AlgoTron DSP Software for Telecoms & Audio
a TI DSP Third Party Network Member

Home Modems Telephony Audio Utilities Consultancy Glossary Index Contact us

Contact us


Call Waiting Caller ID (Standard) Generator DSP C Code

Description: implements the landline telephony function of Call Waiting Caller IDentity (CWCID) generation. CWCID is sent off-hook in an established call to pass the identity of a third party trying to call one of the talking parties. The talking party can then accept the call by a hook-flash. CWCID is signalled from the exchange - the Generator end - by an alerting dual-tone signal CAS, and acknowledged by the subscriber - the Detector end - with another dual-tone signal ACK. The Caller ID message bytes are then sent by V.23 or Bell 202 modem modulation, formatted as in on-hook Caller ID. The CWCID Generator is for "standard" locales - eg ETSI, UK SIN 227, US Bellcore SDMF/MDMF, Bell Canada - but not for Japan. The software function summary is:

CWCID Generator: sends CAS then, on detecting ACK, sends the Caller ID data - pre-amble, message bytes, checksum - using the on-hook CID encoder routine which selects V.23 or Bell 202. The Generator returns diagnostics, either CWCID completion or the lack of ACK response from the subscriber.

The Generator requires a buffer of the complete message data in parameterised byte form, excluding the checksum byte, to be pre-loaded at the user interface. Message parameterisation in the user code gives flexibility in dealing with Caller ID categories. The message buffer format is 2 per 16-bit word for efficiency in multi-channel use.
         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. Sample rates of 8.0kHz and 9.6kHz can be selected. The function has an initialisation call and a per-sample main routine call, and is re-entrant with memory offset-addressing for multi-channel operation. A comprehensive user's guide is provided with the code.

Processor Load:

Function MIPS# Data memory (words) Prog memory (bytes)#
CWCID-S Generator (+ CID Encoder/Tx) 1.6 5 + (9 + M) x N 1.3k

- #example figures from compiling for the TI TMS320C5000(C55x) DSP processor at 8.0kHz sampling
- in data memory figures M is the user-set buffer size at 2 bytes per word and N is no. of channels

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

Home Modems Telephony Audio Utilities Consultancy Glossary Index Contact us