Telco DTMF Generator/Detector
for TMS320C25/'C5x
by DSP Software Engineering, Inc.

Software Overview

The DTMF software is an implementation of a DTMF generator and DTMF detector for the TMS320C25 and 
TMS320C5x. Dual-Tone Multi-Frequency (DTMF) is an international signaling standard for telephone 
digits (number buttons). The DTMF generator function generates standard telephone digits as the sum 
of sinusoids corresponding to a row and column frequency for each digit. The DTMF detector function 
checks incoming digit signals and uses a series of tests to decode them.
The DTMF software generates and detects 8-kHz linear-PCM samples. DTMF has a variety of uses in 
modern telephone systems. It provides a means of data entry and menu selection for numerous 
applications, including financial transactions, business directories, voice mail, and many other 
menu-driven operations that respond to digits entered from a telephone.

Features and Benefits

•	Scalable output range
•	Exceeds Bellcore and MITEL performance Processor and system requirements
•	Independent C-callable generator and detector functions
•	SPOX compatible
•	Extremely low data and program memory requirements

Processor and System Requirements

•	Devices supported: TMS320C5x
•	Algorithm category: Telecommunications
•	Requirements:
All memory requirements are in units of 16-bit words. The MIPs ratings presented require the listed 
amounts of dual-access RAM (DARAM), zero-wait-state program and data memory and sample by sample  
processing. All measurements were made using an executable demonstration built for a third-party PC 
plug-in board.
Function
Avg MIPS
DARAM
Data
Program
Generator
2.4
0
8
216
Detector 
1.8
41
0
310
Generate & Detect
4.2
41
8
526
* Frame size of 20 samples - performance increases with larger frames.

User Functions

The DTMF implementation consists of two independent, C-callable functions that perform generation 
and detection operations. It also includes a function that initializes the detector. The generator 
and detector interface with linear-PCM samples and DTMF digits.
DTMF Generator/Detector
dtmf_gen (...)
Generates a linear PCM sample for a specified digit
dtmf (...)
Returns DTMF digit-status detected for each linear PCM sample
idtmf (...)
Initializes the DTMF detector

Algorithm Verification

•	Call DSPSE for verification details

Availability

•	Source and object code currently available for licensing.

Company Background and Contact Information

DSP Software Engineering, Inc. is a leading provider of highly-complex digital-signal-processing 
software used in telecommunications and multimedia applications such as computer telephony, digital 
wireless, PSTN, and satellite communications, and videoconferencing.

Contact:	DSP Software Engineering, Inc
		175 Middlesex Turnpike
		Bedford, MA 01730  USA
		(617) 275-3733
		Fax: (617) 275-4323
		e-mail:  info@dspse.com
		www:  http://www.dspnet.com