8.1 Introduction

This section describes the detailed procedure of updating the device firmware on the RNBD451 module. New firmware can add Bluetooth Low Energy-specific functionality for new revisions of the Bluetooth specification, as well as provide a way to fix bugs discovered in the current device's Bluetooth operation.

Microchip periodically releases new firmware for the RNBD451 device and it is always recommended to update the device with the latest version of firmware. Microchip distributes the intended firmware files via the official webpage of the RNBD451. The format of the distributed firmware files is .bin.

The command set support available in the RNBD451 module put forward the opportunity to update the device firmware in the RNBD451 in two possible ways. Each feature is intelligently designed and implemented to meet the application requirement.

  1. OTA firmware update – The OTA is a protocol that allows Bluetooth Low Energy devices to receive a firmware image OTA from another Bluetooth Low Energy device. The Microchip-defined OTA profile and service enables firmware upgrades over the Bluetooth Low Energy link using Generic Attribute Profile (GATT). The Bluetooth Low Energy OTA protocol defines the communication between the OTAU target and the OTAU manager. The OTAU manager can be a mobile device (iOS/Android™) or any Bluetooth Low Energy device that implements the OTA GATT client protocol that transfers the upgrade firmware to the OTAU target. The OTAU target implements the OTA GATT server protocol to receive the new firmware image.

    This approach strictly recommends having a successful and secure Bluetooth Low Energy link connection between two devices.

    1. OTA from mobile application – The mobile application is the OTAU manager that holds the new upgradable image and sends it to the RNBD451 device over the Bluetooth Low Energy link.

    2. OTA using another RNBD451 device – This method implements the device firmware update on a remote RNBD451 device with the help of a peer RNBD451 device. The RNBD451 that acts as the OTAU manager in the central role supports a special Over-the-Air Profile in Client Role (OTAPC).

      With the help of OTAPC command set support, the central device is configured to work in DFU mode and carry out the OTAPC commands. For more information about the DFU commands, refer to the 5.7.3.1 OTAPC Commands.

  2. Serial Device Firmware Update (Serial DFU) – In this method, the firmware update on the RNBD451 device is achieved via serial UART communication. The RNBD451 command set supports the DFU commands to carry out serial DFU. To make use of the DFU update feature, first configure the device in the DFU mode. This method is very similar to the direct firmware update procedure using a wired connection. In practice, the DFU commands are invoked in a specific order to successfully update the firmware. For more information about the DFU commands, refer to the 5.7 DFU Commands.