Upgrade from SDK 2.4.1 to SDK 3.x,
The bootloader also have to be upgrade too!
Did you already released a product with SDK-2.4.1 release and trying to OTA with SDK-3.x?
If not, please migrate your application to SDK-3.x and use the OTA support from new release. There had been major changes to OTA on SDK-3.x.
Regarding to OTA sample app there is a blog post you can take a look at, WICED OTA Upgrade and Factory Reset (SDK 3.1.2 through WICED Studio 4.x)
Unfortunately we have previously released some sample products on the top of SDK-2.4.1. Via OTA, we must upgrade our previous products' SW (based on the sdk 2.4.1) to our new SW on the top of SDK-3.x. We are aware of the sad fact that the bootloader has to be upgraded to upgrade from SDK 2.4.1 to SDK 3.X.
We have already migrated our application to SDK-3.x. We can successfully use OTA-upgrade between two applications which both are based on SDK-3.x.
However, open question is still that: how can we ota-upgrade our previous products(SDK 2.4.1) to the SDK-3.x? Do you have any sample application to upgrade both bootloader and app?
Unfortunately there is no easy way to upgrade released product from SDK-2.4.x to SDK-3.x.
We are working on a new version of SDK-2.x that backports most of the fixes were done on 3.x and provide an upgrade path for released 2.4.x devices. There is no date for the release of the backported SDK-2.x.
One option is loading the OTA application to a memory location that would be outside of the bootloader, DCT and app using SDK-2.4.1. First step is to upgrade the existing 2.4.1 version with relocated OTA application using SDK 2.4.1. Newly located SDK-2.4.1 release of OTA upgrades the bootloader, DCT and app built by the SDK-3.x. This two steps upgrade would be very cumbersome. If you have a limited test release of devices, perhaps re-flashing the devices would be the easiest upgrade method. There is no snippet application sample code for the above example.