Hi! I'm developer of Embox project (http://embox.github.io/) Our team managed to run pjsip on stm32f4 discovery board with 160mhz/192KB RAM/1MB FLASH. We've used usual desktop configuration, sound is produced via portaudio api. pjsua was to big in RAM requirements, so we took simpleua, compiled it with -Os. Even so, most efforts was spent on minimizing heap consumption, in order to do it we had to disable pool policies with #define PJ_POOL_DEBUG 1 Even after, simpleua used 58000 + 65000 bytes of heap, distributed in 2 RAM banks, along with ~8000 bytes (main thread) + 3000 (portaudio thread) of stack, and ~30kb bytes of static memory. Another 2kb's was used as network buffers, and 10 kb's as audio buffers. We've made a small demo http://www.youtube.com/watch?v=y2Eg_zwuI7M To build discovery image, embox repo should be configured and built like make confload-platform/pjsip/stm32f4discovery && make (pjsip will be downloaded and installed) Host companion tools are on https://github.com/embox/pjsip Thank you for software, guys! Best regards, Anton Kozlov