[XCSSA] Attempting to hack a ip8100 (Cordless SIP phone)

[X-otic Computer Systems of San Antonio]

Hey,

Maybe with all the hardware hackers on here, someone can help me out.

I acquired a Vtech ip8100 voip phone thingy that's currently locked to 
vonage. From what I've read on the internet, if I can downgrade the 
firmware, I can use a tool called CYT tool to reset the passwords and 
then provision it however I'd like to.

Unfortunately, I'm not able to do any of the hacks, and simply sending 
it a firmware isn't working. It won't take the downgrade.

I've cracked open the box and found console pins on there, but I need a 
serial port to TTL converter module:
http://cgi.ebay.com/RS232-Serial-Port-To-TTL-Converter-Module-MAX3232-LED_W0QQitemZ300249101371QQcmdZViewItem

I was wondering if perhaps someone had one of those I could borrow, or 
would maybe like to help me get this working? I've got a few firmwares 
for it, just need to get them on there. I should theoretically then be 
able to unlock it and have myself a pair of cordless SIP phones :D

Thanks,

David