What is FM Receiver, How to build an Arduino FM Radio with RDA5807

By Shawn 5 years ago

FM Receiver is a device used for FM radio communications, commonly found nowadays in modules such as RDA5807 and tea5767. These miniaturized FM receiver modules come in a small package that’s suitable for microcontroller usage and building a simple Arduino FM Radio.

Hence, we’ll be exploring how you can build a simple FM radio in today’s FM receiver guide. However, we’ll first have to understand more about what is FM receiver and its usages.

What is a FM Receiver?

Sony FM Radio

Based on the earlier introduction, we understand that the FM (frequency modulation) receiver is a device used for Radio communications, but here’s more to it!

  • In radio communications, there are two types of radio transmission; FM AM
    (amplitude modulation) receiver. Comparing both, FM is less subjected to interference to AM, with better sound quality and higher bandwidth.

For radio communications to take place, it involves three steps as well; detecting, receiving, and converting radio waves to the desired information. That’s where an FM receiver comes to play; receiving radio waves and converting them into an output where information is usable.

The components of FM receivers and its functionality help achieve that:

  • An antenna: To firstly detect the frequency waves
  • Electronic filters; To separate the required radio waves from all the other forms of frequency waves detected
  • Amplifier: Used to increase the power of the radio signal

How does FM receiver work?

FM Receiver Block Diagram Explained

Simplified FM receiver block diagram

To easily understand how an FM receiver work, let’s explain a simplified FM receiver block diagram!

1. RF amplifier

  • The rf amplifier receives the desired signal from the antenna and provides tuning to remove the image signal alongside all unwanted signals on other frequencies. It then amplifies the desired signal

2. Mixer

  • The desired signal is then entered to this block, involving the oscillator and mixer to form a frequency changer circuit, such that required frequency can be converted

3. IF amplifier and Filter

  • The filtering process filters the immediate frequency outputted from the mixer and amplified it for the next stage

4. Demodulator

  • The amplified IF signal travels to the demodulator, beginning the process of demodulation
  • Demodulation can be in any form of modulation, ranging from amplitude modulation, frequency modulation, etc.

5. Audio amplifier

  • After demodulation, the recovered audio is applied to an audio amplifier block, ending the process by amplifying it to the required level for loudspeakers/headphones

FM receiver applications

Although FM receivers are made for radio applications, such as radio broadcasting, it’s still applicable and used in a variety of other electronic systems. Here are some of its applications:

Smartphones

Do you know most smartphones on the market have inbuilt FM receivers? Yes indeed! But sad to say for iPhone users, it does not exist as its hardware does not support it. For others like Andriod, you can simply download the NextRadio app that allows for the FN chip usage!

Satellite Communication

Data transmission/communication between satellites include FM receiver and transmitter that help with long-distance telephone calls, space station broadcasts, spacecraft direct broadcasting that sends signals of satellite radio receivers for consumers, etc.

Modems

FM receivers are found in radio modems, creating private radio networks (PRN) through transferring wireless data across a range of up to tens of kilometers. Such modems are key in industrial usages, where real-time data communication is needed.

So long as applications that require high reliability of data transfer and very high uptime, radio communications are picked.

Introduction to RDA5807

RDA5807 Chip

Remembered when I mentioned the RDA5807 being a common miniaturized FM receiver? Now let’s take a look at what it’s all about!

The RDA5807M series is the newest generation single-chip broadcast FM stereo radio tuner with a fully integrated synthesizer. Its FM receiver uses a digital low-IF architecture that’s low-cost yet avoiding the difficulties with direct conversion!

Its features include:

  • The integrated low noise amplifier supports a worldwide broadcast band of 50 to 115MHz
  • The synthesizer has a fully integrated on-chip RF, IF VCO, and an on-chip loop filter
  • Digital low IF tuner
  • Support for RDS/RBDS
  • Support for 32.768KHz crystal oscillator
  • Autonomous search tuning
  • Direct auto gain control (AGC)
  • Digital adaptive noise cancellation

For more information, you can visit the RDA5807M datasheet here!

RDA5807 vs TEA5767

As compared to the TEA5767, it boasts advantages on the following factors:

  • RDA5807 requires lesser external components for usage
  • Additional embedded audio power amplifier that’s loadable with 32 Ohm speakers
  • Bonus features such as the bass boosting function

Note: Since the RDA5807 chip itself requires a heavy lot of soldering to be used with an Arduino, we recommend an integrated module for easier interfacing!

If you’re already looking for a cheap and simple to use RDA5807 module, we’ve just that here at Seeed!

Grove – I2C FM Receiver v1.1

Since the Grove – I2C FM Receiver v1.1 is based on the RDA5807M, it’ll share similar features like it. But with this integrated module, you’re getting a Grove port and Headset interface.

With the support for Grove and Headset interface, you wouldn’t have to worry soldering an external headphone jack or using jumper wires to build an FM radio. Saving you a whole of trouble with its ease of usage and functionality!

Don’t believe its benefits? See it for yourself!

  • A FM receiver circuit without Grove
  • A FM receiver circuit with Grove

Like how simple it is? Our grove system not only apply for this module, but we’ve over 200 modules that support it!

FM Radio tutorial with the RDA5807

Alright, we’ve gone through the essentials on FM receivers and the RDA5807, so let’s get straight into our tutorial on building an FM radio!

Here’s what you need:

  • Seeeduino is Seeed’s very own Arduino board, made with relative benefits over the original
    • Arduino UNO is suitable to be used for this tutorial
  • As Seeeduino V4.2 only has 3 grove ports, you’ll require the Grove-Base Shield to house all modules

Before we begin configuring the hardware, do take note of the following:

  • Please use the USB cable with 4 wires inside, instead of the 2 wires cable as it can’t transfer data. If you are not sure about the wire you have, you may click here to buy
  • Each Grove module comes with a Grove cable, but if you lose it, you may click here to buy

Hardware configurations:

  • Step 1: Connect Grove – I2C FM Receiver v1.1 to port IIC OF Grove-Base Shield.
  • Step 2: Connect the first Grove button to D2 port and connect the other button to D3 port
  • Step 3: Connect Grove – Rotary Angle sensor to A0 port of Grove – Base Shield
  • Step 4: Plug Grove – Base Shield into Seeeduino
  • Step 5: Plug the earphone or speaker to the 3.5mm jack of Grove – I2C FM Receiver
  • Step 6: Connect Seeeduino to PC via a USB cable

It should look something like this after completing the above steps:

Software configurations:

/*
 * I2C_FM.ino
 * Demo code for the Grove-I2C_FM_Receiver module
 *
 * Copyright (c) 2012 seeed technology inc.
 * Author     : Jack Shao ([email protected])
 * Create Time: Jul 2014
 * Change Log :
 *
 * The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
//
/*
 * Modifications to the I2C_FM.ino by Mel Patrick - Wabbit Wanch Design
 * Modified routines for scanning UP or DOWN through the FM band
 * Modified routine to test for signal strength of received station
 * Modified routines to support bass boost and MONO signal
 * RSSI, read it too soon after setting a station and you get a small value
 * so it's better to wait a bit (50ms) and try it. minSignalStrength will
 * skip locking on a station with a weak signal (you could set the MONO bit) to get
 * better reception on these stations.
 */
#include <Arduino.h>
#include <Wire.h>
#include <EEPROM.h>

#define BTNUP          2// used for seeking UP (normally CLOSED push button)
#define VOL_POT        A0// volume POT LOG taper 10K
#define BTNDN          3// used for seeking DOWN (normally CLOSED push button)

uint16_t gChipID = 0;
uint8_t RDA5807P_REGW[10];

#define I2C_ADDR       0x10

#define READ            1
#define WRITE           0

#define ADRW            0x20
#define ADRR            0x21
//

//#define                 _SHARE_CRYSTAL_24MHz_
//#define                 _SHARE_CRYSTAL_12MHz_
#define                 _SHARE_CRYSTAL_32KHz_
//#define                 _FM_STEP_50K_

//5807M,5807FP,5807NN,5807NP
uint8_t RDA5807N_initialization_reg[]={
#if defined(_SHARE_CRYSTAL_24MHz_)
  0xC4, 0x51, //02H:
#elif defined(_SHARE_CRYSTAL_12MHz_)
  0xC4, 0x11, //02H:
#elif defined(_SHARE_CRYSTAL_32KHz_)
  0xC4, 0x01,//change 01 to 05 enables the RDS/RBDS
#else
  0xC0, 0x01,
#endif
  0x00, 0x00,
  0x04, 0x00,
  0xC3, 0xad,  //05h
  0x60, 0x00,
  0x42, 0x12,
  0x00, 0x00,
  0x00, 0x00,
  0x00, 0x00,  //0x0ah
  0x00, 0x00,
  0x00, 0x00,
  0x00, 0x00,
  0x00, 0x00,
  0x00, 0x00,
  0x00, 0x00,  //0x10h
  0x00, 0x19,
  0x2a, 0x11,
  0xB0, 0x42,
  0x2A, 0x11,  //
  0xb8, 0x31,  //0x15h
  0xc0, 0x00,
  0x2a, 0x91,
  0x94, 0x00,
  0x00, 0xa8,
  0xc4, 0x00,  //0x1ah
  0xF7, 0xcF,
  0x12, 0x14,  //0x1ch
  0x80, 0x6F,
  0x46, 0x08,
  0x00, 0x86,  //10000110
  0x06, 0x61,  //0x20H
  0x00, 0x00,
  0x10, 0x9E,
  0x23, 0xC8,
  0x04, 0x06,
  0x0E, 0x1C,  //0x25H     //0x04 0x08
};

int16_t freq = 10110;
uint16_t vol = 1;
//
// added items - Mel
boolean bassBit = true;// bass boost
boolean monoBit = false;// force MONO not stereo
const boolean seekUP = true;
const boolean seekDN = false;
uint8_t minSignalStrength = 36;// anything below this probably set a MONO flag for better reception
uint8_t signalStrength;
long previousMillis = 0;// last time the function was called
long interval = 2000;// interval for the signal level function (2 seconds)
int8_t stationStep = 10;// kHz steps bewteen the stations (North America = 10)
boolean hasVolumePot = true;// flag if you have a POT attached or not
//
void setup()
{
  Wire.begin();
  loadDefaults();// load any defaults from previous radio settings
  Serial.begin(9600);
  Serial.println("Started");
  //=======================
  //rda5807 power on
  RDA5807P_PowerOnReset();
  RDA5807P_SetMute(false);

  //=======================
  pinMode(BTNUP, INPUT_PULLUP);
  pinMode(VOL_POT, INPUT);
  pinMode(BTNDN, INPUT_PULLUP);
  //=======================
  RDA5807P_SetVolumeLevel(vol);// use this if you don't have a POT for volume attached (0-15)
  RDA5807P_SetFreq( freq );
}

void loop()
{
  unsigned long currentMillis = millis();

  if(currentMillis - previousMillis > interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;
    showSignalStrength();
  }
  //
  if (digitalRead(BTNUP) == 1)
  {
    delay(100);
    if (digitalRead(BTNUP) == 1)
      fmSeek(seekUP);
    while(digitalRead(BTNUP) == 1);
  }
  if (digitalRead(BTNDN) == 1)
  {
    delay(100);
    if (digitalRead(BTNDN) == 1)
      fmSeek(seekDN);
    while(digitalRead(BTNDN) == 1);
  }
  if (hasVolumePot == true) setVolume();// use this to read the POT
}
//
void setVolume() {
  unsigned int temp_vol;
  temp_vol = analogRead( VOL_POT );
  if (abs(temp_vol - vol)>5)
  {
    if (vol != temp_vol) {// don't bother changing the volume if unless the pot moves
      vol = temp_vol;
      unsigned char hex_vol = map(vol, 0, 1023, 0, 0xf);
      RDA5807P_SetVolumeLevel(hex_vol);
      saveDefaults();// save new volume to EEPROM
    }
  }
}
//
void fmSeek(boolean theDir) {
  int signalStrength;
  if (!theDir) {
    Serial.println("Start seeking down...");
  }
  else
  {
    Serial.println("Start seeking up...");
  }
  do {
    do{
      if (theDir == seekUP) {
        freq += stationStep;
      }
      else
      {
        freq -= stationStep;
      }
      if (freq > 10800) freq = 8800;
      if (freq < 8800) freq = 10800;
      //Serial.println(freq);
    }
    while(!RDA5807P_ValidStop(freq));
    delay(50);
    signalStrength = RDA5807P_GetSigLvl(freq);// max is 63 according to Data sheet, but I've seen more
  }
  while (signalStrength < minSignalStrength);// minimum signal strength, keep looking
  showRadioStation();
  saveDefaults();// save new station selection to EEPROM
}
//
void showRadioStation() {
  Serial.print("Stable Freq:");
  Serial.print(((float)freq)/100.0f);
  Serial.println("MHz");
}
//
void showSignalStrength() {
  signalStrength = RDA5807P_GetSigLvl(freq);// max is 63...as noted
  Serial.print("Signal Strength: ");
  Serial.println(signalStrength);
}

//===========================================================
// FM functions
//===========================================================
unsigned char OperationRDAFM_2w(unsigned char operation, unsigned char *data, int numBytes)
{
  if(operation == READ)
  {
    Wire.requestFrom(I2C_ADDR, numBytes);
    for(int i=0;i<numBytes;i++)
    {
      *data++ = Wire.read();
    }
  }
  else
  {
    Wire.beginTransmission(I2C_ADDR);
    for(int i=0;i<numBytes;i++)
    {
      Wire.write(*data++);
    }
    Wire.endTransmission();
  }
  return 0;
}


/**
 * @brief Reset RDA5807P while power on RDA5807P
 * @author RDA RDA Ri'an Zeng
 * @date 2008-11-05
 * @param void
 * @return void
 * @retval
 */
void  RDA5807P_PowerOnReset(void)
{
  RDA5807P_Intialization();
}

/**
 * @brief RDA5807P power off function
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param void
 * @return void
 * @retval
 */
void  RDA5807P_PowerOffProc(void)
{
  RDA5807P_REGW[1] &= (~1);
  OperationRDAFM_2w(WRITE, &(RDA5807P_REGW[0]), 2);
}

/**
 * @brief Set RDA5807P into mute mode
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param bool mute: if mute is true,then set mute; if mute is false,then set no mute
 * @return void
 * @retval
 */
void RDA5807P_SetMute(boolean mute)
{
  if(mute)
    RDA5807P_REGW[0] &=  ~(1<<6);
  else
    RDA5807P_REGW[0] |= 1<<6;
  RDA5807P_REGW[0] |= monoBit<<5;
  RDA5807P_REGW[0] |= bassBit<<4;
  OperationRDAFM_2w(WRITE, &(RDA5807P_REGW[0]), 2);//RDA5807M_REGW
  delay(50);    //Dealy 50 ms
}
//
/*************************************************
 * @brief Set frequency function
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param int16_t curFreq:frequency value
 * @return void
 * @retval
 ***********************************************/
void RDA5807P_SetFreq(int16_t curFreq)
{
  uint16_t curChan;
  curChan=RDA5807P_FreqToChan(curFreq);

  if((curFreq >= 6500)&&(curFreq < 7600))
  {
    RDA5807P_REGW[3] = 0x0c;
  }
  else if((curFreq >= 7600)&&(curFreq < 10800))
  {
    RDA5807P_REGW[3] = 0x08;// sets the BAND bits (00xx = 87-108, 01xx=76-91, 10xx=76-108, 11xx=65-76
    // for north america this must be set to 10xx for some unknown reason
  }
  //SetNoMute
  RDA5807P_REGW[0] |= 1<<6;
  RDA5807P_REGW[0] |= monoBit<<5;
  RDA5807P_REGW[0] |= bassBit<<4;
  //handleBits();
  RDA5807P_REGW[2]=curChan>>2;
  RDA5807P_REGW[3]=(((curChan&0x0003)<<6)|0x10) | (RDA5807P_REGW[3]&0x0f);    //set tune bit

  OperationRDAFM_2w(WRITE, &(RDA5807P_REGW[0]), 4);
  delay(50);     //Delay five ms
  showRadioStation();
}
//
/**
 * @brief Station judge for auto search
 * @In auto search mode,uses this function to judge the frequency if has a station
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param int16_t freq:frequency value
 * @return bool: if return true,the frequency has a true station;otherwise doesn't have a station
 * @retval
 */
boolean RDA5807P_ValidStop(int freq)
{
  uint8_t RDA5807P_reg_data[4]={
    0                                                  };
  uint8_t falseStation = 0;
  uint8_t i=0;
  uint16_t curChan;

  if((freq >= 6500)&&(freq < 7600))
  {
    RDA5807P_REGW[3] = 0x0c;
  }
  else if((freq >= 7600)&&(freq < 10800))
  {
    RDA5807P_REGW[3] = 0x08;// sets the BAND bits (00xx = 87-108, 01xx=76-91, 10xx=76-108, 11xx=65-76
    // for north america this must be set to 10xx for some unknown reason
  }
  curChan=RDA5807P_FreqToChan(freq);
  //SetNoMute bit 9 is seek direction (0=seek down, 1=seek up).
  //02H 14
  RDA5807P_REGW[0] |=   1<<6;// reg zero is bits 15 to bit 8 (this shifts to bit 14)
  RDA5807P_REGW[0] |= monoBit<<5;
  RDA5807P_REGW[0] |= bassBit<<4;
  //handleBits();
  RDA5807P_reg_data[0]=RDA5807P_REGW[0];
  RDA5807P_reg_data[1]=RDA5807P_REGW[1];
  RDA5807P_reg_data[2]=curChan>>2;//03H 15:8 CHAN
  RDA5807P_reg_data[3]=(((curChan&0x0003)<<6)|0x10) | (RDA5807P_REGW[3]&0x0f);//
  OperationRDAFM_2w(WRITE,&(RDA5807P_reg_data[0]), 4);

  delay(50);    //Dealy 25 ms

  if (0x5808 == gChipID)
    OperationRDAFM_2w(READ,&(RDA5807P_reg_data[0]), 4); //
  else
  {
    do
    {
      i++;
      if(i>5) return 0;

      delay(30);
      //read REG0A&0B
      OperationRDAFM_2w(READ,&(RDA5807P_reg_data[0]), 4);
    }
    while((RDA5807P_reg_data[0]&0x40)==0);
  }

  //check FM_TRUE
  if((RDA5807P_reg_data[2] &0x01)==0) falseStation=1;//0B 8  FM TRUE

  if(freq==9600) falseStation=1;// North America - if scanning DOWN, the radio will lock on 9600 for some reason!
  delay(50);
  if (falseStation==1)
    return 0;
  else
    return 1;
}

/**
 * @brief Get the signal level(RSSI) of the current frequency
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param int16_t curf:frequency value
 * @return uint8_t: the signal level(RSSI)
 * @retval
 */
uint8_t RDA5807P_GetSigLvl( int16_t curf )
{
  uint8_t RDA5807P_reg_data[4]={
    0                                                  };
  OperationRDAFM_2w(READ,&(RDA5807P_reg_data[0]), 4);
  delay(50);    //Delay 50 ms
  return  (RDA5807P_reg_data[2]>>1);  /*??rssi*/
}

/**
 * @brief Set FM volume
 * @It has better use the system volume operation to replace this function
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param uint8_t level: volume value
 * @return void
 * @retval
 */
void RDA5807P_SetVolumeLevel(uint8_t level)
{
  uint8_t RDA5807P_reg_data[8];
  uint8_t i = 0;

  for (i=0;i<8;i++)
    RDA5807P_reg_data[i] = RDA5807P_REGW[i];

  RDA5807P_reg_data[7]=(( RDA5807P_REGW[7] & 0xf0 ) | (level & 0x0f));

  RDA5807P_reg_data[3] &= (~(0x10));//disable tune

  OperationRDAFM_2w(WRITE, &(RDA5807P_reg_data[0]), 8);
  delay(50);    //Dealy 50 ms
}

/**
 * @brief Initialize RDA5807P
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param void
 * @return bool:if true,the operation is successful;otherwise is failed
 * @retval
 **/
boolean  RDA5807P_Intialization(void)
{
  uint8_t error_ind = 0;
  uint8_t RDA5807P_REGR[10]={
    0x0                                                  };
  uint8_t i = 0;

  RDA5807P_REGW[0] = 0x00;
  RDA5807P_REGW[0] |= monoBit<<5;
  RDA5807P_REGW[0] |= bassBit<<4;
  RDA5807P_REGW[1] = 0x02;

  error_ind = OperationRDAFM_2w(WRITE, (uint8_t *)&RDA5807P_REGW[0], 2);//soft reset
  delay(50);

  error_ind = OperationRDAFM_2w(READ, (uint8_t *)&RDA5807P_REGR[0], 10);
  delay(50);

  gChipID = RDA5807P_REGR[8];
  gChipID = ((gChipID << 8) | RDA5807P_REGR[9]);

  Serial.print("Chip ID: 0x");
  Serial.println(gChipID, HEX);

  for (i=0;i<8;i++) {
    RDA5807P_REGW[i] = RDA5807N_initialization_reg[i];
  }

  error_ind = OperationRDAFM_2w(WRITE, (uint8_t *)&RDA5807N_initialization_reg[0], 2); //power up
  delay(600);
  //Serial.println(sizeof(RDA5807N_initialization_reg));
  error_ind = OperationRDAFM_2w(WRITE, (uint8_t *)&RDA5807N_initialization_reg[0], sizeof(RDA5807N_initialization_reg));

  delay(50);         //Dealy 50 ms

  if (error_ind )
    return 0;
  else
    return 1;
}
//
/**
 * @brief Cover the frequency to channel value
 * @author RDA Ri'an Zeng
 * @date 2008-11-05
 * @param uint16 frequency:covered frequency
 * @return uint16: channel value
 * @retval
 * In the United States, frequency-modulated broadcasting stations operate in a frequency band extending from 87.8 MHz to 108.0 MHz,
 * for a total of 20.2 MHz. It is divided into 101 channels, each 0.2 MHz wide, designated "channel 200" through "channel 300."
 * In actual practice, no one (except the FCC) uses these channel numbers; the frequencies are used instead.
 */
uint16_t RDA5807P_FreqToChan(uint16_t frequency) {
  uint8_t channelSpacing = 10;
  uint16_t channel = 0;

  if((frequency >= 6500)&&(frequency < 7600))
  {
    channel = (frequency - 6500)/channelSpacing;
  }
  else if((frequency >= 7600)&&(frequency < 10800))
  {
    channel = (frequency - 7600)/channelSpacing;
  }
  return (channel);
}
//
void loadDefaults() {
  char myCode[9] = "Grove_FM";
  char myInit[9] = "blank123";
  /*
  * byte map in EEPROM
   * 8, 9 the default frequency for a reboot
   * 10, 11 current preset volume of the radio (used if no pot is attached)
   */
  for (int i=0; i < 8; i++) {
    myInit[i] = EEPROM.read(i);// read out to see if the thing is INITIALIZED
  }
  if (strcmp(myCode, myInit) == 0) {// if this is ZERO (we previously wrote some), then read the values
    freq = epReadINT(8);// read back the INT for frequency from eeprom 8 and 9 (two bytes for an INT)
    if (!hasVolumePot) vol = epReadINT(10);// read back the volume setting but don't use it unless flag is false
  }
  else// we don't have any defaults, so we have to save some first
  {
    for (int i=0; i < 8; i++) {
      EEPROM.write(i, myCode[i]);// write this to EEPROM to show we have it saved
    }
    saveDefaults();// write the current default settings
  }
}
//
void saveDefaults() {
  epWriteINT(8, freq);// write the two bytes for INT for a reboot
  epWriteINT(10, vol);// write the current volume POT setting
}
//
void epWriteINT(int where, int theVal) {
  union uData
  {
    byte stuff[2];
    int f1;// 2 bytes of memory
  }
  u;
  u.f1 = theVal;// copy into the union
  for (int j=0; j < 2; j++) {// now we have to write out 2 bytes of memory
    EEPROM.write(where + j, u.stuff[j]);// write it to EEPROM
  }
}
//
long epReadINT(int where) {
  union uData
  {
    byte stuff[2];
    int f1;// 2 bytes of memory
  }
  u;
  for (int j=0; j < 2; j++) {
    u.stuff[j]=EEPROM.read(where + j);// read back the 2 bytes at this memory location
  }
  return u.f1;
}
//
void epWriteLong(int where, long theVal) {
  union uData
  {
    byte stuff[4];
    long f1;// 4 bytes of memory
  }
  u;
  u.f1 = theVal;// copy into the union
  for (int j=0; j < 4; j++) {// now we have to write out 4 bytes of memory
    EEPROM.write(where + j, u.stuff[j]);// write it to EEPROM
  }
}
//
long epReadLong(int where) {
  union uData
  {
    byte stuff[4];
    long f1;// 4 bytes of memory
  }
  u;
  for (int j=0; j < 4; j++) {
    u.stuff[j]=EEPROM.read(where + j);// read back the 4 bytes to this memory location
  }
  return u.f1;
}
  • Step 4: Upload the demo, if you’re unsure on how to upload the code, do refer to our guide
  • Step 5: Open the Serial Monitor of Arduino IDE by clicking Tool -> Serial Monitor or press CTRL + Shift + M on your keyboard.

If everything goes well, you’ll achieve the following result: 

Started
Chip ID: 0x5808
Stable Freq:102.60MHz
Signal Strength: 46
Signal Strength: 46
Signal Strength: 45
Signal Strength: 45
Signal Strength: 45
Signal Strength: 45
Start seeking down...
Stable Freq:94.00MHz
Signal Strength: 44
Signal Strength: 51
Signal Strength: 51
Signal Strength: 50
Signal Strength: 50
Signal Strength: 51

Now you have your own FM radio!

  • To simply change between radio stations, you can press the Grove – buttons
  • To adjust the volume, you can simply rotate the Grove – rotary angle sensor

If you wish, you could design housing boxes to make the whole setup look more like a radio!

Resources and Going Further

If you currently own an RDA5807 chip itself and is looking to build an FM Radio, here are some project tutorials from the Hackster Community!

Grove – I2C FM Receiver v1.1 resources:

Summary

That’s all for today on FM receivers and RDA5807. I hope with today’s blog, you get a deeper understanding of what it is, how it works, usages and how to build an FM radio!

Get started with building your very own FM radio with the Grove – I2C FM Receiver v1.1 today!

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Shawn

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