TDA7318 Beispielcode

Das Ansteuern des TDA7318 ist relativ einfach - wenn man von dem Bitgeschubse absieht. Um an dem IC eine Einstellung zu machen, genügt für jede Funktion ein einziges Byte. Hier der avr-gcc Quellcode für einen AVR Mikrocontroller:

tda7318.h:

#ifndef __I2C__TDA7318_H__INCLUDED__
#define __I2C__TDA7318_H__INCLUDED__

#include <stdint.h>

////////////////////////////////
// Configuration
#ifndef I2C_TDA7318_ADDRESS
#define I2C_TDA7318_ADDRESS 0x44 ///< The chip's address. (Without r/w bit)
#endif
////////////////////////////////

#define I2C_TDA7318_SPEAKER_LF 0x00 ///< Left Front.
#define I2C_TDA7318_SPEAKER_RF 0x01 ///< Right Front.
#define I2C_TDA7318_SPEAKER_LR 0x02 ///< Left Rear. (Just a copy of Left Front)
#define I2C_TDA7318_SPEAKER_RR 0x03 ///< Right Rear. (Just a copy of Right Front)
#define I2C_TDA7318_TONE_BASS 0x00 ///< Bass Control
#define I2C_TDA7318_TONE_TREBLE 0x01 ///< Treble Control

/** \brief Volume Control
 *
 * Sets the volume from 0.00dB to -78.75dB in 1.25dB steps.
 * Only the lower 6 bits are used.
 *
 * @param volume The volume.
 */
void i2c_tda7318_volume_write_begin( uint8_t volume );

/** \brief Speaker Attenuators
 *
 * Speaker attenuation from 0.00dB to 38.75dB in 1.25dB steps. (38.75dB => muted)
 * Only the lower 5 bits are used.
 * To select the speaker, choose one of: I2C_TDA7318_SPEAKER_LF, I2C_TDA7318_SPEAKER_RF, I2C_TDA7318_SPEAKER_LR, I2C_TDA7318_SPEAKER_RR or 0,1,2,3.
 *
 * @param speaker Which speaker to set.
 * @param attenuation Attenuation of selected speaker.
 */
void i2c_tda7318_attenuation_write_begin( uint8_t speaker, uint8_t attenuation );

/** \brief Audio Switch
 *
 * Selects a stereo input and gain from 1 of 4 sources. (only the lower 2 bits are used)
 * Input gain from 18.75dB to 0.00dB in 6.25dB steps. (only the lower 2 bits are used)
 *
 * @param input Which stereo input to choose: 0, 1, 2, 3
 * @param gain Input gain.
 */
void i2c_tda7318_switch_write_begin( uint8_t input, uint8_t gain );

/** \brief Tone Control
 *
 * Sets the Tone from -14dB to 14dB in 2dB steps.
 * Only the lower 4 bits are used.
 *
 * @param tone One of: I2C_TDA7318_TONE_BASS, I2C_TDA7318_TONE_TREBLE or 0, 1.
 * @param volume The volume.
 */
void i2c_tda7318_tone_write_begin( uint8_t tone, uint8_t volume );

#endif

tda7318.c:

#include "i2c.h"
#include "tda7318.h"

void i2c_tda7318_volume_write_begin( uint8_t volume )
{
 volume &= 0x3f;  // clear the first 2 bits -> correct opcode for volume
 // 0 0 v v v v v v
 i2c_writebyte_begin( I2C_TDA7318_ADDRESS << 1, volume );
}

void i2c_tda7318_attenuation_write_begin( uint8_t speaker, uint8_t attenuation )
{
 speaker &= 0x03; // maximum of 4 speakers -> 2 bits
 speaker <<= 5;
 attenuation &= 0x1f; // only 5 bits used for attenuation
 // 1 s s a a a a a
 i2c_writebyte_begin( I2C_TDA7318_ADDRESS << 1, 0x80 | speaker | attenuation );
}

void i2c_tda7318_switch_write_begin( uint8_t input, uint8_t gain )
{
 input &= 0x03;  // there are only 4 sources -> 2 bits needed
 gain &= 0x03;  // 4 steps -> 2 bits
 gain <<= 3;  // now in the correct format
 // 0 1 0 g g 0 i i
 i2c_writebyte_begin( I2C_TDA7318_ADDRESS << 1, 0x40 | input | gain );
}

void i2c_tda7318_tone_write_begin( uint8_t tone, uint8_t volume )
{
 tone &= 0x01;  // only bass and treble -> 1 bit needed
 tone <<= 4;
 volume &= 0x0f;  // 4 bits for volume
 // 0 1 1 t v v v v
 i2c_writebyte_begin( I2C_TDA7318_ADDRESS << 1, 0x60 | tone | volume );
}

Die Einzigen externen Funktionen die noch benötigt werden sind:

void i2c_writebyte_begin( uint8_t address, uint8_t data );

um ein einzelnes Byte an die gegebene I²C Adresse zu schicken, und eventuell

uint8_t i2c_write_end( void );

damit der Schreibvorgang abgeschlossen wird.
Letztendlich sollte man zum Beispiel mit

i2c_tda7318_volume_write_begin( -48 );
i2c_write_end();

Die Lautstärke verändern können.