@startuml
skinparam BackgroundColor F0F0F0
start
:User checks firmware version;
:Read current version;
note right
    Read from modem with AT+QGMR
end note
:Download versions file from server;
note right
    Simple file format:
    <current versions>:<new version>:<delta file>
end note
:parse file;
note right
    based on current version, get <delta file>
end note
if (user allows update) then (yes)
    :Download & install new firmware;
    note right
        use command
        AT+QFOTADL=<httpURL>
    end note
endif
:reboot device;
stop
@enduml