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Weekly Report - 15/08/14




I've just finished up and run through my presentation this past week, ready to give (twice) on Wednesday. Wrote myself a script which I will need to stick to relatively closely in order to keep within 15 minutes. Should be good fun.

I started looking into running a CoAP application and found (as I had suspected earlier) that the CoAP example included with the 6lbr-demo application won't compile out of the box for my platform - it overflows the RAM by about 500 bytes, which is rather annoying.

I was hoping to find that I had just overlooked something related to compiling for low-resource devices, such as the Zolertia Z1, which also has only 8KB of RAM and is supported (there is a testbed subroutine in the Makefile which compiles the CoAP server for the Z1, although I haven't tested this due to not having the compiler installed for that platform). I did discover that the Z1 only has a 16-bit MCU while the STM32W is 32-bit, and I wondered whether that would have made any difference, but I talked that over with Richard S and we came to the conclusion that it probably couldn't have made as much difference as we were seeing.

Richard suggested trying some compiler flags and we found one of them which managed to reduce the overflow to only ~240 bytes. Contiki is already fairly heavily optimised however, so the other flags we tried weren't any use. It's possible that from here I could make some adjustments to buffer lengths etc, which might be an acceptable compromise at least to get things working.