Detailed Description

I2S driver implementation for a CC26XX I2S controller.

============================================================================

Limitations

Flash Memory range

The I2S driver is unable to access flash memory in the address range 0x0000 - 0x2000 on devices based on the Cortex M33+ core (CC26X3/CC26X4) due to security constraints.

Supported I2S_MemoryLength values

Only the following memory lengths are supported:

I2S_Params Attributes Limitations

Some attributes in the I2S_Params structure have a limited set of supported values. These limitations are described below:

I2S_Params.samplingFrequency
- The SCK frequency resulting from the selected sampling frequency should be between 47 kHz and 4 MHz.
I2S_Params.isDMAUnused
- Must be false. All transmissions are always performed by the I2S module's own DMA.
I2S_Params.isMSBFirst
- Must be true. All samples are always transmitted MSB first.
I2S_Params.memorySlotLength
- Must be one of the suported I2S_MemoryLength values listed in the above section.
I2S_Params.fixedBufferLength
- Additional restriction: Must be an even multiple of the number of bytes in a frame.

Sample Buffers

This section describes the structure and requirements for the sample buffers used in the I2S_Transaction objects.

Sample words are read from or written to the sample buffers in little-endian byte order, meaning that the least significant byte (LSByte) is stored at the lower byte address, and the most significant byte (MSByte) is stored at the higher byte address.

The sample buffers are divided into frames which are further subdivided into channels, and if a channel is used by both SD0 and SD1 (where the direction of the two pins are the same), then that channel is further subdivided into a sample word for first SD0 and then SD1.

Buffer Size Requirements

The size of the buffers used in I2S_Transaction objects must be an even multiple of the number of bytes per frame. I.e. the number of bytes in the buffers must be of the form: 2*n*k, where k is the size of a frame in bytes and n is an integer satisfying n>=2. 2*n is the number of frames in the buffer.

General Sample Buffer Structure

Below code describes the general structure of a sample buffer if SD0 and SD1 are configured to the same direction.

struct
{
#if SD0_USE_CHANNEL_0 || SD1_USE_CHANNEL_0
    struct
    {
  #if SD0_USE_CHANNEL_0
        uint8_t sd0SampleWord[BYTES_PER_WORD];
  #endif
  #if SD1_USE_CHANNEL_0
        uint8_t sd1SampleWord[BYTES_PER_WORD];
  #endif
    } channel0;
#endif
#if SD0_USE_CHANNEL_1 || SD1_USE_CHANNEL_1
    struct
    {
  #if SD0_USE_CHANNEL_1
        uint8_t sd0SampleWord[BYTES_PER_WORD];
  #endif
  #if SD1_USE_CHANNEL_1
        uint8_t sd1SampleWord[BYTES_PER_WORD];
  #endif
    } channel1;
#endif
// ...
#if SD0_USE_CHANNEL_8 || SD1_USE_CHANNEL_8
    struct
    {
  #if SD0_USE_CHANNEL_8
        uint8_t sd0SampleWord[BYTES_PER_WORD];
  #endif
  #if SD1_USE_CHANNEL_8
        uint8_t sd1SampleWord[BYTES_PER_WORD];
  #endif
    } channel8;
#endif
} sampleBufferFrames[FRAMES_PER_BUFFER];

Notes:

SD0_USE_CHANNEL_n should be true if SD0 uses channel n, otherwise false.
SD1_USE_CHANNEL_n should be true if SD1 uses channel n, otherwise false.
BYTES_PER_WORD is based on the configured memory length:
- I2S_MEMORY_LENGTH_16BITS: 2
- I2S_MEMORY_LENGTH_24BITS: 3
FRAMES_PER_BUFFER must be divisible by 2
sampleBufferFrames needs to be cast to an uint8_t pointer to be used with the I2S driver.

If SD0 and SD1 are not configured to the same direction (or only one is used) then the structure can be simplified as below:

struct
{
#if USE_CHANNEL_0
    uint8_t channel0SampleWord[BYTES_PER_WORD];
#endif
#if USE_CHANNEL_1
    uint8_t channel1SampleWord[BYTES_PER_WORD];
#endif
// ...
#if USE_CHANNEL_8
    uint8_t channel8SampleWord[BYTES_PER_WORD];
#endif
} sampleBufferFrames[FRAMES_PER_BUFFER];

Notes:

USE_CHANNEL_n should be true if channel n is used, otherwise false.

Sample Buffer Structure Example

If for example SD0 and SD1 are configured to the same direction and if channel 0 and 1 are used for SD0 and channel 0 is used for SD1, then the sample buffer would be structured as in the code below.

struct
{
    struct
    {
        uint8_t sd0SampleWord[BYTES_PER_WORD];
        uint8_t sd1SampleWord[BYTES_PER_WORD];
    } channel0;
    struct
    {
        uint8_t sd0SampleWord[BYTES_PER_WORD];
    } channel1;
} sampleBufferFrames[FRAMES_PER_BUFFER];
 // Access LSB of sample 10 of channel 0 on SD1
 uint8_t tmp = sampleBufferFrames[10].channel0.sd1SampleWord[0];

#include <ti/drivers/I2S.h>
#include <ti/drivers/dpl/SemaphoreP.h>
#include <ti/drivers/dpl/HwiP.h>
#include <ti/drivers/Power.h>

Include dependency graph for I2SCC26XX.h:

Go to the source code of this file.

Data Structures
struct	I2SCC26XX_HWAttrs
	I2S Hardware attributes. More...

Typedefs
typedef void(*	I2SCC26XX_PtrUpdate) (I2S_Handle handle, I2SCC26XX_Interface *interface)
	The definition of a function used by the I2S driver to refresh the pointer. More...

Typedef Documentation

§ I2SCC26XX_PtrUpdate

typedef void(* I2SCC26XX_PtrUpdate) (I2S_Handle handle, I2SCC26XX_Interface *interface)

The definition of a function used by the I2S driver to refresh the pointer.

Parameters

I2S_Handle	I2S_Handle
I2SCC26XX_Interface	*interface Pointer on the interface to update