Tx Polling

This example demonstrates the data transmission function using the I2S peripheral in polling mode.

Connect the I2S TX pin to the Logic Analyzer to observe the waveform of the transmitted data.

Requirements

For requirements, please refer to the Requirements.

Wiring

Connect P3_2, P3_3, and P4_0 on the EVB to a Logic Analyzer.

P3_2 is LRCK, P3_3 is BCLK, and P4_0 is DATA.

Building and Downloading

For building and downloading, please refer to the Building and Downloading.

Experimental Verification

After the EVB starts, observe the I2S output waveform using a Logic Analyzer. The I2S output waveform is shown in the following figure.

Here should be I2S output waveform — I2S output waveform

Code Overview

This section introduces the code and process description for initialization and corresponding function implementation in the sample.

Source Code Directory

The directory for project file and source code are as follows:

Project directory: sdk\samples\peripheral\i2s\tx_polling\proj
Source code directory: sdk\samples\peripheral\i2s\tx_polling\src

Initialization

The initialization flow for peripherals can refer to Initialization Flow in General Introduction.

Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX of the corresponding pins.

void board_i2s_init(void)
{
   Pad_Config(I2S_BCLK_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);
   Pad_Config(I2S_LRCK_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);
   Pad_Config(I2S_DATA_TX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_LOW);

   Pinmux_Config(I2S_BCLK_PIN, I2S_BCLK_PINMUX);
   Pinmux_Config(I2S_LRCK_PIN, I2S_LRCK_PINMUX);
   Pinmux_Config(I2S_DATA_TX_PIN, I2S_DATA_TX_PINMUX);
}

Call RCC_PeriphClockCmd() to enable the I2S clock.
Initialize the I2S peripheral:
1. Define a I2S_InitTypeDef type I2S_InitStruct, call I2S_StructInit() to pre-fill I2S_InitStruct with default values.
2. Modify the parameters of I2S_InitStruct as required. The initialization parameter configuration for I2S is shown in the table below.
3. Call I2S_Init() to initialize the I2S peripheral.

I2S Initialization Parameters
I2S Hardware Parameters	Setting in the `I2S_InitStruct`	I2S
Clock Source	`I2S_InitTypeDef::I2S_ClockSource`	`I2S_CLK_40M`
Sample Rate (Mi)	`I2S_InitTypeDef::I2S_TxBClockMi`	0x271
Sample Rate (Ni)	`I2S_InitTypeDef::I2S_TxBClockNi`	0x10
Device Mode	`I2S_InitTypeDef::I2S_DeviceMode`	`I2S_DeviceMode_Master`
Channel Type	`I2S_InitTypeDef::I2S_TxChannelType`	`I2S_Channel_stereo`
Data Width	`I2S_InitTypeDef::I2S_TxDataWidth`	`I2S_Width_16Bits`
Data Format	`I2S_InitTypeDef::I2S_TxDataFormat`	`I2S_Mode`

Enable the I2S TX function.
```
I2S_Cmd(I2S_NUM, I2S_MODE_TX, ENABLE);
```

Functional Implementation

Define the data to be sent, and use I2S_SendData() to continuously send the data. The data sent by I2S can be observed in the Logic Analyzer.

void i2s_senddata(void)
{
    uint32_t i = 0x12348800;

    while (1)
    {
        if (I2S_GetTxFIFOFreeLen(I2S_NUM))
        {
            /* 16bit format, lower half word send first! */
            I2S_SendData(I2S_NUM, i++);
        }
    }
}