Overview

The RDA5807M (and variants RDA5807FP, RDA5807NN) is a single-chip CMOS stereo FM broadcast radio receiver IC manufactured by RDA Microelectronics. Sold as an ultra-compact 10-pin RRD-102 breakout module, it tunes FM radio frequencies from 50 MHz to 108 MHz (covering US, European, and Japanese FM broadcast bands).

Integrating a fully digital synthesizer, IF selectivity, digital automatic gain control (AGC), RDS/RBDS radio text demodulator, programmable bass boost, and internal $32.768\text{ kHz}$ clock driver, the RDA5807M outputs analog stereo audio capable of directly driving $32\ \Omega$ headphones or audio power amplifiers over an $I^2C$ bus. It is widely used in DIY FM radio receivers, alarm clocks, and retro boombox projects.

Quick reference

Pinout (RRD-102 Module 10-Pin Header)

        ┌───────────────────┐
        │  [RDA5807M IC]   │
        │  [32.768kHz XTAL] │
        └─┬─┬─┬─┬─┬─┬─┬─┬─┬─┘
          1 2 3 4 5 6 7 8 9 10

Specifications

$I^2C$ Register Access Modes

The RDA5807M supports two distinct $I^2C$ communication modes:

1. Direct Mode (0x11 Address): Allows reading and writing specific 16-bit registers (such as 0x02 for basic control, 0x03 for frequency channel tune, 0x05 for volume and bass boost).
2. Sequential Mode (0x10 Address): Backward compatible with the legacy TEA5767 FM chip. Writes start at Register 0x02 and automatically increment.

Frequency Calculation (Channel Register 0x03)

$\text{Frequency (MHz)} = \text{Bottom\_Freq} + \left( \text{CHAN} \times \text{Channel\_Space} \right)$

For standard US/European tuning ($\text{Bottom\_Freq} = 87.0\text{ MHz}$, $\text{Space} = 100\text{ kHz}$):

$\text{CHAN} = (\text{Target\_Freq\_MHz} - 87.0) \times 10$

Wiring

Example (Arduino Radio Library)

#include <Wire.h>
#include <radio.h>
#include <RDA5807M.h>

#define FIX_BAND RADIO_BAND_FM
#define FIX_STATION 10150 // 101.5 MHz FM

RDA5807M radio;

void setup() {
  Serial.begin(9600);
  Wire.begin();

  Serial.println("Initializing RDA5807M FM Radio...");
  
  if (!radio.initWire(Wire)) {
    Serial.println("RDA5807M not responding!");
    while(1);
  }

  radio.setBand(FIX_BAND);
  radio.setFrequency(FIX_STATION);
  radio.setVolume(10); // 0 to 15
  radio.setMono(false); // Enable Stereo
  radio.setBassBoost(true); // Enable Bass Boost

  Serial.print("Tuned to "); Serial.print(FIX_STATION / 100.0); Serial.println(" MHz FM");
}

void loop() {
  // Read RDS Radio Text if available
  char buffer[32];
  radio.formatFrequency(buffer, sizeof(buffer));
  delay(2000);
}

Common mistakes

• Connecting VCC to 5V: The maximum supply rating is 3.6V. Supplying 5V destroys the chip.
• Forgetting an antenna wire: Operating without an antenna wire on pin 10 results in heavy static noise and inability to lock onto FM stations. Connect a $75\text{ cm}$ (~30 inch) length of insulated copper wire.

Notes

• RDA5807 vs TEA5767 vs SI4703: RDA5807 is cheaper, includes integrated RDS decoding, and directly drives $32\ \Omega$ headphones without needing external op-amps.