Anyone who has built the software side of a connected product knows the glue job. The device keeps its readings in one format and the gateway wants rows in a SQL database, so somebody writes a converter. Then somebody has to keep that converter alive for as long as the device stays in the field, which can easily be ten years.

AltSql takes the converter out. Its base engine, AltSql Core, compiles to about 15 KB of code for a microcontroller. The device keeps its readings and settings in its own flash and goes on deciding from its own data when the connection goes. Its gateway stores the very same records, byte for byte, and answers SQL over them.

The progress bar is the least informative part of a firmware update. It moves at a rate that has almost nothing to do with the work being done, it frequently sits at the same percentage for two minutes, and the warning attached to it says not to power off the device without ever explaining what would break if you did. Here is what the sequence actually consists of, and where it can go wrong.