dx_listenecrex( )

Cautions | Example | Errors | See Also

Parameter	Description
chdev	Specifies the voice channel device handle obtained when the channel was opened using dx_open( ).
sc_tsinfop	Specifies a pointer to the data structure SC_TSINFO.

NOTE:

For this function, NLP is enabled by default. If you do not want NLP enabled, use dx_listenecrex( ) with NLP disabled.

The SC_TSINFO structure is declared as follows:

typedef struct sc_tsinfo {  
        unsigned long    sc_numts;  
        long             *sc_tsarrayp;  
} SC_TSINFO;

The sc_numts field of the SC_TSINFO structure must be set to 1. The sc_tsarrayp field of the SC_TSINFO structure must be initialized with a pointer to a valid array. The first element of this array must contain a valid SCbus time-slot number (between 0 and 1023) which was obtained by issuing a call to xx_getxmitslot( ) (where xx_ is ag_, dt_, dx_, or ms_) or dx_getxmitslotecr( ), depending on the application of the function. Upon return from the dx_listenecr( ) function, the echo canceller of the specified voice channel is connected to the SCbus time slot specified, and it uses the signal carried on the SCbus time slot as the echo-reference signal for echo cancellation.

Cautions

This function fails when:

• An invalid channel device handle is specified.
• An invalid SCbus time-slot number is specified.
• The ECR feature is not enabled on the board specified.
• The ECR feature is not supported on the board specified.

Example

#include <stdio.h>

#include <windows.h>  
#include <srllib.h>  
#include <dxxxlib.h>  
#include <msilib.h>  
main()  
{  
   int msdev1, chdev2;        /* MSI/SC Station, and Voice Channel device handles */  
   SC_TSINFO  sc_tsinfo;         /* Time slot information structure */  
   long scts;                 /* SCbus time slot */  
   
   /* Open MSI/SC board 1 station 1 device */  
   if ((msdev1 = ms_open("msiB1C1", 0)) == -1) {  
       /* Perform system error processing */  
       exit(1);  
   }  
   
   /* Open board 1 channel 2 device */  
   if ((chdev2 = dx_open("dxxxB1C2", 0)) == -1) {  
       /* Perform system error processing */  
       exit(1);  
   }  
   
   /* Fill in the SCbus time slot information */  
   sc_tsinfo.sc_numts = 1;  
   sc_tsinfo.sc_tsarrayp = &scts;  
   
   /* Get SCbus time slot connected to transmit of MSI/SC station 1 on board 1 */  
   if (ms_getxmitslot(msdev1, &sc_tsinfo) == -1) {  
       printf("Error message = %s", ATDV_ERRMSGP(msdev1));  
       exit(1);  
   }  
   
   /* Connect the echo-reference receive of voice channel 2 on board 1 to   
   
      the transmit signal of msdev1 */   
   if (dx_listenecr(chdev2, &sc_tsinfo) == -1) {  
       printf("Error message = %s", ATDV_ERRMSGP(chdev2));  
       exit(1);  
   }  
   /* Continue  
   .  
   .  
   .  
   /* Then perform xx_unlisten()s and dx_unlistenecr(), plus all xx_close()s */  
     return(0);  
}

Errors

If the function returns -1, use the SRL Standard Attribute function ATDV_LASTERR( ) to obtain the error code or use ATDV_ERRMSGP( ) to obtain a descriptive error message. One of the following error codes may be returned:

Equate	Returned When
EDX_BADPARM	Parameter error
EDX_SH_BADCMD	Function is not supported in current bus configuration
EDX_SH_BADEXTTS	SCbus time slot is not supported at current clock rate
EDX_SH_BADINDX	Invalid Switch Handler index number
EDX_SH_BADLCLTS	Invalid channel number
EDX_SH_BADMODE	Function not supported in current bus configuration
EDX_SH_CMDBLOCK	Blocking function is in progress
EDX_SH_LCLTSCNCT	Channel is already connected to SCbus
EDX_SH_LIBBSY	Switch Handler library busy
EDX_SH_LIBNOTINIT	Switch Handler library uninitialized
EDX_SH_MISSING	Switch Handler is not present
EDX_SH_NOCLK	Switch Handler clock fallback failed
EDX_SYSTEM	Error from operating system; use dx_fileerrno( ) to obtain error value

See Also

• dx_getxmitslotecr( )
• dx_listen( )
• dx_listenecrex( )
• dx_unlistenecr( )
• xx_getxmitslot( )

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