# Cacao - Multi-Channel Signal Acquisition Board

Cacao is a compact 12-channel audio-frequency signal-acquisition board built around the RP2350. It explores how modern, accessible components can consolidate multi-channel acquisition, buffering, storage, and Ethernet communication onto a single 80 x 50 mm PCB.

![Cacao PCB - 3D render](figures/Recto.png)
![Cacao PCB - 3D render](figures/Verso.png)

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## Overview

Cacao was developed independently as a proof of concept alongside an industrial R&D internship. The project acts as a technical calling card: a complete architecture, schematic, and dense PCB layout designed to demonstrate what can be achieved with a modern microcontroller and cost-effective audio-conversion hardware.

Twelve differential audio inputs are digitized by three TLV320ADC5140 ADCs at 44.1 kHz. The RP2350 collects and processes the resulting data before sending it over 100BASE-TX Ethernet through a W5500 or storing it locally on a microSD card.

## Key Features

- RP2350 in the 80-pin package with internal flash
- 12 differential audio-input channels
- Three TLV320ADC5140 four-channel ADCs synchronized by a 2.5 ppm clock
- 44.1 kHz acquisition with planned 12- or 16-bit sample handling
- W5500-based 100BASE-TX Ethernet output
- 8 MB external RAM for acquisition buffering
- MicroSD storage for standalone data capture
- USB-C 5 V power input
- 3.3 V buck supply for the digital electronics
- Separate low-noise 3.3 V analog rail using an LP5907MFX-3.3/NOPB LDO
- Four-layer, 80 x 50 mm PCB with more than 200 components
- Components on both sides, with most passive components placed on the back

The Micro-USB connectors are used as compact keyed connectors for the differential analog channels and their 5 V amplifier supply. They are **not USB data ports**.

## Engineering Focus

The principal layout challenge was integrating 12 analog channels, three synchronized ADCs, local buffering, storage, Ethernet, and the required power architecture within an 80 x 50 mm footprint. Particular attention was given to separating low-noise analog supplies from the general digital rail, maintaining clean reference and return paths, and placing a large number of passive components without increasing the board area.

An alternative future configuration could replace the W5500 and external RAM with a W6300 connected through QSPI, reducing the number of separate devices while retaining high-speed Ethernet communication.

The firmware will have to be as efficient as possible to allow 10-12 channels at the same time to be sampled and transferred to the W5500.

## Project Status

V1.0 is currently in production at Aisler.com and will be assembled by myself