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DTMF Transmitter DSP C Code

Description: generates digit signals to standard Dual Tone Multi-Frequency (DTMF) telephone format. With DTMF, the 16 possible digits are each signified by pairs of tones, one from a "low" group - 697Hz, 770Hz, 852Hz, 941Hz - and the other from a "high" group - 1209Hz, 1336Hz, 1477Hz, 1633Hz.
         The C code is suitable for any processor with an ANSI-compliant C compiler. It is designed especially for efficient operation on low-cost fixed-point DSP- and general-purpose micro-processors. All data memory is specified as 16-bit integer words. Multiplies are integer 16x16-bit with 32-bit products.
         The software is in the form of four callable subroutines: one sets common-channel default parameters, one initialises per-channel memory, one is for loading each new digit into each digit queue, and one is for per-sample generation. The user is responsible for supplying the codes of digits to be dialled and for accepting each transmit sample. Digits to be dialled can be placed in a queue whose maximum length is programmable.
         To suit applications, the following parameters are made user-programmable: low- and high-tone transmit powers, digit-on timing, digit-off timing. For test purposes, continuous transmission can be set. Sample rates of 8.0kHz or 9.6kHz can be operated. A user's guide is supplied.

Specification: The values PL, PH and Ton, Toff are user-programmable.

Processor Load:

- - #example figures from compiling for the TI TMS320C5000(C55x) DSP processor at 8.0kHz sampling
- *for 16-digit queue

Availability: NOW, sale is under licence - integration support offered