This board serves as a carrier for the DFPlayer, providing stable power, protection, and convenient interfaces for audio input and output. It is designed to be easily integrated into larger audio projects.

Features

Power Supply: On-board diode is used to drop the input voltage to a DFPlayer-safe ~4.3V. An electrolytic capacitor is included for power supply filtering, ensuring smooth operation.
All SMD Components: Designed for a low-profile, surface-mount assembly, making it suitable for compact enclosures.
Simple Interfaces: Utilizes standard JST and 3.5mm connectors for power, data input, speaker output, and stereo line-level output.
Compact Design: A small footprint carrier board for the 2x8 pin DFPlayer Mini module.

Interfaces

Input

Connector: 4-pin JST PH 2.0mm
Signals:
- +5V: Power input
- GND: Ground
- TX: Serial Transmit (connects to DFPlayer RX) protected by the 1kΩ resistor
- RX: Serial Receive (connects to DFPlayer TX)
Description: This interface provides both power and UART serial communication to the DFPlayer module. It is important to note that the DFPlayer's RX pin is not 5V tolerant, so a 1kΩ series resistor is included on the board for protection.

Outputs

1. Speaker (Mono)

Connector: 2-pin JST PH 2.0mm
Signals:
- SPK+
- SPK-
Description: A direct, amplified mono output for a small speaker (up to 3W). This connects directly to the SPK1 and SPK2 pins of the DFPlayer.

2. Stereo Line Out

Connector: 3.5mm Stereo Audio Jack (SMD)
Signals:
- L: Left Audio Channel
- R: Right Audio Channel
- GND: Ground
Description: A line-level stereo output suitable for headphones, external amplifiers, or other audio equipment. This connects to the DAC_R, DAC_L, and GND pins of the DFPlayer.

Power Supply Circuit

The motherboard is designed to be powered by a standard +5V source. To ensure the DFPlayer module receives a safe operating voltage (typically 3.2V to 5.0V, with 4.2V being ideal), the following components are included:

Voltage Drop Diode: A standard silicon diode (e.g., a 1N4001 SMD equivalent) is placed in series with the power input. This provides a forward voltage drop of approximately 0.7V, effectively reducing the 5V input to a safer ~4.3V for the DFPlayer.
Filtering Capacitor: An electrolytic capacitor (e.g., 470µF, 10V) is placed across the DFPlayer's power pins (VCC and GND). This smooths the power supply and filters out noise, which is crucial for clean audio playback.

Mechanical Design

Mounting Holes: The board includes four mounting holes, one in each corner.
Hole Diameter: 3.2mm, providing clearance for standard M3 screws.
Compatibility: Designed for use with M3 nylon or brass standoffs for easy mounting.

Bill of Materials

Component	Qty	KiCad footprint	LCSC Part #
Female 8-Pin Header	2	PinSocket_1x08_P2.54mm_Vertical_SMD_Pin1Left	C48641756
Diode	1	D_SMA	C18199093
Electrolytic Capacitor	1	EEEFK1A471AP (470µF/10V), for power filtering	C178529
UART Connector	1	JST_PH_B4B-PH-SM4-TB_1x04-1MP_P2.00mm_Vertical	C160354
Speaker Connector	1	JST_PH_B2B-PH-SM4-TB_1x02-1MP_P2.00mm_Vertical	C265003
Audio Jack	1	Jack_3.5mm_PJ320D_Horizontal	C22459515
Resistor	1	1kΩ, 0805 SMD (for UART RX line)	C17513

Assembly

This project is intended to be built with surface-mount components. A soldering iron with a fine tip, solder paste, and a hot air rework station are the recommended tools for a clean assembly.

How to Use

Prepare an SD Card: Format a microSD card (up to 32GB) to FAT16 or FAT32. Copy your MP3 or WAV files onto the card.
Insert SD Card: Place the microSD card into the DFPlayer module's slot.
Connect DFPlayer: Carefully plug the DFPlayer Mini module into the female socket headers on the motherboard. Ensure the orientation is correct.
Connect Interfaces:
- Plug in your +5V power source and UART controller (like an Arduino or FTDI adapter) to the 4-pin JST connector.
- Connect a speaker (e.g., 8Ω, 1W) to the 2-pin JST connector.
- (Optional) Connect headphones or an amplifier to the 3.5mm audio jack.
Power On: Apply power to the board and begin sending serial commands to control the DFPlayer.