Micro-controller based Internet phone

This paper describes the development of a low cost micro-controller based, stand-alone Internet telephone to be used as an alternative to conventional line telephones. Bandwidth usage has been minimized to allow for use with dial up connections. The hardware comprises of a controller board for an AWC86 SlimLinkreg web server-controller (AWC86), which comes with a real-time operating system (RTOS) and TCP/IP stack, and codec boards for G.729 annex A (G.729A) codec ICs-MAS3159Fs. Cost was the main factor in the selection of hardware. Signalling is performed by the session initiation protocol (SIP) using the session description protocol (SDP) to negotiate the attributes of the media session to be established. The G.729A frames are transported between the units using the real-time transport protocol (RTP). RTP is accompanied by the RTP control protocol (RTCP). Two phone units were developed that communicated directly with each other and not through intermediary servers