Welcome to STM32-BoardCar repository

4. Serial communication (UASRT)

Serial communication

Serial communication1. Software-Hardware2. Brief principle1. Hardware schematic diagram2. Physical connection diagram3. Control principle3. Project configuration1. Description2. Pin configuration4. Main functions1. User function2. LL library function analysis5. Experimental phenomena

This tutorial demonstrates: sending and printing serial port information through serial port (USART1) interrupt.

1. Software-Hardware

STM32F103CubeIDE
STM32 Robot Development Board
USART: chip internal peripherals
Type-C data cable or ST-Link
Download programs or simulate the development board

2. Brief principle

1. Hardware schematic diagram

2. Physical connection diagram

USART1 on the development board leads to two interfaces: Type-C and USART1;

It is recommended to use the Type-C burning interface for testing and sending and receiving serial port information.

USART (schematic name)	pin	Function
USART1_TX	PA9	USART1 sends data
USART1_RX	PA10	USART1 receives data

3. Control principle

Send data to the serial port (USART1) through the serial port debugging assistant to trigger the serial port interrupt, and print out the data through the serial port interrupt callback function.

Computer Communications
Classified by data transmission method: serial communication and parallel communication
- Serial Communication: Data is transferred bit by bit

Parallel communication: Multiple bits of data are transmitted simultaneously

Serial Communication
- Serial communication data synchronization mode: synchronous serial communication and asynchronous serial communication
Synchronous serial communication: The sender and receiver rely on independent clock lines to synchronize signals.
Asynchronous serial communication: The sending and receiving parties complete communication according to the agreed character format and communication rate.
- Serial communication data transmission direction: single duplex, half duplex and full duplex.

Simplex: Data can only be transmitted in one direction, and cannot be sent and received at the same time;

Half-duplex: Data is transmitted in both directions, but cannot be sent and received at the same time;

Full Duplex: Data can be transmitted in both directions at the same time, and can be sent and received at the same time.

USART(Universal Synchronous/Asynchronous Receiver/Transmitter)

USART supports synchronous and asynchronous communication. Our tutorial uses UART (Universal Serial Asynchronous Receiver-Transmitter).

Asynchronous serial communication
- Communication Rate
  Baud rate: The number of binary digits transmitted per second, in bit/s (bps).


Commonly used baud rates: 9600, 57600 and 115200
Baud rate 115200: 115200 bits transmitted per second

Character format


xxxxxxxxxx
When transmitting data, the low bit comes first and the high bit comes last.

Data frame format: Start bit + data bit + check bit + stop bit

Start bit (beginning of data frame): 1 bit

Data bits: 5~8 bits

Check digit: odd or even parity (whether the number of "1"s in the data is odd or even)

Stop bit (end of data frame): 0.5, 1.5, 2 stop bits

USART two-way communication

USART (development board)	Peripheral/USB to TTL module
TXD	RXD
RXD	TXD
GND	GND
VCC	VCC
Precautions	1.TXD (transmitting line): pin used to transmit data 2.RXD (receiving line): pin used to receive data 3.GND (ground wire): used to connect to ground pins to ensure that the system level is consistent; 4.VCC (power line): If the peripherals do not have independent power supply, the VCC pin needs to be correctly connected to the appropriate power supply voltage; 5.USART two-way communication requires at least two pins: TXD (transmitting line) and RXD (receiving line).

Common serial port character format configuration: 1 start bit, 8 data bits, no parity, 1 stop bit

3. Project configuration

Project configuration: Prompt configuration options during STM32CubeIDE project configuration

1. Description

Omitted project configuration part: New project, chip selection, project configuration, SYS of pin configuration, RCC configuration, clock configuration and project configuration content

The project configuration part that is not omitted is the key point that needs to be configured in this tutorial.


xxxxxxxxxx
Please refer to [2. Development environment construction and use: STM32CubeIDE installation and use] to understand how to configure the omitted parts of the project.

2. Pin configuration

Configure specified pin function

You can directly select the corresponding pin number in the pin view, and the corresponding options will appear when you left-click the mouse.

USART

NVIC

Later, when it comes to modifying the interrupt priority, you need to enter the NVIC interface settings. The default priority is used here.

Advanced Settings

Generate code

4. Main functions

It mainly introduces the functional code written by the user. For detailed code, you can open the project file provided by us yourself and enter the Bsp folder to view the source code.

1. User function

function：USART1_DataByte

function prototype	void USART1_DataByte(uint8_t data_byte)
function description	Send a byte
Input parameters	data_byte：data
return value	none

function：USART1_DataString

function prototype	void USART1_DataString(uint8_t *data_str, uint16_t datasize)
function description	send a string
Input parameters 1	data_str: data first address
Input parameters 2	datasize: Number of bytes of data
return value	none

2. LL library function analysis

The HAL library functions that have been introduced in the previous tutorial will not be introduced again in the tutorial!


xxxxxxxxxx
If you want to find the HAL library and LL library function analysis involved in the entire tutorial, you can view the documents in the folder [8. STM32 Manual: STM32F1_HAL Library and LL Library_User Manual]

function: LL_USART_Init

function prototype	ErrorStatus LL_USART_Init(USART_TypeDef USARTx, const* LL_USART_InitTypeDef *USART_InitStruct)
function description	Initialize USART peripheral
Input parameters 1	USARTx：USARTx handle address
Input parameters 2	USART_InitStruct: USART initialization structure, containing configuration information of the specified USART peripherals
return value	ErrorStatus：SUCCESS、ERROR

function：LL_USART_ConfigAsyncMode

function prototype	void LL_USART_ConfigAsyncMode(USART_TypeDef *USARTx)
function description	Configure the specified USART peripheral to asynchronous mode
Input parameters	USARTx：USARTx handle address
return value	none

function：LL_USART_Enable

function prototype	void LL_USART_Enable(USART_TypeDef *USARTx)
function description	Enable specified USART peripheral
Input parameters	USARTx：USARTx handle address
return value	none

function：LL_USART_ReceiveData8

function prototype	uint8_t LL_USART_ReceiveData8(const USART_TypeDef *USARTx)
function description	Specify the USART peripheral to receive 8-bit data
Input parameters	USARTx：USARTx handle address
return value	received data

function：LL_USART_TransmitData8

function prototype	void LL_USART_TransmitData8(USART_TypeDef *USARTx, uint8_t Value)
function description	Specify the USART peripheral to send 8-bit data
Input parameters 1	USARTx：USARTx handle address
Input parameters 2	Value: sent data
return value	none

function：LL_USART_IsActiveFlag_TXE

function prototype	uint32_t LL_USART_IsActiveFlag_TXE(const USART_TypeDef *USARTx)
function description	Check the TXE flag status of the specified USART peripheral
Input parameters	USARTx：USARTx handle address
return value	0 (inactive), 1 (active)

function：LL_USART_EnableIT_RXNE

function prototype	void LL_USART_EnableIT_RXNE(USART_TypeDef *USARTx)
function description	Enable specified USART peripheral receive interrupt
Input parameters	USARTx：USARTx handle address
return value	none

function：LL_USART_IsEnabledIT_RXNE

function prototype	uint32_t LL_USART_IsEnabledIT_RXNE(const USART_TypeDef *USARTx)
function description	Check whether the receive data register non-empty interrupt of the specified USART peripheral is enabled
Input parameters	USARTx：USARTx handle address
return value	0 (disabled), 1 (enabled)

5. Experimental phenomena

After successfully downloading the program, press the RESET button on the development board to open the serial port debugging assistant to observe the phenomenon!


xxxxxxxxxx
For program download, please refer to [2. Development environment construction and use: program download and simulation]

Phenomenon:

Use the serial port debugging assistant to send information, and you can see that the serial port returns the same information.

Button control (EXTI)

Voltage detection (ADC)