UART TX Data in GDMA Mode

This sample code guide is designed to help users easily and comprehensively understand UART sample. This sample demonstrates how UART sends data in GDMA mode. This sample code demonstrates the communication between chip and PC terminal. Chip transmits some data to PC terminal.

Requirements

For hardware requirements, please refer to the Requirements.

In addition, it is necessary to install serial port assistant tools such as PuTTY or UartAssist on the PC terminal.

Wiring

Connect P3_1 (UART TX Pin) to the RX pin of the FT232 and P3_0 (UART RX Pin) to the TX pin of the FT232.

The hardware connection of UART sample code is shown in the figure below.

UART Sample Code Hardware Connection Diagram

Configurations

1. The following macros can be configured to modify pin definitions.

   • #define UART_TX_PIN         P3_1

   • #define UART_RX_PIN         P3_0

2. The entry function is as follows, call this function in main() to run this sample code. For more details, please refer to the Initialization.

   uart_tx_gdma();
   

Building and Downloading

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

Experimental Verification

Preparation Phase

Start a PC terminal program like PuTTY or UartAssist and connect to the used COM port with the following UART settings:

• Baud rate: 115200.

• 8 data bits.

• 1 stop bit.

• No parity.

• No hardware flow control.

Testing Phase

Press the Reset button on the EVB, chip starts with transmitting ### Welcome to use RealTek Bumblebee ###rn. Observe that the string appears on the PC terminal program.

Code Overview

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

Source Code Directory

• For project directory, please refer to Source Code Directory.

• Source code directory: sdk\src\sample\io_demo\gdma\uart_tx\uart_tx_gdma.c.

UART Initialization

The initialization flow for peripherals can refer to Initialization Flow.

UART initialization flow is shown in the following figure.

UART Initialization Flow Chart

1. Call Pad_Config() and Pinmux_Config() to initialize the pin.

   static void board_uart_init(void)
   {
      Pad_Config(UART_TX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
      Pad_Config(UART_RX_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_UP, PAD_OUT_DISABLE, PAD_OUT_LOW);
   
      Pinmux_Config(UART_TX_PIN, UART0_TX);
      Pinmux_Config(UART_RX_PIN, UART0_RX);
   }
   

2. Call RCC_PeriphClockCmd() to enable the UART clock and function.

3. Initialize the UART peripheral:

   1. Define the UART_InitTypeDef type uartInitStruct, and call UART_StructInit() to pre-fill uartInitStruct with default values.

   2. Modify the uartInitStruct parameters as needed. The UART initialization parameter configuration is shown in the table below.

   3. Call UART_Init() to initialize the UART peripheral.

   UART Initialization Parameters

   UART Hardware Parameters	Setting in the uartInitStruct	UART
   div	UART_InitTypeDef::div	20
   ovsr	UART_InitTypeDef::ovsr	12
   ovsr_adj	UART_InitTypeDef::ovsr_adj	0x252
   Parity Check	UART_InitTypeDef::parity	UART_PARITY_NO_PARTY
   Stop Bit	UART_InitTypeDef::stopBits	UART_STOP_BITS_1
   Data Format	UART_InitTypeDef::wordLen	UART_WROD_LENGTH_8BIT
   Hardware Flow Control	UART_InitTypeDef::autoFlowCtrl	UART_AUTO_FLOW_CTRL_DIS
   GDMA Enable	UART_InitTypeDef::dmaEn	UART_DMA_ENABLE
   TX Waterlevel	UART_InitTypeDef::TxWaterlevel	15
   TX GDMA Enable	UART_InitTypeDef::TxDmaEn	FunctionalState::ENABLE

GDMA Initialization

GDMA initialization flow is shown in the following figure.

GDMA Initialization Flow Chart

1. Call RCC_PeriphClockCmd() to enable the GDMA clock and function.

2. Call GDMA_channel_request to request an unused GDMA channel.

3. Initialize the GDMA peripheral:

   1. Define the GDMA_InitTypeDef type GDMA_InitStruct, and call GDMA_StructInit() to pre-fill GDMA_InitStruct with default values.

   2. Modify the GDMA_InitStruct parameters as needed. The GDMA initialization parameter configuration is shown in the table below.

   3. Call GDMA_Init() to initialize the GDMA peripheral.

   GDMA Initialization Parameters

   GDMA Hardware Parameters	Setting in the GDMA_InitStruct Variables	GDMA
   Channel Num	GDMA_InitTypeDef::GDMA_ChannelNum	UART_TX_DMA_CHANNEL_NUM
   Transfer Direction	GDMA_InitTypeDef::GDMA_DIR	GDMA_DIR_MemoryToPeripheral
   Buffer Size	GDMA_InitTypeDef::GDMA_BufferSize	strLen
   Source Address Increment or Fix	GDMA_InitTypeDef::GDMA_SourceInc	DMA_SourceInc_Inc
   Destination Address Increment or Fix	GDMA_InitTypeDef::GDMA_DestinationInc	DMA_DestinationInc_Fix
   Source Data Size	GDMA_InitTypeDef::GDMA_SourceDataSize	GDMA_DataSize_Byte
   Destination Data Size	GDMA_InitTypeDef::GDMA_DestinationDataSize	GDMA_DataSize_Byte
   Source Burst Transaction Length	GDMA_InitTypeDef::GDMA_SourceMsize	GDMA_Msize_1
   Destination Burst Transaction Length	GDMA_InitTypeDef::GDMA_DestinationMsize	GDMA_Msize_1
   Source Address	GDMA_InitTypeDef::GDMA_SourceAddr	(uint32_t)(GDMA_SendBuffer)
   Destination Address	GDMA_InitTypeDef::GDMA_DestinationAddr	(uint32_t)(&(UART->RB_THR))
   Destination Handshake	GDMA_InitTypeDef::GDMA_DestHandshake	GDMA_Handshake_UART0_TX

4. Call NVIC_Init() to enable NVIC of GDMA.

5. Call GDMA_INTConfig() to enable GDMA transfer complete interrupt GDMA_INT_Transfer.

6. Call GDMA_Cmd() to enable GDMA.

Functional Implementation

GDMA Interrupt Handle

When GDMA transfer completion to the destination, GDMA_INT_Transfer interrupt is triggered:

1. Call GDMA_ClearINTPendingBit() to clear GDMA_INT_Transfer interrupt.