CircleOS is an embedded OS running on the STM32 Primer development kits. For further information go to http://www.stm32circle.com/ .
This is a port of Contiki OS version 2.2.1, running as an applicationon top of Circle OS. It is possible to create multitasking applications in Contiki OS. This port of Contiki OS also has uIP, the TCP/IP stack, ready. Upon serial-over-USB connection a SLIP layer is started. The address of the Primer is 192.168.3.2 with netmask 255.255.255.0 . It is possible to ping the Primer if you make payload of the ping packet less than 24 bytes.
The problem lies in the USB FIFO of 64 bytes only, which is not really sufficient. One could try to enlarge the calling frequency of the serial handler of Contiki, so that the serial FIFO is processed faster. If this workaround will succeed, entire VNC based desktop of Contiki OS could be ported, making it possible to run web browser or even Twitter client. Porting this project to Primer 2 would make it possible to use filesystem interface of Contiki to read contents of SD card, making Primer 2 a very nice portable webserver.
Downloadable as Contiki-2.2.1-on-CircleOS-1.7.zip .