Firstly you need to find out if u'r fone is AT-capable most of valid fones have modem dlr3p cable will only work in 6110 series and 7110 series or compatible phones i believe 6100 is using POP-PORT and if u'r talking about USB connection either HOST or PERIPEHERAL mode you will be needing USB to TTL logic converter like those chips from maxim or FTDI because USB is LVDS "low voltage differential signaling" try to find out more about your phones POP-PORT if it sends out TTL and if it is AT-commands compatible and by the way you need to figure out if your phone is can handle TEXT or is PDU by defualt the formeris easier!!! if it is in PDU mode you wont be able to get a response from your phone you will need to be doing translation in your software!!!

PS.

The 7-pin in the ckt is directly pin to pin to 6110 or 7110 port i used an old headfone very cheap even the fone is cheap roughly 900 pesos or 20US$

Yours Trully Ryan