8.2.3 Five Stages of OTAU Procedure

  1. Discover device supported feature – In this step, the OTAU client enquires the image types supported by the server. The OTAU client sends a read request to the server and the server will notify the client in response.
  2. Claim to execute firmware update – The OTAU client issues the firmware update request operations using the OTAU control point characteristics and, for the no error conditions, the OTAU server allows the firmware update procedure. The package content from the client contains the size of the new firmware image, identity of the new firmware image, the version of new firmware image and the new firmware image encrypt method.

    The OTAU server, then, responds with the result code, the maximum fragmented image size, the start index of the image and the version of the current firmware image.

  3. Start firmware update – The OTAU client issues the firmware update start operation and for the no error condition, the OTAU server starts the firmware update procedure. The OTAU client sends the image type, and the server responds with a result code. The server, then, updates the process.
  4. Firmware distribution – The OTAU client initiates to send the fragmented image to the OTAU server. When the total length of received fragment reaches the Max Fragmented image size, the OTAU server decrypts the image and starts to write to the Flash. After the write operation to Flash, the server verifies the written content.
  5. Firmware updates complete – The OTAU client informs the OTAU server after the completion of the firmware update process. The OTAU client issues a device reset request to the OTAU server, and the server a software reset.