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DTMF Transmit Software for Texas TMS320C54x/C55x & C2xx/C5x DSPs

This software generates digit signals to standard Dual Tone Multi-Frequency (DTMF) telephone format. With DTMF, the 16 possible digits are each is 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 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 processing. Sample rates of 8.0kHz or 9.6kHz can be set. 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 of any preset maximum length.

The following parameters are user-programmable: low- and high-tone transmit powers, digit-on timing, digit-off timing. For test purposes, continuous transmission can be set. The software can be operated in a multi-channel mode: a pointer is set to each per-channel block of memory at each sub-routine call. By making multiple sub-routine calls, the code can also be operated on blocks of samples.

Specification: the values Pl,Ph and Ton,Toff are user-programmable

• Per-tone power: Pl & Ph (each =< -3dBm for full-scale = +6dBm)

• Tone accuracy: <0.06Hz error

• Digit on-timing: Ton \ with granularity in sample-rate periods

• Digit off-timing: Toff / up to >3secs. duration

DSP Load: (*for 16-digit queue)

• MIPS: 0.23 - 8.0kHz sampling ; 0.28 - 9.6kHz sampling

• Data memory: 4(common)+12*(per channel) words

• Program memory: 0.15k words

Availability: NOW, with user's guide - integration support can be provided