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The over-the-air (OTA) technology enables downloading a latest software release to a device and enables the device to automatically check and update firmware through wireless transmission. OTA allows users to quickly fix defects, provides a rich set of functions, and shortens the cycle of product iteration and update.

This document introduces how to update GR551x firmware through GRToolbox (Android) by using Bluetooth Low Energy (Bluetooth LE) technology. Two update approaches are available. Users can choose an appropriate one based on product requirements:

  • Jump to Boot firmware for firmware update. During firmware update, the system jumps from applications to the Boot firmware, and the Boot firmware enables download of the target firmware. After download, the system jumps to the target firmware for running. During update, it is required to first disable Bluetooth connection on the mobile phone and then scan and reconnect to the Boot firmware via Bluetooth. Compared with the second approach, this approach makes the best use of flash.
  • Perform update in application firmware (for example, ble_app_template_dfu). Run the application firmware to download the target firmware. After download, the system jumps to the target firmware for running. During update, users can update firmware directly without disabling Bluetooth connection on a mobile phone. This approach provides smooth user experience.

Before getting started, you can refer to the documents in Table 1.

Table 1 Reference documents
Name Description

GR551x Developer Guide

Introduces GR551x Software Development Kit (SDK) and how to develop and debug applications based on the SDK.

Bluetooth Core Spec

Offers official Bluetooth standards and core specification from Bluetooth SIG.

J-Link/J-Trace User Guide

Provides J-Link operational instructions. Available at www.segger.com/downloads/jlink/UM08001_JLink.pdf.

Keil User Guide

Offers detailed Keil operational instructions. Available at www.keil.com/support/man/docs/uv4/.

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