Ambient audio capture and energy management daughterboard PCB

Audio capture and energy management daughterboard PCB for the Ambient project.

Main features

• Energy management:
  • Li-ion/LiPo charging circuit from photovoltaic cell with maximum power-point control (Consonance CN3791 controller),
  • solar and battery current and voltage monitoring (Texas Instrument INA3221 monitor),
• Audio capture:
  • analog-to-digital converter with microphone input amplification and digital filtering (Texas Instrument TLV320ADC3101),
  • analog audio wake-up circuit with high-pass filter and threshold detector.
• Magnetic reed switch for microcontroller reset

Project structure

• / (repository root): KiCad project and libraries
• pdf/: Schematics generated from the KiCad project
• png/: Screenshots of the KiCad 3D render
• production/: Gerbers, BOM and placement files generated from the KiCad project (compatible with JLCPCB manufacturing and assembly)
• webp/: Pictures of the actual board

Connectors and headers

J1: SOLAR

Solar cell power input.

Solar cell voltage range: 4.6 V to 20 V.

Pin	Net
1	SOLAR+
2	GND

J2: BATTERY

Li-ion or LiPo single-cell battery.

Minimum charging current rating: 800 mA.

Cell with built-in protection circuit required.

Pin	Net
1	BATT+
2	GND

J3: SYS

Power output to the mainboard.

Pin	Net
1	SYS+
2	GND

J10: MIC_RIGHT

Unused in the Ambient variant.

Right condenser electret microphone input.

Pin	Net
1	MIC_RIGHT
2	GNDA

J11: MIC_LEFT

Left condenser electret microphone input.

Pin	Net
1	MIC_LEFT
2	GNDA

J9

Connects to the mainboard PCB.

Pinout:

Pin	Net	Pin	Net
12	MCU_RESET	11	GND
10	EXT_MIC_IO_2	9	SAI_FS
8	EXT_MIC_IO_2	7	SAI_SD
6	I2C2_SCL	5	SAI_MCLK
4	I2C2_SDA	3	SAI_SCK
2	VDD_1V8	1	V_PERIPH_3V

Fabrication notes

PCB

Standard 2-layer 1.6mm stackup:

• 2 layers (front/back),
• 1.6mm thickness (not mandatory),
• 1oz copper,
• FR-4 dielectric,
• HASL finish.

No special requirements, any solder mask and silkscreen color.

Gerbers, BOM and position files are provided in the production/ directory but can be re-generated from the KiCad project using the Fabrication Toolkit plugin for JLCPCB.

Assembly

Recommended automated assembly for top-side only.

Manual assembly for bottom side:

• J3 and J9 connectors (through-hole).

Acknowledgment

This project has received funding from Université Côte d'Azur and CERN.