DTMF
Detector/Generator
by DNA Enterprises, Inc.

Software Overview

DNA Enterprises' DTMF Detection/Generation package implements a multi-channel DTMF generator and 
receiver. The number of channels is configurable at compile time and each transmit channel is 
individually configurable. This package is developed for the TMS320C3x digital signal processor.  
DTMF signals are generated and detected as specified by ITU-T Recommendations Q.23 and Q.24.
The software's modular design separates signal detection and generation issues from data I/O and 
command I/O issues. This allows the DTMF software to "bolt" into custom hardware platforms. Data 
memory requirements for this algorithm are based on the number of channels configured. Less data 
memory is used if fewer channels are required.

Features and Benefits

•	Simultaneously generates and detects DTMF on up to 24 channels 
•	Modular design allows custom I/O development
•	Transmits/detects tones according to ITU-T Recommendations Q.23, Q.24
•	Number of channels is configurable
•	Supports stack or register parameter passing

Processor and System Specifications

Target processor:
TMS320C3x DSP
Algorithm category:
Telecommunications
Program memory usage:
514 words
Data memory usage:
1032 words (based on 24 channels)
Transmitter processor loading:
0.149 MIPS (per channel)
Receiver processor loading: 
0.396 MIPS (per channel)
Data coding format:
13-bit linear PCM at 8 kHz

Algorithm Verification

DNA Enterprises' DTMF algorithm was validated on a third-party PC plug-in board using a 33-MHz 
TMS320C3x according to  ITU-T Recommendations Q.23 and Q.24.  The following receiver tests were 
included in the test suite:
•	DTMF tone detection
•	DTMF tone detection with 10-ms signal interruptions
•	DTMF tone rejection at low levels
•	DTMF tone rejection due to large frequency offsets
•	DTMF tone rejection due to short signal durations
•	Disturbing tone rejection at low levels
•	Low- and high-frequency tone rejection at high levels
•	DTMF tone detection in the presence of echoes
•	DTMF tone detection in the presence of dial-tone signals
•	DTMF tone detection in the presence of Gaussian noise
•	Mitel speech talk off test

Availability

•	Available now on the TMS320C3x DSP
•	Licensable in object or source-code format

DNA Enterprises offers consulting services to tailor the DTMF Detector/Generator software package 
to your specific needs. This includes porting the algorithm to another Texas Instruments DSP.

Company Background and Contact Information

DNA Enterprises Inc. specializes in telecommunication and real-time multiprocessor embedded 
systems. We provide turnkey design and development, offering software, hardware, and digital signal 
processing expertise for all project phases.

Contact:	Mr. Brian Berger
		269 West Renner Parkway
		Richardson, Texas  75080
		(214) 644-3301
		Fax: (214) 644-6338
		e-mail: info@dna.metronet.com