One idea I have had is to create a set of gCore shields which like various Arduino shields and Pi Hats add hardware functionality for specific applications.  The first board is called the gCore POTS shield and was designed to let me re-imagine the BluePOT project in a more general purpose project called weeBell.

(gCore POTS shield)

The gCore POTS shield connects to gCore's IO Expansion header and contains a codec chip and the Silvertel AG1171 Ringing Subscriber Line Interface module.  These two devices allow creation of a full Foreign Exchange Service (FXS) device which simulates a central office.  Old school POTS telephones plug into the RJ11 jack.  Firmware running on gCore implements functionality necessary to ring the phone for incoming calls, detect on- and off-hook conditions, support both rotary and DTMF dialing and provide echo-cancelled audio.

(Rotary Dialing)

Currently firmware called weeBell_bluetooth allows phone calls to be answered or initiated via a paired cellphone.  I hope to create other firmwares as well.  All firmware will be included as part of the gCore Serial Programmer library making it easy to load new versions.

(Loading weeBell firmware)