DTMFtonegenerationanddetection：双音多频信号的产生和检测.doc

DTMF tone generation and detection An implementation using the TMS320C54x Gunter Schmer, MTSA SC Group Technical Marketing Rev. 1.0 7/12/96  [The important notice page is required in all application reports. This page is the reverse side of the title page and contains the TI disclaimer and the copyright clause. Always use the latest important notice as provided from the Relational Document Manager (RDM) file. This notice is not typed, changed, corrected, or in any way altered from the RDM file.] abstract This application note describes the implementation of a DTMF tone generator and detector for the TMS320C54x. This application note provides some theoretical background on the algorithms used for tone generation and detection. It documents the actual implementation in detail. Finally the code is benchmarked in terms of its speed and memory requirements. DTMF touch tone dialing: background A DTMF (Dual Tone Multiple Frequency) codec incorporates an encoder that translates key strokes or digit information into dual tone signals, as well as a decoder detecting the presence and the information content of incoming DTMF tone signals. Each key on the keypad is uniquely identified by its row and its column frequency as shown in Figure 1. The DTMF generating and decoding scheme is not too computationally extensive and can easily be handled by a DSP concurrently with other tasks. This article describes an implementation of the DTMF codec on the TMS320C54x, TI’s fixed-point DSP designed especially for telecommunication applications. Figure 1 Touch-tone telephone keypad: A row and a column tone is associated with each digit DTMF tone generator The encoder portion and tone generation part of a DTMF codec is based on two programmable, second order digital sinusoidal oscillators, one for the row the other one for the column tone. Two oscillators instead of eight facilitate the code and reduce the code size. Of course for each digit that is to be encoded, each of the two oscill