Cisco 6921

I hope you can help me with this. I have several cisco devices 6921. I achieved to make the conversion to SIP using TFTP server, try to charge the files SEP (MAC). Cnf.xml with the settings to work with SIP according says in a document, but I can not get the phone asterisk recognize me as an extension. Anyone know what are the exact steps for this device to work on my asterisk?

Just wondering if you ever got the correct config files to work? I am having a lot of trouble.