloud Over-the-Air Interfaces
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LoRa IoT Device Firmware Update through Cloud Over-the-Air Interfaces
Projects

LoRa IoT Device Firmware Update through Cloud Over-the-Air Interfaces

LoRa IoT Device Firmware Update through Cloud Over-the-Air Interfaces

Firmware is an integral part of devices, which refers to the software that instructs the hardware to function and commu- nicate with other software running on a device. Firmware updates are necessary to address security or performance issues during the lifetime of IoT (Internet of Things) devices. Over-the-Air (OTA) updates enable firmware updates to be completed remotely and securely, without the need to re- move devices from their deployment.

This paper introduces a LoRa (Long Range) OTA procedure to enable cloud-based resources to initiate and complete updates to LoRa-connected IoT devices. This differs from existing OTA over LoRa solutions by allowing the LoRa gateway to simply push updates from upstream servers man- aging the deployment of devices. Upstream servers expose APIs to allow devices communicating over a TTS instance to initiate the OTA procedure. A PyCom FiPy was chosen as the IoT device on which to perform OTA.

Paper

Background

  • LoRa is a long-range, low-power networking protocol that allows IoT devices to communicate securely. It allows devices to be managed by base stations while allowing them to function for years without depleting on-board batteries.
  • Over-the-Air (OTA) updates have enabled security patches and mission-critical updates to be delivered to increasingly important IoT devices.
  • As part of managing these devices, it makes sense to be able to carry out OTA updates over LoRa.
  • Our Goal: Enable LoRa OTA between Cloud and LoRa Devices.

Procedure:

  1. Device connects with server over WiFi
  2. Device requests manifest
  3. Server sends builds & sends manifest
  4. Device receives manifest and updates application and firmware files accordingly
    1. Requests files that are not on device from server
    2. Backs up old files that needs to be updated
    3. Deletes obsolete files per manifest directives
  5. For every firmware file, write firmware to OTA partition on device and set flag to boot from OTA instead of partition
  6. Machine resets to complete update

Implementation Steps

Setup Configurations

LoRa Socket:

  • LoRaWAN Mode – US-compliant bandwidth, channels, and frequencies (Zone: US915)
  • LoRa OTAA (Over the Air Authentication)
  • Blocking set – device waits for packets to be received
  • Socket timeout set to 15 seconds – client triggers retransmission after 15 seconds of not receiving an expected packet

Triggers/ACKs/NACKs:

  • No OTA protocol for LoRa: start, stop, data format etc.
    • Example WiFi OTA code only send arbitrary bytes as trigger – we do the same thing
    • Using arbitrary bytes
  • LoRa also does not have ACKs – we set our own bytestring to ACK
    • After server receives ACK, disposes of the last binary chunk / the last packet sent
  • LoRa also does not have NACKs – we set another bytestring to serve as NACK
    • After server receives NACK, retransmits the last binary chunk / the last packet sent
    • Use of NACK is not ideal, but it works very well! Retransmission is guaranteed in case of packet drop/transmission failure

Data Segmentation:

  • Data segmentation of the binary is done on the server
  • Our current chunk size is 40 bytes

Achieved:

  • Transfer of files from webserver to LoRa device
  • Concatenation of chunks on end device to a file
  • Writing of files into OTA (firmware) partition
  • Retransmission of the last message from the server to the device if the device times out

Demo