ESP32 & RP2040 Based Capacitive Touch Audio PCB Project

In this project, two different PCB designs with similar features but different microcontroller platforms were developed. The boards are based on ESP32 and Raspberry Pi RP2040 and include 12 and 14 capacitive touch inputs. Audio files assigned to each touch pin are played directly from an SD card with high sound quality.

Project Purpose

The main goal of the project is to play audio files assigned to capacitive touch pins by reading them from an SD card and outputting clean, low-latency sound using dedicated audio components. The system is designed for educational tools, accessibility devices, and interactive applications.

                                                     RP2040 PCB BOARD DESIGN

                                                    ESP32 PCB BOARD DESIGN

Capacitive Touch Interface – MPR121QR2

Capacitive touch sensing is handled by the MPR121QR2 touch controller.

-12 independent capacitive touch channels

-High sensitivity and stable touch detection

-I²C communication with the microcontroller

-Touch electrodes can be extended via cables

-Adjustable thresholds and noise filtering

This allows flexible placement of touch surfaces away from the main PCB.

Audio Output – PCM5102APWR

High-quality audio output is achieved using the PCM5102APWR DAC.

-I2S digital audio interface

-24-bit resolution, up to 384 kHz sampling rate

-Low noise and low distortion

-Clean output for external amplifiers or speakers

Power Management – TLV75733PDBVR

For efficient and stable power delivery, the TLV75733PDBVR low-dropout regulator is used.

-Fixed 3.3V output

-Low dropout voltage

-Low quiescent current

-Suitable for sensitive analog and digital circuits

PCB and Hardware Features

-4-layer PCB design

-ESP32 and RP2040 board variants

-MPR121QR2 capacitive touch controller

-PCM5102APWR high-quality DAC

-SD card-based audio playback

-USB Type-C power input

-Low-power LDO regulation

-Cable-extendable touch inputs

Conclusion

This project combines flexible capacitive touch input, SD card audio playback, and high-quality sound output into a compact and scalable hardware platform suitable for both educational and commercial products.