Can you elaborate more on your first query? Do you want to understand how the OTA image upgradation happens or the query is related to the MQTT topic which is used to upgrade the firmware of the prototyping kit?
thanks for your response.
Actually to make the question more simple:
I want to have two OTA targets on the prototypingKit. One is the image for prototypingKit itself. Another one is the image for another subsystem hooked on prototypingKit by UART. I want to have the possibility of upgrade both of them. But from the callback function, I can't tell which system the downloading image is going to upgrade.
Currently I am doing something not nice work-around. Is there any suggestions, or existed solution?