A “bundle” file has a custom format, designed to minimise the code overhead of supporting the bundle on the target platform.
Note: An advantage of a custom binary format over, for example, the use of a tar-file, is that the binary image held on an SD card for update delivery would be IDENTICAL to the version installed in the target's SPI flash.
With the tar-file format there is an overhead associated with individual entries (e.g. 512-byte header, per-item padding) that would mean for (the limited space) target SPI flash storage the processing code would need to extract the individual items for efficient storage in the SPI flash. This process can be avoided by a simple binary structure that is copied unchanged.
A host-based command-line tool is provided to create a correctly formatted bundle binary image. The binary image can then be used in manufacturing and in-field update processes to distribute the main target application and all associated target data.