UART Polling Mode

This sample code guide is designed to help users easily and comprehensively understand UART sample. This sample demonstrates how UART sends and receives data in polling mode. This sample code demonstrates the communication between chip and PC terminal, the chip continuously checks for incoming data within the main program and sends the same data back to the 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_polling_demo();
   

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

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

2. Enter a string on the PC terminal program and send it, and then observe whether the same string is received 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\uart\polling\uart_polling_demo.c.

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)
   {
      Pinmux_Config(UART_TX_PIN, UART0_TX);
      Pinmux_Config(UART_RX_PIN, UART0_RX);
   
      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);
   }
   

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
   RX Trigger Level	UART_InitTypeDef::rxTriggerLevel	UART_RX_FIFO_TRIGGER_LEVEL_14BYTE

Functional Implementation

Send Data

Transmit ### Welcome to use RealTek Bumblebee ###\r\n to the PC terminal:

1. Call UART_SendData() to continuously write data to the TX FIFO. The number of data continuously written to the TX FIFO must not exceed the size of the TX FIFO.

2. Call UART_GetFlagState() to check UART_FLAG_THR_TSR_EMPTY flag state and wait for both TX FIFO and TX shift register to be empty.

3. Repeat the above process to send all data to TX FIFO in batches.

Receive Data

Wait the PC terminal sends a string:

1. Call UART_GetFlagState() to check UART_FLAG_RX_DATA_RDY flag state and wait for RX data to be available.

2. Call UART_ReceiveByte() to read one byte of data from UART RX FIFO.

3. Call UART_SendByte() to send the same data back to the PC terminal.