2.7 KiB
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.
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