i2s_at91.h File Reference

I2S driver functions. More...

#include <cfg/compiler.h>
#include <cfg/macros.h>
#include <io/arm.h>

Go to the source code of this file.

Defines
#define	I2S_FIRST_BUF   0
	First buffer.
#define	I2S_SECOND_BUF   1
	Second buffer.
Functions
void	i2s_init (void)
	Initializes the module and sets current buffer to I2S_FIRST_BUF.
uint8_t *	i2s_getBuffer (unsigned buf_num)
	Returns one of the two buffers or NULL if none is available.
uint8_t *	i2s_getFreeBuffer (void)
	Returns a buffer that will be played after the current one.
bool	i2s_start (void)
	Starts playing from I2S_FIRST_BUFFER.

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Detailed Description

I2S driver functions.

This driver uses a double buffering technique to keep i2s bus busy. First fill in the two buffers using i2s_getBuffer(), then start audio playing with i2s_start(). Then call i2s_getFreeBuffer() until you have finished your samples. The reproduction will automatically stop if you don't call i2s_getFreeBuffer() frequently enough.

Example:

 // fill in the buffers before start
 buf = i2s_getBuffer(I2S_FIRST_BUF);
 // ...
 buf = i2s_getBuffer(I2S_SECOND_BUF);
 // ...
 // here the driver will play only the first two buffers...
 i2s_start();
 // ...call getFreeBuffer() to continue playing.
 while (!(buf = i2s_getFreeBuffer()))
     ;
 // now fill the buffer again

Author:

Luca Ottaviano <lottaviano@develer.com>

Definition in file i2s_at91.h.

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Function Documentation

uint8_t* i2s_getBuffer

(

unsigned

buf_num

)

Returns one of the two buffers or NULL if none is available.

You can't call this function if you have already started the player.

Parameters:

buf_num

The number of the buffer, ie I2S_FIRST_BUF or I2S_SECOND_BUF.

Returns:

A pointer to the buffer if the buffer is available (not full), 0 on errors

Definition at line 69 of file i2s_at91.c.

uint8_t* i2s_getFreeBuffer

(

void

)

Returns a buffer that will be played after the current one.

You should fill it faster than your reproduction time. You can't call this function if the player is not running

Returns:

The next buffer to be played, 0 if both are busy.

Definition at line 87 of file i2s_at91.c.

bool i2s_start

(

void

)

Starts playing from I2S_FIRST_BUFFER.

You must have filled both buffers before calling this function. Does nothing if already playing.

Returns:

false on errors, true otherwise.

Definition at line 121 of file i2s_at91.c.