A short tale of three firmware updaters. Device #1: A "root boot" loader in flash, very simple, loaded by a boot ROM. Its only job is to find the first good "l

A short tale of three firmware updaters. Device #1: A "root boot" loader in flash, very simple, loaded by a boot ROM. Its only job is to find the first good "large" chunk of boot code, get it into RAM and run it. The "large" chunks are in one of two slots. The update process is simple (update and test each slot independently), and if the update is interrupted there's always an image to boot from. It takes the developer responsible for FW update about a day to write the code and get it rock solid. An update takes less than about five seconds. Device #2: Implements a complicated file system. Some files need to be updated, some are untouchable, some need other special treatment (and the documentation is, unsurprisingly, dead wrong about things). The update process is very slow (tens of minutes) and if it is interrupted you wind up with a brick. It takes about two man-years to get the update process stable enough to ship. Device #3: Implements the standard USB firmware update protocol (DFU). There's a mountain of host-side code to deal with the edge conditions, and firmware updates are unpredictable. Devices get bricked pretty often. Takes maybe six months to get the update process stable enough to ship. Thinking of #2 and #3 still makes me mad. This stuff just isn't hard.