Technical information

Chapter 2: AT+i Commands Reference
May 31, 2008 AT+i Commands Reference Manual 2-71
Remote Firmware Update
Introduction
W24 accepts remote firmware updates from an HTTP or FTP server. The firmware update is
stored as an .imz file on the host server and downloaded by W24 acting as a client. W24 replaces
its existing firmware with the new one through a special application that is part of the .imz file.
This method is especially convenient when managing firmware updates in a globally distributed
install base of internet-enabled devices.
Updating Firmware from a Remote Server
This method involves placing the firmware update .imz file on an HTTP or FTP server. W24 has
the provisions to use its respective HTTP or FTP client to download the firmware update file and
perform the update process.
Before the actual remote firmware update command can be issued, the following parameters must
be set:
• USRV - Defines the protocol to be used (HTTP or FTP), and the name of the host on which
one or more .imz files are stored.
• UUSR - Defines FTP user name (FTP only).
• UPWD - Defines FTP user password (FTP only).
• UEN - This flag indicates whether W24 updates to a firmware version that is newer than the
currently installed one only, or to any firmware version it finds.
In addition, an appropriate .imz firmware update file must be placed on the remote server at the
location specified by the USRV parameter.
Once the above parameters are defined, the firmware update process can be initiated by sending
the following command to W24:
AT+iRFU
W24 returns I/OK to acknowledge receipt of the command. As the update process may take up to
4 minutes to complete, W24 issues an I/UPDATE message to notify the host that it is in the
process of updating its firmware. The host must allow for an extended delay period until W24
completes the process. Once completed, W24 re-boots the new firmware and issues an I/DONE
message when in dialup mode, or an I/ONLINE in WLAN mode.
Several safeguards have been instated to ensure a successful firmware update. The firmware
update file is structured in a specific format, which allows W24 to authenticate its origin as a
legal firmware image. W24 also verifies that the firmware update is the correct version for its
hardware environment. W24 rejects an update file if it contains an image that is identical to the
one already installed.
The remote firmware update procedure is detailed below:
1. W24 downloads the new firmware imz file.
2. If the download fails, W24 returns an error message and continues to work as before.
3. If during the download W24 is going over a reset cycle (SW or HW), W24 re-boots and
executes the old firmware.
4. If the download is successful, W24 authenticates the firmware image file.