Files in the elf format can be uploaded. Today, most linkers generate elf format files so you don’t have to post process the linker output. The elf format can contain many different types of data, and only certain data will behave in a meaningful way when uploaded to target. µPad will warn you if it detects an elf file which is inappropriate for the target. However if such problems are detected it’ll go ahead and attempt to upload anyway.
Currently, µPad can only accept 32-bit elf files.