Evolution of VESNA firmware size

11.06.2014 21:23

Yesterday I got an idea to plot how the size of the firmware images for VESNA sensor nodes evolved over time. Thanks to my diligent tagging of releases in git and making sure binaries can be built with a single make, all it took was a short bash script to come up with this:

Size of binary firmware image over time.

Only now do I realize that we've been polishing this code base for two years now.

When we originally started working on firmware that would run on spectrum sensing nodes in the Logatec testbed, a decision was made to develop everything from scratch and not go with an existing operating system like Contiki. The rationale was that we don't need all of its facilities and making something from scratch will be simpler than learning and building on existing work.

As it usually happens in such cases, over time we basically developed our own, small operating system. Given all the invested time, it is now hard to make a break from it, even when we have applications that would benefit from a standard platform like Contiki.

Looking at the graph, I'm actually surprised that the size of the firmware didn't increase more than it has. Keep in mind that these binary images are uploaded over a flaky ZigBit network where the best throughput is in the hundreds-of-bytes-per-second range. From the upload times to 50 nodes it certainly felt like it has increased a lot.

I didn't look into what features caused the most size increase. I'm pretty sure the recent large jump between versions 2.40 and 2.42 was because of a new SPI and microSD card driver. Also, one of the size decreases early on was after we added -ffunction-sections and -fdata-sections options to the GCC.

Posted by Tomaž | Categories: Code

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