Analog Microphone

This example code collects AMIC data and encodes it into PCM voice data using the CODEC.

AMIC collects analog voice data, which is encoded by CODEC and sent to the I2S receive FIFO. The data is then transferred to UART using GDMA.

On the PC side, a serial assistant receives the data transmitted by UART. Audio parsing software is used to analyze the data and play the recorded voice. In this example, the audio parsing software used is Audacity.

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 AMIC module to the EVB, connect MICBIAS to 1.8V, GND to GND, MIC_P to P2_6, and MIC_N to P2_7;

Connect the FT232 module to the EVB to receive UART data, connecting P3_2 to RXD, and P3_3 to TXD.

Building and Downloading

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

Experimental Verification

Preparation Stage

1. Start the PC terminal with PuTTY or UartAssist, use ASCII to receive data, open the UART COM port, and make the following UART settings:

• Baud rate: 3000000

• 8 data bits

• 1 stop bit

• No parity

• No hardware flow control

• Set the output data bytes to redirect to a file.

2. Start the audio parsing software and select the parsing format according to the settings in CODEC. In this example, you can refer to the following Audacity settings.

• Encoding: 16-bit PCM

• Endianness: Little Endian

• Channels: 1 channel

• Sample rate: 1600 Hz

Testing Stage

1. From start to finish of recording, the collected voice data is encoded by CODEC as PCM data and sent to the PC terminal via UART.

2. Use the audio parsing software to view the decoded voice waveform and play the voice.

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\amic\proj

• Source code directory: sdk\samples\peripheral\codec\amic\src

Initialization

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

The initialization process includes initializing the CODEC / UART / I2S / GDMA modules as follows.

1. Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX of the corresponding pins. The I2S pin multiplexing functions are BCLK_SPORT0, LRC_RX_SPORT0, SDI_CODEC_SLAVE, and SDO_CODEC_SLAVE.

   void board_codec_init(void)
   {
      Pad_Config(AMIC_MSBC_CLK_PIN, PAD_SW_MODE, PAD_NOT_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE,PAD_OUT_HIGH);
      Pad_Config(AMIC_MSBC_DAT_PIN, PAD_SW_MODE, PAD_NOT_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE,PAD_OUT_LOW);
   
      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_RX_SPORT0);
      Pinmux_Config(CODEC_TX_PIN,    SDI_CODEC_SLAVE);
      Pinmux_Config(CODEC_RX_PIN,    SDO_CODEC_SLAVE);
   }
   

2. Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX for the UART module corresponding pins.

   void board_uart_init (void)
   {
     Pad_Config(UART_TX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_UP, PAD_OUT_DISABLE, PAD_OUT_HIGH);
     Pad_Config(UART_RX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_UP, PAD_OUT_DISABLE, PAD_OUT_HIGH);
   
     Pinmux_Config(UART_TX_PIN, UART5_TX);
     Pinmux_Config(UART_RX_PIN, UART5_RX);
   }
   

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

I2S 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_Mono
Data Format	I2S_InitTypeDef::I2S_RxDataFormat	I2S_Mode
Data Width	I2S_InitTypeDef::I2S_RxDataWidth	I2S_Width_16Bits

4. Execute UART_StructInit() and UART_Init() to initialize the UART peripheral. Configuration parameters for the UART initialization are as follows:

UART Initialization Parameters

UART Hardware Parameters	Setting in the UART_InitStruct	UART
UART Div	UART_InitTypeDef::UART_Div	1
UART Ovsr	UART_InitTypeDef::UART_Ovsr	8
UART OvsrAdj	UART_InitTypeDef::UART_OvsrAdj	0x492
UART Tx Dma En	UART_InitTypeDef::UART_TxDmaEn	ENABLE
UART Dma En	UART_InitTypeDef::UART_DmaEn	UART_DMA_ENABLE

5. 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_PeripheralToPeripheral
Buffer Size	GDMA_InitTypeDef::GDMA_BufferSize	1000
Source Address Increment or Decrement	GDMA_InitTypeDef::GDMA_SourceInc	DMA_SourceInc_Fix
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_Byte
Source Burst Transaction Length	GDMA_InitTypeDef::GDMA_SourceMsize	GDMA_Msize_4
Destination Burst Transaction Length	GDMA_InitTypeDef::GDMA_DestinationMsize	GDMA_Msize_16
Source Address	GDMA_InitTypeDef::GDMA_SourceAddr	&(I2S1->I2S_RX_FIFO_RD_ADDR)
Destination Address	GDMA_InitTypeDef::GDMA_DestinationAddr	&(UART5->UART_RBR_THR)
Source Handshake	GDMA_InitTypeDef::GDMA_SourceHandshake	GDMA_Handshake_I2S1_TDM0_RX
Destination Handshake	GDMA_InitTypeDef::GDMA_DestHandshake	GDMA_Handshake_UART5_TX

6. Configure the GDMA transfer complete interrupt GDMA_INT_Transfer and NVIC. Related NVIC configuration can be referred to in Interrupt Configuration.

7. 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
Mic Type	CODEC_InitTypeDef::CODEC_Ch0MicType	CODEC_CH_AMIC
MICBST Mode	CODEC_InitTypeDef::CODEC_MicBstMode	MICBST_Mode_Differential
SampleRate	CODEC_InitTypeDef::CODEC_SampleRate0	SAMPLE_RATE_16KHz
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_Rx_DataWidth_16Bits
I2S Channel Sequence	CODEC_InitTypeDef::CODEC_I2SChSequence	CODEC_I2S_CH_L_R

8. Call I2S_Cmd() to enable the I2S receive mode. Call GDMA_Cmd() to enable GDMA transfer.

Functional Implementation

After AMIC collects the voice data, the CODEC module AD conversion puts the voice data into the I2S RX FIFO. The data in the I2S RX FIFO is then transferred to the UART TX FIFO via GDMA. In the serial assistant, save the data sent by UART to a file, and parse the file data using audio parsing software. The data transmission order in each module is shown in the figure below.

Data Transfer Module (AMIC)

1. When the GDMA transfer amount reaches the set BlockSize, it triggers the GDMA_INT_Transfer interrupt. As the audio data undergoes AD conversion via CODEC, the data size is relatively large and a single GDMA transfer cannot meet the demand. The source address, destination address, and BlockSize are reset in the interrupt handler, and GDMA transfer is re-enabled to ensure the transmission of a large amount of data continuously.

   GDMA_SetSourceAddress(GDMA_Channel_AMIC, (uint32_t)(&(I2S0->I2S_RX_FIFO_RD_ADDR)));
   GDMA_SetDestinationAddress(GDMA_Channel_AMIC, (uint32_t)(&(UART5->UART_RBR_THR)));
   
   GDMA_SetBufferSize(GDMA_Channel_AMIC, AUDIO_FRAME_SIZE / 4);
   
   GDMA_ClearINTPendingBit(GDMA_Channel_AMIC_NUM, GDMA_INT_Transfer);
   GDMA_Cmd(GDMA_Channel_AMIC_NUM, ENABLE);