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This module shows the implementation of a DTMF detector using the DSK6713. The detector is desgined using Simulink.

Introduction

The Dual-tone multi-frequency (DTMF) signaling method was developed originally to replace pulse (Dial Pulse or DP in the U.S. ) and loop disconnect (LD) signaling methods to dial numbers, in order to shorten the holding time of the switch during dialing , specially for long distance calls.

DTMF signaling uses two tones to represent each key on the touch pad. There are 12 distinct tones The DTMF method defines four additional digits: “A”, “B”,”C”&“D”. Most of the systems today do not use those digits. (Please refer to Table 1). When any key is pressed the tone of the column and the tone of the row are generated. As an example, pressing the '5' button generates the tones 770 Hz and 1336 Hz. The frequencies were chosen to avoid harmonics: no frequency is a multiple of another, the difference between any two frequencies does not equal any of the frequencies, and the sum of any two frequencies does not equal any of the frequencies.

DTMF Frequencies
. 1209 Hz 1336 Hz 1477 Hz
697 Hz 1 2 3
770 Hz 4 5 6
852 Hz 7 8 9
941 Hz * 0 #

Table 1- DTMF frequencies

The low frequencies are referred as rows, The higher frequencies are referred as columns.

This example will show the implementation of a DTMF receiver using the DSK6713. The DTMF receiver will be based on the simulation model used in the Simulink demo. A graphic user interface (GUI) will also be created to activate the DSK6713. DTMF digits will be sent from the PC sound card.

Simulation

The simulation model

Figure 1 shows the model used to simulate DTMF detection and generation.

DTMF Simulation

The DTMF generator is composed by 7 sine wave generators, corresponding to the 7 DTMF frequencies. The oscillators are grouped as described in Table 1. The oscillators’’ outputs are multiplexed and summed (Please refer to Figure 2). Upon selection of a digit to be transmitted, the correspondent oscillators are activated.

DTMF Generation

The DTMF detection comprises two processes, the frequency detection algorithm itself, and a leading edge detection subsystem.

The frequency detection subsystem measures the energy present at the seven frequencies, and calculates the digit by taking the component of maximum energy in the lower and upper frequency groups. The process is shown in Figure 3. This process runs continuously; however the calculated digit is reported only if its energy is above a threshold as determined by the leading edge detection subsystem. The DTMF detection process is shown in Figure 4.

Frequency Detection
DTMF Detection

Running the simulation

  • Open the simulation model “DTMF.mdl”
  • In order to select the digit double click the DTMF generator subsystem and enter the digits to be sent as follows:
"Dialing" DTMF Digits
  • Activate the simulation, the detected digits will be displayed as shown:

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, From matlab and simulink to real-time with ti dsp's. OpenStax CNX. Jun 08, 2009 Download for free at http://cnx.org/content/col10713/1.1
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