FM Click

How does it work?

FM Click is based on the Si4703, a broadcast FM radio tuner from Silicon Labs. The radio tuner works in a worldwide FM band from 76-108MHz, whereas for antenna, it uses headphones. The stereo audio connector supports three and four-conductor earphones with a recommended cable length from 1.1m to 1.45m for the best signal reception. The Si4703, one of the industry’s smallest FM tuners, comes with a 32.768KHz reference clock for better frequency tolerance.

It has two audio outputs, left and right. Each output uses an LM4864, an audio power amplifier from Texas Instruments, to amplify the channel outputs. These amplifiers can deliver about 200mW of continuous average power into an 8Ω load. The FM Click is used as a stereo device, but as mono also.

The FM Click can communicate to the host MCU over the I2C serial interface of the mikroBUS™ socket. Besides communication pins, this board also uses several others. The SEN pin, routed to the CS pin of the mikroBUS™ socket, serves as a serial interface activation signal, which, combined with I2C pins, forms a 3-wire interface. The RST pin is used as a general reset feature alongside two user-configurable pins, GP2 and GP1, routed to the AN and INT pins of the mikroBUS™ socket. These I/O pins can be used as interrupt requests (seek/tune or RDS ready) or as stereo/mono indicators.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on FM Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
General Purpose I/O	GP2	1	AN	PWM	16	NC
Reset	RST	2	RST	INT	15	GP1	General Purpse I/O
Serial enable input	SEN	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	CLK	Serial clock input
	NC	6	MOSI	SDA	11	DIO	Serial data input
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

FM Click electrical specifications

Software Support

We provide a library for the FM Click as well as a demo application (example), developed using Mikroe compilers. The demo can run on all the main Mikroe development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for FM Click driver.

Key functions

• This function reads recived signal strength indicatior

• This function calculates current channel frequency based on band and space settings

• This function reads CHANNEL bits from READCHAN register

Example Description

This click represent FM radio tuner which supports worldwide FM band (76 – 108 MHz) and has a set of features such as automatic frequency and gain control, seek tuning and volume control.

 void application_task ( void ) 
 {  
     fm_case_station_1( &fm ); 
     Delay_ms( 10000 ); 

     fm_case_station_2( &fm ); 
     Delay_ms( 10000 ); 

     fm_case_station_3( &fm ); 
     Delay_ms( 10000 ); 

     fm_case_station_4( &fm ); 
     Delay_ms( 10000 ); 

     fm_case_station_5( &fm ); 
     Delay_ms( 10000 ); 
 }

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended), downloaded from our LibStock™ or found on Mikroe github account.

Other Mikroe Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.Fm

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 Click or RS232 Click to connect to your PC, for development systems with no UART to USB interface available on the board. UART terminal is available in all Mikroe compilers.

mikroSDK

This Click board™ is supported with mikroSDK – Mikroe Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.