5.3. Global Tone Generation (GTG)

• 5.3.1. Global Tone Generation Functions
• 5.3.2. Building and Implementing a Tone Generation Template

Global Tone Generation enables the creation of user-defined tones. The Tone Generation template, TN_GEN, is used to define the tones with the following information:

• Single or dual tone
• Frequency fields
• Amplitude for each frequency
• Duration of tone

5.3.1. Global Tone Generation Functions

The following functions are used to generate tones:

dx_bldtngen( )	build a tone generation template
dx_playtone( )	play a tone

dx_bldtngen( ) is a convenience function that sets up the tone generation template data structure (TN_GEN) by allowing the assignment of specified values to the appropriate fields. The tone generation template is placed in the user's return buffer and can then be used by the dx_playtone( ) function to generate the tone.

dx_playtone( ) plays a tone specified by the tone generation template (pointed to by tngenp). Termination conditions are set using the DV_TPT structure. The reason for termination is returned by the ATDX_TERMMSK( ) function. dx_playtone( ) returns a 0 to indicate that it has completed successfully.

5.3.2. Building and Implementing a Tone Generation Template

The tone generation template defines the frequency, amplitude, and duration of a single or dual frequency tone to be played. You can use the convenience function dx_bldtngen( ) to set up the structure. Use dx_playtone( ) to play the tone.

The TN_GEN data structure is shown below:

typedef struct {  
   unsigned short tg_dflag;        /* dual tone - 1, single tone - 0 */  
   unsigned short tg_freq1;        /* frequency of tone 1 (in Hz) */  
   unsigned short tg_freq2;        /* frequency of tone 2 (in Hz) */  
   short int      tg_ampl1;        /* amplitude of tone 1 (in dB) */  
   short int      tg_ampl2;        /* amplitude of tone 2 (in dB) */  
   short int      tg_dur;          /* duration (in 10 ms) */  
} TN_GEN;

After you build the TN_GEN data structure, there are two ways to define each tone template:

1. Include the values in the structure, or
2. Pass the values to TN_GEN using the dx_bldtngen( ) function.

After defining the template, pass TN_GEN to dx_playtone( ) to play the tone.

If you include the values in the structure, you must create a structure for each tone template. If you pass the values using the dx_playtone( ) function, then you can reuse the structure. If you are only changing one value in a template with many variables, it may be more convenient to use several structures in the code instead of reusing just one.

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