Playback

This example demonstrates how to encode a 1KHz sine wave signal via CODEC and output audio.

It uses GDMA to transfer I2S data from memory to the I2S transmit FIFO, then encodes it into PDM signals using CODEC.

External PDM players can play fixed-frequency sine wave audio.

Requirements

For requirements, please refer to the Requirements.

In addition, you need to install PuTTY or UartAssist serial assistant tools and audio parsing tools like Audacity on the PC terminal.

Wiring

Connect the external PDM player to the EVB, connecting P4_3 to CLK and P4_2 to DATA.

Building and Downloading

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

Experimental Verification

Listen to the 1KHz sine wave sound through the PDM player.

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\codec\playback\proj
Source code directory: sdk\samples\peripheral\codec\playback\src

Initialization

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

The initialization process includes initializing the codec, uart, i2s, and gdma modules as follows.

Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX for PDM-related pins.

void board_codec_init(void)
{
    Pad_Config(PDM_CLK_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);
    Pad_Config(PDM_DAT_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);

    Pinmux_Config(PDM_CLK_PIN, PDM_CLK);
    Pinmux_Config(PDM_DAT_PIN, PDM_DATA);
}

Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX for I2S-related pins.

void board_i2s_init(void)
{
    Pad_Config(CODEC_BCLK_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);
    Pad_Config(CODEC_LRCLK_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,PAD_OUT_LOW);
    Pad_Config(CODEC_TX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);
    Pad_Config(CODEC_RX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_LOW);

    Pinmux_Config(CODEC_BCLK_PIN, BCLK_SPORT0);
    Pinmux_Config(CODEC_LRCLK_PIN, LRC_SPORT0);
    Pinmux_Config(CODEC_TX_PIN,  DACDAT_SPORT0);
}

Execute I2S_StructInit() and I2S_Init() to initialize the I2S peripheral. Configuration parameters for the I2S0 initialization are as follows:

I2S master RX initialization parameters
I2S Hardware Parameters	Setting in the `I2S_InitStruct`	I2S master RX
Sample Rate (Mi)	`I2S_InitTypeDef::I2S_RxBClockMi`	0x271
Sample Rate (Ni)	`I2S_InitTypeDef::I2S_RxBClockNi`	0x10
Device Mode	`I2S_InitTypeDef::I2S_DeviceMode`	`I2S_DeviceMode_Master`
Channel Type	`I2S_InitTypeDef::I2S_RxChannelType`	`I2S_Channel_stereo`
Data Format	`I2S_InitTypeDef::I2S_RxDataFormat`	`I2S_Mode`
Data Width	`I2S_InitTypeDef::I2S_RxDataWidth`	`I2S_Width_24Bits`

Execute GDMA_StructInit() and GDMA_Init() to initialize the GDMA peripheral. Configuration parameters for the GDMA initialization are as follows:

GDMA initialization parameters
GDMA Hardware Parameters	Setting in the `GDMA_InitStruct`	GDMA Channel
Channel Num	`GDMA_InitTypeDef::GDMA_ChannelNum`	0
Transfer Direction	`GDMA_InitTypeDef::GDMA_DIR`	`GDMA_DIR_MemoryToPeripheral`
Source Address Increment or Decrement	`GDMA_InitTypeDef::GDMA_SourceInc`	`DMA_SourceInc_Inc`
Destination Address Increment or Decrement	`GDMA_InitTypeDef::GDMA_DestinationInc`	`DMA_DestinationInc_Fix`
Source Data Size	`GDMA_InitTypeDef::GDMA_SourceDataSize`	`GDMA_DataSize_Word`
Destination Data Size	`GDMA_InitTypeDef::GDMA_DestinationDataSize`	`GDMA_DataSize_Word`
Source Burst Transaction Length	`GDMA_InitTypeDef::GDMA_SourceMsize`	`GDMA_Msize_4`
Destination Burst Transaction Length	`GDMA_InitTypeDef::GDMA_DestinationMsize`	`GDMA_Msize_4`
Source Address	`GDMA_InitTypeDef::GDMA_SourceAddr`	`codec_drv_cos_table`
Destination Address	`GDMA_InitTypeDef::GDMA_DestinationAddr`	`&(I2S0->I2S_TX_FIFO_WR_ADDR)`
Destination Handshake	`GDMA_InitTypeDef::GDMA_DestHandshake`	`GDMA_Handshake_I2S0_TDM0_TX`

Configure the GDMA transfer complete interrupt GDMA_INT_Transfer and NVIC. Related NVIC configuration can be referred to in 中断配置.
Initialize the CODEC peripheral.
1. Call CODEC_AnalogCircuitInit() to initialize the analog circuit.
2. Call RCC_PeriphClockCmd() to enable the CODEC clock.
3. Execute CODEC_StructInit() and CODEC_Init() to initialize the CODEC peripheral. Configuration parameters for the CODEC initialization are as follows:

CODEC initialization parameters
CODEC Hardware Parameters	Setting in the `CODEC_InitStruct`	CODEC
Da Mute	`CODEC_InitTypeDef::CODEC_DaMute`	`CODEC_UNMUTE`
Da Gain Mode	`CODEC_InitTypeDef::CODEC_DaGain`	0xAF
DaC Dither	`CODEC_InitTypeDef::CODEC_DaC_Dither`	`DAC_DA_DITHER_DISABLE`
I2S Data Format	`CODEC_InitTypeDef::CODEC_I2SFormat`	`CODEC_I2S_DataFormat_I2S`
I2S Channel Len	`CODEC_InitTypeDef::CODEC_I2SChannelLen`	`I2S_CHANNELLEN_32`
I2S Data Width	`CODEC_InitTypeDef::CODEC_I2SRxDataWidth`	`CODEC_I2S_Tx_DataWidth_24Bits`
I2S Channel Sequence	`CODEC_InitTypeDef::CODEC_I2SChSequence`	`CODEC_I2S_CH_L_R`

Execute preload_cos_table to prepare the sine wave data to be sent.
Call I2S_Cmd() to enable the I2S receive mode. Call GDMA_Cmd() to enable GDMA transfer.

Functional Implementation

The sine wave data is transferred by GDMA from memory to the I2S TX FIFO. After being converted by DA (Digital-to-Analog) module in CODEC, the audio can be heard through an external PDM amplifier. The data transmission order across each module is illustrated in the diagram below.

this should be PLAYBACK waveform — data transfer module

When the GDMA transfer amount reaches the set BlockSize, it triggers the GDMA_INT_Transfer interrupt. In the interrupt handler, the source address, destination address, and BlockSize are reset, and GDMA transfer is re-enabled to ensure continuous data transmission.

GDMA_SetSourceAddress(CODEC_GDMA_Channel, (uint32_t)codec_drv_cos_table);
GDMA_SetDestinationAddress(CODEC_GDMA_Channel, (uint32_t)(&(I2S0->I2S_TX_FIFO_WR_ADDR)));
GDMA_SetBufferSize(CODEC_GDMA_Channel, CODEC_DRV_COS_TABLE_SAMPLE);
GDMA_ClearINTPendingBit(CODEC_GDMA_Channel_NUM, GDMA_INT_Transfer);
GDMA_Cmd(CODEC_GDMA_Channel_NUM, ENABLE);