Appendix: Delta update campaigns

To update a deployed device's firmware, you can use a delta update campaign instead of a full update campaign.

A delta patch contains the information necessary to reconstruct the new image from the old one. This means you only need to transmit the delta, not a full new image, to the device. Delta updates can save bandwidth and energy for NarrowBand-Internet of Things (NB-IoT) devices, or when installing large firmware images with only small code changes. Using a delta image can also reduce the amount of time needed for an update campaign.

Running delta update campaigns is mostly similar to running full update campaigns. The main change is that you need to generate and upload a delta patch and not the firmware image.

1. Generate a delta patch

1. Save the image currently installed on the device, BUILD/<target>/<toolchain>/mbed-cloud-client-example_update.bin.

2. Build the new firmware image.

3. Use manifest-delta-tool to generate the delta patch file:

   manifest-delta-tool --current-fw <current image> --new-fw <new image> --output delta-patch.bin
   

   Where:

   • <current image> is the path to the currently installed firmware image.
   • <new image> is the path to the candidate image.

2. Upload the delta patch to Device Management Portal

Upload the delta-patch.bin patch file to Device Management instead of a firmware image, as described in Upload the image to Device Management Portal.

3. Update your manifest configuration file

When you prepare your manifest configuration file, set:

• Payload format arm-patch-stream instead of raw-binary.
• file-path to the local path of the delta-patch.bin file.

4. Continue to create manifest and campaign

Continue to create a manifest and campaign, as described in Update your device's firmware image.