Hi
I need to connect a Sony Ericson K810i Phone to Microcontroller(PIC16F876) as a GSM modem. Can anyone tell me how to connect this ??

 

I'm pretty sure you're gonna have to contact Ericson's technicial department or website to do that. Dont think the protocols are publicly well known since this is a quite not so comon project i would think :/

 

I don't know about K810i. It is quite modern phone with USB connection. From hardware point of view, it is already difficult to connect a PIC18F to an USB device (it has to act as a USB host). Not to mention the difficulty with unknown protocol.

The easiest way is to get old Ericsson or Nokia phones that supports serial interface. Then you can connect the phone to microcontroller and control it using AT commands (some variations on the AT comands depending on the phone used).