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The Second Boot example performs the functions of device firmware update (DFU), checking validity, jumping to, and running application firmware, as well as secure signature verification over Bluetooth Low Energy (Bluetooth LE) transmission and second boot of firmware, providing users with flexible, reliable, and secure Over-the-Air (OTA) functions.

  • Background dual-bank DFU by copying the firmware: Update the firmware by copying the firmware from one bank to another through OTA over Bluetooth LE transmission.
  • Checking validity, jumping to, and running application firmware: Compare the application firmware information with the information in APP Image Info. Jump to and run the application firmware (ble_tem_dfu_fw.bin is used as an example in this document) if the information from the two sources matches.
  • Secure verification: Sign the firmware to protect it against tampering and achieve non-repudiation. The Second Boot example verifies the signature before update.

Before getting started, you can refer to the following documents.

Table 1 Reference documents
Name Description

GR551x Developer Guide

Introduces the software/hardware and quick start guide of GR551x SoCs.

GR551x DFU Application Note

Introduces the principles and methods of Device Firmware Update for GR551x SoCs.

GR551x OTA Example Application

Introduces how to implement Over The Air for GR551x firmware on GRToolbox.

GProgrammer User Manual

Lists GProgrammer operational instructions, including downloading firmware to and encrypting firmware on GR551x SoCs.

GR55xx Firmware Encryption Application Note

Introduces how to encrypt data and firmware of GR55xx SoCs.

J-Link/J-Trace User Guide

Provides J-Link operational instructions. Available at

Keil User Guide

Offers detailed Keil operational instructions. Available at

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