Si4703 FM Radio Receiver Quickstart Guide

Time to Rock

This Si4703 FM Tuner Eval Board breaks out the Silicon Laboratories Si4703 FM tuner chip. Beyond being a simple FM radio, the Si4703 is also capable of detecting and processing both Radio Data Service (RDS) and Radio Broadcast Data Service (RBDS) information. The Si4703 even does a very good job of filtering and carrier detection, or rather, it’s good at detecting when a station is coming in clear. It also enables data such as the station ID and song name to be displayed to the user.

Using this board, we are able to pick up multiple stations just as well as with a standard FM radio. The board breaks out all major pins and makes it easy to incorporate this great chip into your next radio project. Also, by plugging headphones into the 3.5mm audio jack, you effectively use the cable in your headphones as an antenna! Therefore, this board does not require an external antenna if using headphones or a 3.5mm audio cable longer than 3 feet.

This quickstart guide will lead you through assembling the radio receiver, hooking it up to an Arduino platform, and getting an Arduino to talk to the Si4703. The Arduino sketch will illustrate how to set the radio receiver to tune an FM frequency, and we’ll be able to change the station and the volume using the serial terminal in Arduino. There will be some extra hardware required for the example: headphones or speakers, some wire, and an Arduino Pro 3.3V (or similar platform) will get you through the basic example.

Software Required

Hardware Required

Firmware Required

Relevant Documentation

  • Checkout the main product page for much more documentation, like the datasheets for the parts on the device, more programming examples, and a programming guide for the radio receiver chip from the manufacturer.

Assembly Guide

The assembly of the radio receiver is quick and easy. In order to interface with the radio receiver we’ll need to interact with the pins on the board. All of the pins that we need are accessible from the header holes located along the side of the radio receiver board. You have a couple of options for interfacing to the board: you can solder wires directly to these holes or you can solder male or female headers to the holes and then connect them to a microcontroller using jumper wires. I go for female headers because then a simple wire can be used to connect the radio receiver to an Arduino board, and it keeps the radio receiver more usable without wires soldered semi-permanently to it. So pick your method, and start soldering! If you’ve never soldered before, check out this tutorial to pick up a new skill. Below are some pictures of how my radio receiver turned out after soldering on the headers.


Hooking It Up

The method that we are going to use to communicate with the radio receiver requires that we use five wires to connect an Arduino Mini to the radio receiver. Below is a table which defines the pin connections that need to be made, and a fritzing diagram of the connections should also help you get your wires connected properly. If you look at the back of your radio receiver board you’ll notice that next to each header hole is a small label. These signal names indicate how each pin is being used by the radio receiver, and also how they can be used to interact with a microcontroller. For now, just make sure you match the signal name on the radio receiver board to the correct Arduino pin number.

Arduino Pin Receiver Pin
3.3V VCC

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It’s very important to realize that the Si4703 radio receiver breakout is a 3.3V device; that’s why we’re using an Arduino Mini Pro 3.3V. Using a 5 Volt Arduino (like the Arduino) can ruin the radio receiver if proper care isn’t taken to shift the voltage levels down to an acceptable level. You can read this sensor interfacing tutorial to learn how to connect modules that communicate at different voltage levels.

Arduino Example: Tuning Stations and Setting Volume

In this example we’re going to use an Arduino with the radio receiver to tune a radio station. The sketch will also allow us to use the serial port to change the station and raise or lower the volume. We’ll be using the sample code located in the Si4703 Arduino Library. If you haven’t downloaded the Si4703 Library, you can grab it here. Unzip the folder into your Arduino Libraries folder so that you have a folder in the libraries directory which is called “Si4703.” Once you’ve downloaded and unzipped the library, go ahead and open Arduino. Once the software has booted up, go to File->Examples->Si4703->Si4703_Example; this will load the first example sketch. You can upload the sketch and plug in some headphones to start playing around with the radio, or continue reading to learn how the sketch works!

Once you’ve opened the sketch you’ll notice a big section of comments at the top. Read through these comments to understand what the sketch does. The code for our example sketch is pretty simple since we’re taking advantage of the Si4703 library functions. First let’s look at the initialization and setup of the sketch.

//Add the Si4703 Library to the sketch.
#include <Si4703.h>
#include <Wire.h>

//Create an instance of the Si4735 named radio.
Si4703 radio;

void setup()
  //Create a serial connection

  //Initialize the radio to the FM mode (Possible modes are AM, FM, SW, LW).
  //The mode will set the proper bandwidth. Ensure that the antenna
  //switch on the shield is configured for the desired mode.

  //Set the FM Frequency to 97.3 MHz

The setup and initialization is pretty easy. We start by including the Si4703 and Wire libraries. The Wire library is needed for I2C communication, which is what is used to talk to the radio receiver. The Si4703 library has the functions we need to control the radio receiver. Next we create a variable (or instance) of the Si4703 library called ‘radio.’ In the setup section all we do is create a serial connection, and use the ‘begin’ function of the radio library to initialize the Si4703. Finally we tell the Si4703 to tune to 97.3 MHz. Once things are set up, we get into the loop routine which handles the serial communication and sending commands to the Si4703.

void loop()
  //Wait until a character comes in on the Serial port.
    //Decide what to do based on the character received.
      //If we get the number 8, turn the volume up.
      case '8':radio.volume(UP);
      //If we get the number 2, turn the volume down.
      case '2':radio.volume(DOWN);
      //If we get the number 4, seek down to the next channel in the current bandwidth (wrap to the top when the bottom is reached).
      case '4';
      //If we get the number 6, seek up to the next channel in the current bandwidth (wrap to the bottom when the top is reached).
      case '6';
      //If we get the letter m, mute the radio.
      case 'M':
      case 'm':radio.toggleMute();
} //End main loop

The loop routine is also pretty straightforward. The loop waits for input from the serial terminal. Once a character is received, a decision is made. Depending on what the character is one of the library functions for the Si4703 is executed.


To find out what other functions there are in the Si4703 library, go into your libraries folder for Arduino (the same one you unzipped the folder in) and open the Si4703.h file with a text editor. This file will tell you all of the functions that exist in the library. Play around with it, and if you come up with some cool new functions for the library mention it in the comments so other people can use it as well. Good luck hacking! If you have any problems, feel free to contact SparkFun Technical Support at

Comments 2 comments

  • Having trouble with this.

    “Si4703 does not name a type.” The libraries you link seem to use Si4703_Breakout instead, which has a totally different interface.

    In testing the included sample sketch from the libraries, which uses Si4703_Breakout, on my Pro Micro, I can’t seem to get any serial output. I know the serial works, but initializing the radio seems to kill it somehow.

    My setup is 2->SDIO 3->SCLK 7->RST VCC->3V3 GND->GND