DTMF Decoder Click

How does it work?

DTMF Decoder Click as its foundation uses the MT8870D, an integrated DTMF receiver with enhanced sensitivity from Microchip Technology. It offers low power consumption and high performance and consists of a band split filter section, which separates the high and low group tones, followed by a digital counting section that verifies the received tones’ frequency and duration before passing the corresponding code to the output bus.

This Click board™ has two ways to detect tones: with a mobile phone with a 3.5mm jack which provides the DTMF signals to MT8870D decoder, or using an onboard microphone used to listen the DTMF tones generated by the cell phone. The MT8870D uses digital counting techniques to detect and decode all 16 DTMF tone-pairs into a 4-bit code.

DTMF Decoder Click communicates with MCU using standard I2C 2-Wire interface, with a clock frequency up to 100kHz in the Standard and 400kHz in the Fast Mode. Using the PCA9536 port expander that communicates with the MCU via I2C communication, it is possible to visually display, in binary form, the digit of the pressed number. The digit in binary form is then visually displayed using four red LEDs, labeled from Q1 to Q4, located in the board’s upper right corner.

This Click board™ also has a power-down feature routed on the CS pin of the mikroBUS™ socket labeled as PWD. A logic high applied to pin PWD will power down the device to minimize the power consumption in a Standby mode, which stops the oscillator and the filters’ functions. Also, it uses the interrupt pin of the mikroBUS™ labeled as STD with an additional LED indicator signaling that a received tone pair has been registered, and INH pin, which inhibits the detection of tones representing characters A, B, C, and D. The output code will remain the same as the previously detected code.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to properly use the I2C communication lines. However, the Click board™ comes equipped with a library containing easy-to-use 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 DTMF Decoder Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
Inhibit Mode	INH	2	RST	INT	15	STD	New Tone Indicator
Power Down Mode	PWD	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

DTMF Decoder Click electrical specifications

Software Support

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

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

Library Description

This library contains API for DTMF Decoder Click driver.

Key functions:

• dtmfdecoder_cfg_setup – Config Object Initialization function.
• dtmfdecoder_init – Initialization function.
• dtmfdecoder_default_cfg – Click Default Configuration function.

Examples description

This example shows the basic tone capture of DTMF frequencies, decoding and representing them on the UART LOG.

The application is composed of three sections :

void application_task ( void ) {
    uint8_t result;
    
    if ( dtmfdecoder_delayed_steering_check( &dtmfdecoder ) ) {
        result = dtmfdecoder_tone_read( &dtmfdecoder );
        log_printf( &logger, " Detected key tone:t%crn", result );
        Delay_ms( tone_register_delay );
    }
}

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

Other mikroE Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.DTMFDecoder

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. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika 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.