I was trying to configure an ADAU1701 connected to a raspberry pi (over an i2c bus, running Raspbian) using SigmaTcp. Unfortunately, I was unable to do that in the first attempt. I analyzed the TCPIP packages sent by SigmaStudio using wireshark and I noticed that the header was different from the one that SigmaTcp was waiting. Sigma tcp waits for a 8 bytes header, with length in the bytes 4 and 5, and addr in the bytes 6 and 7. SigmaStudio sends a 10 bytes header with length in the bytes 6 and 7, and addr in the bytes 8 and 9. After some changes in function handle_connection on sigma-tcp.c, I was able to control the chip over a TCP/IP connection.
Is there a different version of sigma tcp to be used with ADAU1701? I searched in this forum and couldn't find anyone with the same problem, so I decided to post this.