Full-Duplex Radio System Design

flux

I can guide the design, but I’m currently unable to modify the Flux project directly because execution credits are unavailable. The project is still empty: 0 components and 0 nets.
Recommended architecture for two identical full-duplex stations:
  • Controller: Arduino Nano, 5 V logic
  • RF link: nRF24L01+ PA/LNA module at 3.3 V
  • Microphone: MAX4466 electret microphone preamp module, powered from 5 V or 3.3 V depending on the module
  • Speaker driver: PAM8403 class-D amplifier preferred over LM386 for better efficiency and volume from 5 V
  • Power: 5 V input for Arduino/audio amp, dedicated 3.3 V regulator for the nRF24L01+ PA/LNA
  • Audio output method: Arduino PWM pin with RC low-pass filter into the PAM8403 input
  • Audio input method: microphone output into an Arduino analog input
Important design note: true live full-duplex audio is demanding for an Arduino Nano. It has limited RAM, ADC speed, PWM quality, and processing headroom. It can work as a low-bitrate voice intercom with aggressive sampling/compression, but audio quality and latency will be limited. For better results, ESP32 or a dedicated audio codec/radio architecture would be stronger.
Suggested schematic connections:
nRF24L01+ PA/LNA to Arduino Nano:

Table

nRF24L01+ pinArduino Nano pinNotes
VCC3.3 V regulated railDo not power from Nano 3.3 V pin if using PA/LNA
GNDGNDCommon ground required
CED9Configurable GPIO
CSN / CSD10SPI chip select
SCKD13SPI clock
MOSID11SPI MOSI
MISOD12SPI MISO
IRQD2 optionalInterrupt input, optional
Power warning: many nRF24L01+ PA/LNA modules tolerate 5 V SPI logic, but the IC itself is 3.3 V. For a robust schematic, add logic level shifting or at least series resistors on Arduino-to-radio lines: SCK, MOSI, CE, CSN. MISO from radio to Nano is usually read correctly as HIGH at 3.3 V.
Microphone module:

Table

MAX4466 module pinArduino Nano
VCC5 V or 3.3 V per module rating
GNDGND
OUTA0
Audio amplifier:

Table

PAM8403 pinArduino Nano / power
VCC5 V
GNDGND
IN+ / L-INPWM audio after RC filter, e.g. D3
IN− / signal GNDGND or module input ground
Speaker outputsSpeaker only, do not connect to GND
PWM audio filter recommendation:
  • Arduino D3 PWM → 1 kΩ resistor → amplifier input
  • 10 nF capacitor from amplifier input to GND
  • Optional volume potentiometer between filter output and amp input
Decoupling capacitor placement:

Table

LocationCapacitorsPlacement
nRF24L01+ PA/LNA VCC-GND100 nF ceramic + 10 µF to 47 µF electrolytic/ceramicDirectly beside RF module power pins
3.3 V regulator inputPer regulator datasheet, commonly 1 µF to 10 µFClose to regulator input pin
3.3 V regulator outputPer regulator datasheet, commonly 1 µF to 10 µFClose to regulator output pin
Arduino 5 V rail100 nF + 10 µF bulkNear Nano 5 V/GND pins
PAM8403 VCC-GND100 nF ceramic + 470 µF bulk recommended for speaker current pulsesClose to amplifier module
Microphone VCC-GND100 nF ceramicClose to microphone module
Analog mic signalOptional 100 Ω series + small capacitor if noise is presentNear Arduino analog input
What remains to be done when execution is available:
  1. Rename the project from its draft name and create a short design specification.
  2. Select exact library parts/modules for Arduino Nano, nRF24L01+ PA/LNA, MAX4466 mic, PAM8403 amp, 3.3 V regulator, passives, and connectors.
  3. Check datasheets/module pinouts before wiring.
  4. Create the schematic with:
    • Arduino Nano block
    • RF transceiver block
    • Microphone input block
    • PWM audio output/filter block
    • Audio amplifier/speaker block
    • 5 V and regulated 3.3 V power block
  5. Add all decoupling and bulk capacitors.
  6. Verify ERC/power rails and confirm no unresolved schematic violations.
  7. Only after schematic verification, proceed to PCB placement and routing.
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