Example Summary

Example that uses the I2S driver to echo the audio received from the Line In (Audio source) over the Line Out (headphones|speakers). This example shows:

• How to initialize the I2S driver in streaming mode with audio echo.
• How to achieve I2S transfers with CD quality (16bits - 44.1 kHz).
• How to treat (filter) sample data.

Peripherals & Pin Assignments

When this project is built, the SysConfig tool will generate the TI-Driver configurations into the ti_drivers_config.c and ti_drivers_config.h files. Information on pins and resources used is present in both generated files. Additionally, the System Configuration file (*.syscfg) present in the project may be opened with SysConfig’s graphical user interface to determine pins and resources used.

• CONFIG_GPIO_LED_0 - Indicates that the board was initialized within mainThread().
• CONFIG_I2C_0 - Used to configure the TI codec on the Audio BoosterPack.
• CONFIG_I2S_0 - Used to echo sounds received from Audio In on Audio Out.

BoosterPacks, Board Resources & Jumper Settings

This example requires a CC3200 Audio BoosterPack

For board specific jumper settings, resources and BoosterPack modifications, refer to the Board.html file. Due to the required jumper wires, some boards will not use the CC3200AUDBOOST hardware component in SysConfig but will instead assign the I2S pins manually.

If you’re using an IDE such as Code Composer Studio (CCS) or IAR, please refer to Board.html in your project directory for resources used and board-specific jumper settings.

The Board.html can also be found in your SDK installation:

<SDK_INSTALL_DIR>/source/ti/boards/<BOARD>

• A pair of (headphones|speakers) and an audio source (smartphone) are required to observe functionality.

Example Usage

• Mount the CC3200 Audio BoosterPack.

• Connect headphones or speakers to the Audio BoosterPack, as well as an audio source.

• Run the example. CONFIG_GPIO_LED_0 turns ON to indicate driver initialization is complete.

• Sounds captured on audio line in are echoed after basic filtering.

• The quality of the audio output is directly related to the quality of your audio source. For this purpose, avoid using a highly disturbed audio source. For example, when using your smartphone as an audio source, avoid leaving it in charge at the same time: this creates a lot of audio disturbances.

If you halt the target during execution of this example, and then run again, the echoing will not resume. You will need to reload the program.

Application Design Details

• One thread, echoThread is used to configure the codec and start the I2S transfers.

• Ten I2S_Transactions are declared and a buffer is associated to each of them (in this example, the buffer held by a transaction remains the same during execution).

• The I2S transactions are initially queued in two lists: i2sReadList and i2sWriteList. treatmentList will be populated later (i.e. when some transaction of the i2sReadList will be finished).

• The buffers held by the transactions are successively written (by the read interface), treated and sent out (by the write interface). Here is a scheme showing the path followed by a transaction:

    `i2sReadList`          `treatmentList`          `i2sWriteList`
    [Transaction] ... (1)   [Transaction] ... (2)   [Transaction]....  (3)
    [Transaction]   :......>[Transaction]   :       [Transaction]   :
    [Transaction]                           :       [Transaction]   :
 ..>[Transaction]                           :......>[Transaction]   :
 :                                                                  :
 :..................................................................:

(1) The read interface systematically fills the buffer contained in the head transaction of the i2sReadList. When the buffer held by this transaction is full, the transaction is dequeued from the i2sReadList and queued as the tail of the treatmentList. The read interface continues receiving data by using the next transaction of the i2sReadList.

(2) The treatment function treats the sample data contained by the transactions queued in the treatmentList. The transaction treated is the head transaction of the treatmentList. Once this transaction is treated, the transaction is dequeued from the treatmentList and queued in the i2sWriteList.

(3) The write interface systematically sends out the buffer contained in the head transaction of the i2sWriteList. When the buffer held by this transaction has been completely sent out, the corresponding transaction is dequeued from the i2sWriteList and queued in the i2sReadList . The write interface continues sending out data by using the next transaction of the i2sWriteList.

The drivers by default are non-instrumented in order to limit code size.

FreeRTOS:

• Please view the FreeRTOSConfig.h header file for example configuration information.