The code of this article refers to the punctual atomic routine
Article directory
Experimental features
In the punctual atomic routine, the global array is USART_RX_BUF[USART_REC_LEN]used to store the data received by the serial port, and two bits are used as flag bits (reception completion flag).
u8 USART_RX_BUF[USART_REC_LEN]; //接收缓冲,最大USART_REC_LEN个字节.
//接收状态
//bit15， 接收完成标志
//bit14， 接收到0x0d
//bit13~0， 接收到的有效字节数目
u16 USART_RX_STA = 0; //接收状态标记
Routine source code: (main.c)
This experiment realizes the receiving and sending of the serial port. Whether the receiving is completed is judged in the serial port interrupt service function (see the USART1_IRQHandler()function ).
#include "sys.h"
#include "usart.h"
#include "delay.h"
#include "led.h"
#include "beep.h"
#include "key.h"
/*********************************************************************************
___ _ _____ _____ _ _ _____ _____ _ __
/ _ \ | | |_ _|| ___|| \ | ||_ _|| ___|| | / /
/ /_\ \| | | | | |__ | \| | | | | |__ | |/ /
| _ || | | | | __| | . ` | | | | __| | \
| | | || |_____| |_ | |___ | |\ | | | | |___ | |\ \
\_| |_/\_____/\___/ \____/ \_| \_/ \_/ \____/ \_| \_/
* ******************************************************************************
* 正点原子 Pandora STM32L475 IoT开发板 实验4
* 串口通讯实验 HAL库版本
* 技术支持：www.openedv.com
* 淘宝店铺：http://openedv.taobao.com
* 关注微信公众平台微信号："正点原子"，免费获取STM32资料。
* 广州市星翼电子科技有限公司
* 作者：正点原子 @ALIENTEK
* ******************************************************************************/
int main(void)
{
u8 len;
u16 times = 0;
HAL_Init();
SystemClock_Config(); //初始化系统时钟为80M
delay_init(80); //初始化延时函数 80M系统时钟
uart_init(115200); //初始化串口，波特率为115200
LED_Init(); //初始化LED
KEY_Init(); //初始化KEY
while(1)
{
if(USART_RX_STA & 0x8000)
{
len = USART_RX_STA & 0x3fff; //得到此次接收到的数据长度
printf("\r\n您发送的消息为:\r\n");
HAL_UART_Transmit(&UART1_Handler, (uint8_t*)USART_RX_BUF, len, 1000); //发送接收到的数据
while(__HAL_UART_GET_FLAG(&UART1_Handler, UART_FLAG_TC) != SET); //等待发送结束
printf("\r\n\r\n");//插入换行
USART_RX_STA = 0;
}
else
{
times++;
if(times % 5000 == 0)
{
printf("\r\nALIENTEK 潘多拉 STM32L475 IOT开发板 串口实验\r\n");
printf("正点原子@ALIENTEK\r\n\r\n\r\n");
}
if(times % 200 == 0)printf("请输入数据,以回车键结束\r\n");
if(times % 30 == 0)LED_B_TogglePin; //闪烁LED,提示系统正在运行.
delay_ms(10);
}
}
}
Code Analysis
HAL_Init()
HAL_Init()The definition is as follows: (see the notes for the specific functions implemented)
HAL_StatusTypeDef HAL_Init(void)
{
HAL_StatusTypeDef status = HAL_OK;
/* 配置 Flash 预取，指令缓存，数据缓存 */
/* 默认配置为：预存取关闭 指令缓存和数据缓存开启 */
#if (INSTRUCTION_CACHE_ENABLE == 0) // Flash开启预存取配置，能加速CPU代码的执行
__HAL_FLASH_INSTRUCTION_CACHE_DISABLE();
#endif /* INSTRUCTION_CACHE_ENABLE */
#if (DATA_CACHE_ENABLE == 0)
__HAL_FLASH_DATA_CACHE_DISABLE();
#endif /* DATA_CACHE_ENABLE */
#if (PREFETCH_ENABLE != 0)
__HAL_FLASH_PREFETCH_BUFFER_ENABLE();
#endif /* PREFETCH_ENABLE */
/* Set Interrupt Group Priority */
HAL_NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_2); // 配置 NVIC 优先级分组
/* Use SysTick as time base source and configure 1ms tick (default clock after Reset is MSI) */
if (HAL_InitTick(TICK_INT_PRIORITY) != HAL_OK) //初始化滴答定时器，时钟节拍设置为 1ms
{
status = HAL_ERROR;
}
else
{
/* Init the low level hardware */
HAL_MspInit(); // 低速的外设初始化，比如 GPIO、中断等的设置（使用 STM32CubeMx 生成代码时会将低速外设初始
// 代码当这类函数里，其他情况下可以忽略这个函数
}
/* Return function status */
return status;
}
HAL_InitTick()
tick timer clock tick initialization function
__weak HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
{
HAL_StatusTypeDef status = HAL_OK;
/*Configure the SysTick to have interrupt in 1ms time basis*/
if (HAL_SYSTICK_Config(SystemCoreClock/1000UL) != 0U) // 系统时钟/1000，中断周期为 1ms
{
status = HAL_ERROR;
}
else
{
/*Configure the SysTick IRQ priority */
HAL_NVIC_SetPriority(SysTick_IRQn, TickPriority, 0); // 将滴答定时器的中断优先级设置为最高
}
/* Return function status */
return status;
}
SystemClock_Config()
SystemClock_Config()The function definition is as follows: (For the specific implementation of the function, see the comments, for reference only)
void SystemClock_Config(void)
{
HAL_StatusTypeDef ret = HAL_OK;
RCC_OscInitTypeDef RCC_OscInitStruct; // 定义振荡器初始化结构体变量
RCC_ClkInitTypeDef RCC_ClkInitStruct; // 定义时钟初始化结构体变量
__HAL_RCC_PWR_CLK_ENABLE(); // 使能电源控制时钟
/*Initializes the CPU, AHB and APB busses clocks*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE; // 将 HSE（外部高速时钟）作为时钟源
RCC_OscInitStruct.HSEState = RCC_HSE_ON; // 开启 HSE
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON; // 开启 PLL（锁相环）
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE; // 将 HSE 作为 PLL 的时钟源
RCC_OscInitStruct.PLL.PLLM = 1; // PLL-VCO 输入时钟分频系数，1 表示 2 分频（8 / 2 = 4M，本开发板外部晶振频率为 8MHz）
RCC_OscInitStruct.PLL.PLLN = 20; // PLL-VCO 输出时钟倍频系数，4 * 20 = 80M，即输出时钟频率为 80MHz
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7; // SAI 时钟的分频系数
RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2; // SDMMC1, RNG 和 USB 的时钟分频系数
RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2; // 主系统时钟的分频系数
ret = HAL_RCC_OscConfig(&RCC_OscInitStruct); //初始化时钟配置
if(ret != HAL_OK) while(1);
/*Initializes the CPU, AHB and APB busses clocks*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2; // 将所有时钟同时进行配置
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK; // 将 PLL 作为系统时钟源
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1; // AHB 不分频
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1; // APB1 不分频
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1; // APB2 不分频
ret = HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4); // 配置时钟初始结构体变量，
//使用 Flash 延迟4，等待状态(延迟)的数量需要根据CPU时钟(HCLK)的频率和内部电压范围来选择，具体怎么
//选需要参考芯片手册
if(ret != HAL_OK) while(1);
/*Configure the main internal regulator output voltage*/
ret = HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1); //内部寄存器输出电压配置
// 下面是 HAL_PWREx_ControlVoltageScaling() 函数说明的部分内容：
//PWR_REGULATOR_VOLTAGE_SCALE1 Regulator voltage output range 1 mode, typical output voltage
// at 1.2 V, system frequency up to 80 MHz.
if(ret != HAL_OK) while(1);
}
delay_init()
The tick timer has HAL_Init()been initialized in , and the following function actually fac_usassigns a value (currently not involving the operating system, and other codes will not be studied for the time being).
static u32 fac_us = 0; //us延时倍乘数
/**
* @brief 初始化延迟函数,SYSTICK的时钟固定为AHB时钟
*
* @param SYSCLK 系统时钟频率
*
* @return void
*/
void delay_init(u8 SYSCLK)
{
#if SYSTEM_SUPPORT_OS //如果需要支持OS.
u32 reload;
#endif
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);//SysTick频率为HCLK
fac_us = SYSCLK; //不论是否使用OS,fac_us都需要使用
#if SYSTEM_SUPPORT_OS //如果需要支持OS.
reload = SYSCLK; //每秒钟的计数次数 单位为K
reload *= 1000000 / delay_ostickspersec; //根据delay_ostickspersec设定溢出时间
//reload为24位寄存器,最大值:16777216,在80M下，约209.7ms左右
fac_ms = 1000 / delay_ostickspersec; //代表OS可以延时的最少单位
SysTick->CTRL |= SysTick_CTRL_TICKINT_Msk; //开启SYSTICK中断
SysTick->LOAD = reload; //每1/OS_TICKS_PER_SEC秒中断一次
SysTick->CTRL |= SysTick_CTRL_ENABLE_Msk; //开启SYSTICK
#else
#endif
}
usart_Init()
The initialization function of the serial port, the related GPIO initialization is not in this function (but in fact, the GPIO configuration is also performed in this function).
/**
* @brief 初始化串口1函数
*
* @param bound 串口波特率
*
* @return void
*/
void uart_init(u32 bound)
{
//UART 初始化设置
UART1_Handler.Instance = USART1; //USART1
UART1_Handler.Init.BaudRate = bound; //波特率
UART1_Handler.Init.WordLength = UART_WORDLENGTH_8B; //字长为8位数据格式
UART1_Handler.Init.StopBits = UART_STOPBITS_1; //一个停止位
UART1_Handler.Init.Parity = UART_PARITY_NONE; //无奇偶校验位
UART1_Handler.Init.HwFlowCtl = UART_HWCONTROL_NONE; //无硬件流控
UART1_Handler.Init.Mode = UART_MODE_TX_RX; //收发模式
HAL_UART_Init(&UART1_Handler); //HAL_UART_Init()会使能UART1
__HAL_UART_ENABLE_IT(&UART1_Handler, UART_IT_RXNE); //开启接收中断
HAL_NVIC_EnableIRQ(USART1_IRQn); //使能USART1中断通道
HAL_NVIC_SetPriority(USART1_IRQn, 3, 3); //抢占优先级3，子优先级3
}
In the above HAL_UART_Init()function , HAL_UART_MspInit()HAL_UART_MspInit() will call this function to configure the pins and interrupt functions of the serial port. The definition of this function in the routine is as follows:
/**
* @brief HAL库串口底层初始化，时钟使能，引脚配置，中断配置
*
* @param huart 串口句柄
*
* @return void
*/
void HAL_UART_MspInit(UART_HandleTypeDef *huart)
{
//GPIO端口设置
GPIO_InitTypeDef GPIO_Initure;
if(huart->Instance == USART1) //如果是串口1，进行串口1 MSP初始化
{
__HAL_RCC_GPIOA_CLK_ENABLE(); //使能GPIOA时钟
__HAL_RCC_USART1_CLK_ENABLE(); //使能USART1时钟
GPIO_Initure.Pin = GPIO_PIN_9; //PA9
GPIO_Initure.Mode = GPIO_MODE_AF_PP; //复用推挽输出
GPIO_Initure.Pull = GPIO_PULLUP; //上拉
GPIO_Initure.Speed = GPIO_SPEED_FAST; //高速
GPIO_Initure.Alternate = GPIO_AF7_USART1; //复用为USART1
HAL_GPIO_Init(GPIOA, &GPIO_Initure); //初始化PA9
GPIO_Initure.Pin = GPIO_PIN_10; //PA10
HAL_GPIO_Init(GPIOA, &GPIO_Initure); //初始化PA10
}
}
LED_Init()
The GPIOs corresponding to the pins of the LEDs are configured in the LED initialization function.
/**
* @brief LED IO初始化函数
*
* @param void
*
* @return void
*/
void LED_Init(void)
{
/*
LED-B PE9
LED-G PE8
LED-R PE7
*/
GPIO_InitTypeDef GPIO_InitStruct; // 定义一个GPIO初始化结构体变量
__HAL_RCC_GPIOE_CLK_ENABLE(); // 使能GPIOE的时钟
GPIO_InitStruct.Pin = GPIO_PIN_7 | GPIO_PIN_8 | GPIO_PIN_9; // 同时配置 3 个引脚
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP; // 推挽输出模式
GPIO_InitStruct.Pull = GPIO_PULLUP; // 默认上拉
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH; // 速度设为高速（25 MHz to 50 MHz）
HAL_GPIO_Init(GPIOE, &GPIO_InitStruct); // 初始化结构体变量
// 将 3 个引脚同时置高
HAL_GPIO_WritePin(GPIOE, GPIO_PIN_7 | GPIO_PIN_8 | GPIO_PIN_9, GPIO_PIN_SET);
}
delay_ms()
delay_ms()What is running here is delay_us()that the delay is delay_us()realized through a tick timer. The above delay_init()has set fac_us to 80, and it takes 10-6 seconds for the tick timer to count 80 times (the system clock is 80MHz), which is 1us.
/**
* @brief 延时毫秒(ms)函数
*
* @param nms 需要延时多少毫秒
*
* @return void
*/
void delay_ms(u16 nms)
{
u32 i;
for(i = 0; i < nms; i++) delay_us(1000);
}
/**
* @brief 延时微秒(us)函数
*
* @remark nus:0~190887435(最大值即2^32/fac_us@fac_us=22.5)
*
* @param nus 需要延时多少微秒
*
* @return void
*/
void delay_us(u32 nus)
{
u32 ticks;
u32 told, tnow, tcnt = 0;
u32 reload = SysTick->LOAD; //LOAD的值
ticks = nus * fac_us; //需要的节拍数
told = SysTick->VAL; //刚进入时的计数器值
while(1)
{
tnow = SysTick->VAL;
if(tnow != told)
{
if(tnow < told)tcnt += told - tnow; //这里注意一下SYSTICK是一个递减的计数器就可以了.
else tcnt += reload - tnow + told;
told = tnow;
if(tcnt >= ticks)break; //时间超过/等于要延迟的时间,则退出.
}
}
}
HAL_UART_Transmit()
Serial port sending function, the function prototype is as follows:
/**
* @brief Send an amount of data in blocking mode.
* @note When FIFO mode is enabled, writing a data in the TDR register adds one
* data to the TXFIFO. Write operations to the TDR register are performed
* when TXFNF flag is set. From hardware perspective, TXFNF flag and
* TXE are mapped on the same bit-field.
* @param huart UART handle. 串口句柄
* @param pData Pointer to data buffer. 要发送的数据
* @param Size Amount of data to be sent. 要发送的数据大小
* @param Timeout Timeout duration. 超时时间
* @retval HAL status
*/
HAL_StatusTypeDef HAL_UART_Transmit(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout)
Serial port read and write status
main() function
while(__HAL_UART_GET_FLAG(&UART1_Handler, UART_FLAG_TC) != SET); //等待发送结束
It is used to obtain the completion status of the serial port transmission. Similar status bits are:
#define UART_FLAG_TXE USART_ISR_TXE /*!< 串口发送数据空 */
#define UART_FLAG_TC USART_ISR_TC /*!< 串口发送数据完成 */
#define UART_FLAG_RXNE USART_ISR_RXNE_RXFNE /*!< 串口读取数据寄存器非空 */
#define UART_FLAG_RXFNE USART_ISR_RXNE_RXFNE /*!< 串口接收缓存非空 */
#define UART_FLAG_RXNE USART_ISR_RXNE /*!< 串口读数据非空 */
#define UART_FLAG_IDLE USART_ISR_IDLE /*!< 串口空闲标志 */
#define UART_FLAG_ORE USART_ISR_ORE /*!< UART overrun error */
#define UART_FLAG_NE USART_ISR_NE /*!< UART noise error */
#define UART_FLAG_FE USART_ISR_FE /*!< UART frame error */
#define UART_FLAG_PE USART_ISR_PE /*!< UART parity error */
redirect printf()
Add the following code to the project, you can use to printf()print data to the serial port.
#if 1
#pragma import(__use_no_semihosting)
//标准库需要的支持函数
struct __FILE
{
int handle;
};
FILE __stdout;
/**
* @brief 定义_sys_exit()以避免使用半主机模式
*
* @param void
*
* @return void
*/
void _sys_exit(int x)
{
x = x;
}
/**
* @brief 重定义fputc函数
*
* @param ch 输出字符量
* @param f 文件指针
*
* @return void
*/
int fputc(int ch, FILE *f)
{
while((USART1->ISR & 0X40) == 0); //循环发送,直到发送完毕
USART1->TDR = (u8) ch;
return ch;
}
#endif
LED operation function
The control function of LED is a macro function, which uses HAL_GPIO_WritePin()and HAL_GPIO_TogglePin()two library functions respectively.
#define LED_B(n) (n?HAL_GPIO_WritePin(GPIOE,GPIO_PIN_9,GPIO_PIN_SET):HAL_GPIO_WritePin(GPIOE,GPIO_PIN_9,GPIO_PIN_RESET))
#define LED_B_TogglePin HAL_GPIO_TogglePin(GPIOE,GPIO_PIN_9)
USART1_IRQHandler()
The comment of the routine declares that this experiment does not use the processing logic of the HAL library (using the callback function), but uses the method of directly defining the interrupt service function. The code logic is not complicated, and detailed comments have been given in the routine.
u8 USART_RX_BUF[USART_REC_LEN]; //接收缓冲,最大USART_REC_LEN个字节.
//接收状态
//bit15， 接收完成标志
//bit14， 接收到0x0d
//bit13~0， 接收到的有效字节数目
u16 USART_RX_STA = 0; //接收状态标记
/**
* @brief 串口1中断服务程序
*
* @remark 下面代码我们直接把中断控制逻辑写在中断服务函数内部
* 说明：采用HAL库处理逻辑，效率不高。
*
* @param void
*
* @return void
*/
void USART1_IRQHandler(void)
{
u8 Res;
if((__HAL_UART_GET_FLAG(&UART1_Handler, UART_FLAG_RXNE) != RESET)) //接收中断(接收到的数据必须是0x0d 0x0a结尾)
{
HAL_UART_Receive(&UART1_Handler, &Res, 1, 1000);
if((USART_RX_STA & 0x8000) == 0) //接收未完成
{
if(USART_RX_STA & 0x4000) //接收到了0x0d
{
if(Res != 0x0a)USART_RX_STA = 0; //接收错误,重新开始
else USART_RX_STA |= 0x8000; //接收完成了
}
else //还没收到0X0D
{
if(Res == 0x0d)USART_RX_STA |= 0x4000;
else
{
USART_RX_BUF[USART_RX_STA & 0X3FFF] = Res ;
USART_RX_STA++;
if(USART_RX_STA > (USART_REC_LEN - 1))USART_RX_STA = 0; //接收数据错误,重新开始接收
}
}
}
}
HAL_UART_IRQHandler(&UART1_Handler);
}
HAL_UART_Receive()
Serial port receiving function, the function prototype is as follows:
/**
* @brief Receive an amount of data in blocking mode.
* @note When FIFO mode is enabled, the RXFNE flag is set as long as the RXFIFO
* is not empty. Read operations from the RDR register are performed when
* RXFNE flag is set. From hardware perspective, RXFNE flag and
* RXNE are mapped on the same bit-field.
* @param huart UART handle. 串口句柄
* @param pData Pointer to data buffer. 接收的数据缓存
* @param Size Amount of data to be received. 要接收的数据大小
* @param Timeout Timeout duration. 超时时间
* @retval HAL status
*/
HAL_StatusTypeDef HAL_UART_Receive(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout)
HAL_UART_IRQHandler()
The function is called on USART1_IRQHandler()the last line of , and here HAL_UART_IRQHandler()'s how others on the Internet explain this function:
Call the HAL library interrupt handling public functions. Function: Judging and processing the received data, judging whether it is a sending interrupt or a receiving interrupt, and then sending and receiving data, which is used in the interrupt service function.
——https://www.csdn.net/tags/MtjaYgxsMzE5MTYtYmxvZwO0O0OO0O0O.html
