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Software for Telecoms & Audio
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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 user is responsible for supplying the codes
of digits to be dialled and for accepting each transmit sample. Digits
can be stored in a queue. 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.
To suit applications, the following
parameters are made user-programmable: low- and high-tone transmit powers,
digit-on timing, digit-off timing, digit queue length. For test purposes,
continuous transmission can be set. Sample rates of 8.0kHz or 9.6kHz can
be operated.
Specification: the values PL, PH and Ton, Toff are user-programmable.
| Per-tone power: | PL & PH where PL,PH -3dBm (+6dBm is total peak power) |
| Tone accuracy: | 0.06Hz error |
| Digit on-timing: | Ton \ with granularity in sample-rate periods - max. is 3.5secs. |
| Digit off-timing: | Toff / |
Processor Load:
| MIPS# | Data memory (words) | Prog memory (bytes)# |
| 0.6 | 4(common) + 12*(per channel) | 0.5k |
-
- #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
