(Page 5 of 5 in this chapter)

8.4 Enabling the Echo Canceller

AG Access includes several DSP files specifically used in conjunction with echo cancellation.
To configure your system for echo cancellation, complete the following steps: Edit the AG configuration file, ag.cfg, by adding the following statement: DspFile = echo.dsp Locate the reference to dtmf.dsp in your ag.cfg file. Change dtmf.dsp to dtmfe.dsp. The modified line should read: DspFile = dtmfe.dsp Save your changes, and restart agmon to re-initialize the board. Set the appropriate AG Access parameters in your application and in your system: To enable echo cancellation with the board's default settings, set the parameter ADI_START_PARMS.echocancel.mode equal to 1. The defaults for each board type are shown in the following table: Board Type Length (msec) Convergence Rate (msec) AG-24 0 0 AG-24+ 4 400 AG-30 0 0 AG-48 0 0 AG-60 0 0 AG-8 2 100 AG-8/80 8 200 AG-T1 4 400 AG-E1 0 0 To enable echo cancellation with specific parameters, set ADI_START_PARMS. echocancel.mode equal to 2. As discussed in Figure 8.3, you may set the ADI_START_PARMS fieldsechocancel.filterlength and echocancel.adapttime to values of your choosing.

(Page 5 of 5 in this chapter)