Audio level controls

Macros
#define	DEFAULT_DAC_LEVEL   0.0
#define	DEFAULT_ADC_LEVEL   -6.0
#define	DEFAULT_PGA_GAIN   16
#define	DEFAULT_HP_LEVEL   -6.0

Functions
int	Bela_setDACLevel (float decibels)
	Set the level of the audio DAC. More...
int	Bela_setADCLevel (float decibels)
	Set the level of the audio ADC. More...
int	Bela_setPgaGain (float decibels, int channel)
	Set the gain of the audio preamplifier. More...
int	Bela_setHeadphoneLevel (float decibels)
	Set the level of the onboard headphone amplifier. More...
int	Bela_muteSpeakers (int mute)
	Mute or unmute the onboard speaker amplifiers. More...

Detailed Description

These functions control the input and output levels for the audio codec. If a Bela program does not call these functions, sensible default levels will be used.

Macro Definition Documentation

#define DEFAULT_DAC_LEVEL   0.0

Default level of the audio DAC in decibels. See Bela_setDACLevel().

#define DEFAULT_ADC_LEVEL   -6.0

Default level of the audio ADC in decibels. See Bela_setADCLevel().

#define DEFAULT_PGA_GAIN   16

Default level of the Programmable Gain Amplifier in decibels.

#define DEFAULT_HP_LEVEL   -6.0

Default level of the headphone output in decibels. See Bela_setHeadphoneLevel().

Function Documentation

int Bela_setDACLevel

(

float

decibels

)

Set the level of the audio DAC.

This function sets the level of all audio outputs (headphone, line, speaker). It does not affect the level of the (non-audio) analog outputs.

Important: do not call this function from within render(), as it does not make any guarantees on real-time performance.

Parameters

decibels

Level of the DAC output. Valid levels range from -63.5 (lowest) to 0 (highest) in steps of 0.5dB. Levels between increments of 0.5 will be rounded down.

Returns

0 on success, or nonzero if an error occurred.

int Bela_setADCLevel

(

float

decibels

)

Set the level of the audio ADC.

This function sets the level of the audio input. It does not affect the level of the (non-audio) analog inputs.

Important: do not call this function from within render(), as it does not make any guarantees on real-time performance.

Parameters

decibels

Level of the ADC input. Valid levels range from -12 (lowest) to 0 (highest) in steps of 1.5dB. Levels between increments of 1.5 will be rounded down.

Returns

0 on success, or nonzero if an error occurred.

int Bela_setPgaGain	(	float	decibels,
		int	channel
	)

Set the gain of the audio preamplifier.

This function sets the level of the Programmable Gain Amplifier(PGA), which amplifies the signal before the ADC.

Important: do not call this function from within render(), as it does not make any guarantees on real-time performance.

Parameters

decibels	Level of the PGA Valid levels range from 0 (lowest) to 59.5 (highest) in steps of 0.5dB. Levels between increments of 0.5 will be rounded.
channel	Specifies which channel to apply the gain to. Channel 0 is left, channel 1 is right

Returns

0 on success, or nonzero if an error occurred.

int Bela_setHeadphoneLevel

(

float

decibels

)

Set the level of the onboard headphone amplifier.

This function sets the level of the headphone output only (3-pin connector on the Bela cape or the output jack on the BeagleBone Audio Cape). It does not affect the level of the speakers or the line out pads on the cape.

Important: do not call this function from within render(), as it does not make any guarantees on real-time performance.

Parameters

decibels

Level of the DAC output. Valid levels range from -63.5 (lowest) to 0 (highest) in steps of 0.5dB. Levels between increments of 0.5 will be rounded down.

Returns

0 on success, or nonzero if an error occurred.

int Bela_muteSpeakers

(

int

mute

)

Mute or unmute the onboard speaker amplifiers.

This function mutes or unmutes the amplifiers on the Bela cape. Whether the speakers begin muted or unmuted depends on the BelaInitSettings structure passed to Bela_initAudio().

Important: do not call this function from within render(), as it does not make any guarantees on real-time performance.

Parameters

mute	0 to enable the speakers, nonzero to mute the speakers.

Returns

0 on success, or nonzero if an error occurred.