This project using Arduino Nano and CMX860 (CML Micro), communicate through SPI interface.
Generate DTMFcommand send from HOST (PC), and detected DTMF reported to Host (PC), through serial port.
For your reference, please check my attachment (CMX860 datasheet, and sample source code)
Sory, I mean Arduino UNO (Nano not have SPI, right?)
Or... if you don't need Arduino, you can using MCP2210 (Microchip USB - SPI), but if using MCP2210, it's mean you can write code using C# or VB (in host side). Thanks