Low-Cost Interactive Voice Response (IVR) Device using Raspberry Pi for Automatic Calls and Messages

This interactive voice response system operates by interfacing a single-board computer with cellular network hardware to manage incoming and outgoing voice communication automatically. At the core of the power architecture, a 12V 2A adapter supplies the primary input voltage, which is stepped down by an LM2596 buck converter module to a regulated 4V necessary for the SIM800L GSM module. The Raspberry Pi communicates with the SIM800L module via a USB to TTL converter using serial communication protocols, issuing AT commands to initiate calls, hang up, and detect dual-tone multi-frequency (DTMF) tones generated by button presses on a telephone keypad. When a call is established or received, the Python environment runs a script utilizing the serial package to monitor communication states and the time package to manage delays. Audio playback is handled through an aux cable connecting the system to output pre-recorded audio messages generated via the pygame package. Together, these hardware and software layers allow the system to answer calls, navigate through user inputs, and deliver automated voice responses without manual intervention.