DTMF Receiver / PIC12F675

I know this has been gone over a million times, but I need a hand with this as its my first PIC project. Patience is appreciated.

I understand the usual DTMF receiver is the 8870 with 4 line parallel output. Digikey shows this as obsolete and shows a BU8872 which is non stock but available. Appears to be new technology, pins are reduced to 8 and output is serial one pin with an ACK pin and Steering "ESt" for handshaking.

My goal is to use the output from the headset jack on a cell phone, correctly attenuate the signal for audio input (automatically for any volume or cellphone?). I want a 4 digit code in the PIC with # to confirm / switch a MOSFET or possibly two channels depending on the code input. Provision to change the code by DTMF would be nice too. Writing the program will be the absolute hardest for me.

Is there a way to have a PIC output a beep and simply amplify it, route it back through the headset to have confirmation beeps for code input/change/MOSFET state?

I'm sure everyone can guess the application. I can assure you it is for private educational testing only.

If anyone wants to give me some dedicated education/spoon feed, we can talk about a bump in their PayPal account.

Thanks

Wow, you guys are really helpful. I appreciate it!

Most peoples first PIC project is often something basic like lighting an LED. Your project is somewhat more complex.

Start by posting your schematic.

Here is what I whipped up. Took me a while how to figure out drawing a new library device.
**broken link removed**

I wish to use the PIC to produce beeps back through the audio input. I don't know what it needs in between but I assume it doesn't need to be amplified because the phone takes care of that. As for the audio input, I have no idea how much to attenuate the signal. Plus there is the problem of changing the volume on the phone. Ideas?

If someone could review this that would be great. Attached is the Eagle *.sch file; please rename accordingly. I will append the datasheet links.

Thanks

https://www.electro-tech-online.com/custompdfs/2009/03/41190c.pdf

http://www.datasheetcatalog.org/datasheet/rohm/bu8872.pdf