# FM transmitter module, SI4713, I2C, 3-5VDC

> FM transmitter module based on Si4713, controlled via I2C interface, 3-5VDC power supply. Compatible with Arduino, ESP32 and other development boards. Allows stereo audio transmission via 3.5mm AUX input and RDS data (song title, text messages). Typical range up to 10 meters, extendable with an antenna. Operating temperature -25 to 85 degrees C, dimensions 40 x 20 x 7mm.

- Page: https://sigmanortec.ro/en/fm-transmitter-module-si4713-i2c-3-5vdc
- Price: 56.04 RON
- Availability: In stock; 1-2 zile
- Reference: 9518 · EAN: 5945284132052
- Category: Mechatronics and IoT > Sensors and Modules > RF and Radio Modules
- Specifications: Supply Voltage: 3 V; Maximum Input Voltage: 5 V; Input Voltage Type: “DC” in Romanian can mean **“de ce”**, which translates to **“why”** in English.
- Package (shipping data): 0.006 kg
- Updated: 2026-09-23
- Shop: [Sigmanortec.ro](https://sigmanortec.ro/en/llms.txt)
- Prices: RON, VAT included; prices and stock as of 2026-10-22 03:25 (Europe/Bucharest)

## Description

FM transmitter module with Si4713 for Arduino projects and other boards, controlled via I2C, allows stereo audio output via AUX input and sending RDS information such as song title or messages. It operates at 3-5VDC for easy integration, offers software setting of the frequency and transmission power, with a typical range of up to 10 m which can be increased with the antenna.
FM radio transmitter module based on Si4713, with I2C interface, compatible with Arduino, ESP32, and other development boards.
This board can transmit audio and RDS (Radio Data System), a protocol that allows the integration of digital information into FM radio broadcasts. Through RDS, the transmitter can send information to the receiver such as the currently playing song title, station name, metadata, and other text messages.
The power supply voltage between 3 and 5VDC makes it compatible with most development boards available on the market.
It features a stereo AUX input 3.5mm and separate Left/Right channel inputs for good sound quality.
The module operates together with a microcontroller, through which the transmission frequency, transmission power, and transmitted RDS data are controlled.
Usage note: For correct module initialization, we recommend using the modified Adafruit Si4713 library available at: https://github.com/yo3hjv/Adafruit-Si4713-Library — this resolves a timing issue present in the original library and ensures stable initialization on both Arduino and ESP32.
Hardware recommendation: To eliminate instability caused by RF ground loops, it is recommended to install a 6.8K ohm resistor between the RST pin of the module and GND.
Specifications:
Power supply voltage: 3 - 5VDC
Integrated circuit: Si4713
Communication interface: I2C
Band: FM
Transmission: Audio, RDS/RBDS Data
Transmission range: Up to 10 meters, can be improved with an antenna
Audio input: AUX-IN, stereo 3.5mm
Operating temperature: -25 - 85 degrees C
Dimensions mm: 40 x 20 x 7mm
Pins:
Pin
Description
LIN
Left channel audio input
RIN
Right channel audio input
VIN
Power supply 3–5V DC
GND
Common ground (power and logic)
3VO
Integrated regulator output 3.3V DC, max 100mA
RST
Reset (active LOW)
CS
I2C address select: HIGH = 0x63 (default), GND = 0x11
SCL
I2C Clock
SDA
I2C Data
GPIO1/2
General purpose pins, can control LEDs or other external functions
Usage:
Requirements:
- SI4713 Module
- Arduino Uno / ESP32 or other microcontroller
- USB cable
- Arduino IDE installed
- Library: Adafruit Si4713 (modified version)
Download: https://github.com/yo3hjv/Adafruit-Si4713-Library
- Optional: 6.8K ohm resistor (recommended for RF stability)
- Optional: antenna for longer range
Library installation:
Download the ZIP archive from the link above.
In Arduino IDE: Sketch → Include Library → Add .ZIP Library
Select the downloaded ZIP file.
The library is now available.
The original Adafruit library contains a timing difference that can cause failed or random initialization. The above version fixes this issue according to the Silicon Labs datasheet.
Frequency selection (FM):
Frequency (MHz)
Function value
Example call
87.5 MHz
8750
tuneFM(8750)
95.0 MHz
9500
tuneFM(9500)
100.0 MHz
10000
tuneFM(10000)
102.3 MHz
10230
tuneFM(10230)
108.0 MHz
10800
tuneFM(10800)
Transmission power setting:
dBuV Value
Example call
Description
88
setTXpower(88)
Minimum power, very short range
100
setTXpower(100)
Medium power
115
setTXpower(115)
Maximum power (~10m without antenna)
Troubleshooting:
Module not found at radio.begin(): Check SDA, SCL, RST, and CS. CS must be connected to 3.3V for address 0x63.
Random initialization, sometimes works, sometimes not: Use the modified library from the recommended link (timing issue in original library).
Unstable RF signal, fluctuations, noise: Install a 6.8K ohm resistor between RST and GND to eliminate ground loops.
No audio, transmission but no sound: Connect the audio source to the AUX input (stereo 3.5mm jack, line-level signal).
Short transmission range: Set setTXpower(115) and add an antenna to the ANT pin of the module.
Microcontroller pinout:
Module Pin
Arduino Uno
ESP32
Note
VIN
5V
3.3V
Power supply
GND
Common ground
SDA
A4
GPIO21
I2C Data
SCL
A5
GPIO22
I2C Clock
RST
D12
GPIO13
Module reset (ESP32: safe pin, non-strapping)
CS
3.3V
I2C address = 0x63 (default)
CS → GND → I2C address = 0x11
CS → 3.3V → I2C address = 0x63 (default)