目录
一：串口协议
1.串口通信原理
串口在嵌入式系统当中是一类重要的数据通信接口，其本质功能是作为 CPU 和串行设备间的编码转换器。当数据从 CPU 经过串行端口发送出去时，字节数据转换为串行的位；在接收数据时，串行的位被转换为字节数据。应用程序要使用串口进行通信，必须在使用之前向操作系统提出资源申请要求（打开串口），通信完成后必须释放资源（关闭串口）。典型地，串口用于 ASCII 码字符的传输。
波特率：
串口异步通信中没有时钟信号，所以需要约定好波特率，即码元长度。
起始位、停止位
数据包从起始位开始、停止位结束
常用协议
RS-232（ANSI/EIA-232标准）是IBM-PC及其兼容机上的串行连接标准。可用于许多用途，比如连接鼠标、打印机或者Modem。
RS232电平与TTL电平的区别
TTL电平信号之所以被广泛使用，原因是因为：通常我们采用二进制来表示数据。而且规定，+5V等价于逻辑“1”，0V等价于逻辑“0”。这样的数据通信及电平规定方式，被称做TTL（晶体管-晶体管逻辑电平）信号系统。这是计算机处理器控制的设备内部各部分之间通信的标准技术。
rs232是个人计算机上的通讯接口之一，由电子工业协会（Electronic Industries AssociaTIon，EIA） 所制定的异步传输标准接口。通常 RS-232 接口以9个引脚 （DB-9） 或是25个引脚 （DB-25） 的型态出现，一般个人计算机上会有两组 RS-232 接口，分别称为 COM1 和 COM2。RS232的电平标准为+12V为逻辑负，-12为逻辑正，TTL电平为5V为逻辑正，0为逻辑负
二、利用 stm32CubeMX完成任务
1.流水灯
（1)下载stm32CubeMX
官网：
STM32CubeMX - STM32Cube initialization code generator - STMicroelectronics
由于STM32CubeMX是Java实现的，需要安装jdk环境。
JDK
（2）配置环境（根据截图一步一步操作）
?
?
?
?代码：
#include "main.h"
#include "gpio.h"
int main(void)
{
SystemClock_Config();//???????
MX_GPIO_Init();//gpio???
while (1)
{
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_7,GPIO_PIN_RESET);//PA7??
HAL_Delay(500);//??0.5s
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_7,GPIO_PIN_SET);//PA7??
HAL_Delay(500);//??0.5s
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_9,GPIO_PIN_RESET);//PB9??
HAL_Delay(500);//??0.5s
HAL_GPIO_WritePin(GPIOB,GPIO_PIN_9,GPIO_PIN_SET);//PB9??
HAL_Delay(500);//??0.5s
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_15,GPIO_PIN_RESET);//PC15??
HAL_Delay(500);//??0.5s
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_15,GPIO_PIN_SET);//PC15??
HAL_Delay(500);//??0.5s
}
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI_DIV2;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
?结果：
波形图
2、串口通信
代码：
RCC_BASE EQU 0x40021000
RCC_CR EQU (RCC_BASE + 0x00)
RCC_CFGR EQU (RCC_BASE + 0x04)
RCC_CIR EQU (RCC_BASE + 0x08)
RCC_APB2RSTR EQU (RCC_BASE + 0x0C)
RCC_APB1RSTR EQU (RCC_BASE + 0x10)
RCC_AHBENR EQU (RCC_BASE + 0x14)
RCC_APB2ENR EQU (RCC_BASE + 0x18)
RCC_APB1ENR EQU (RCC_BASE + 0x1C)
RCC_BDCR EQU (RCC_BASE + 0x20)
RCC_CSR EQU (RCC_BASE + 0x24)
;AFIO???????
AFIO_BASE EQU 0x40010000
AFIO_EVCR EQU (AFIO_BASE + 0x00)
AFIO_MAPR EQU (AFIO_BASE + 0x04)
AFIO_EXTICR1 EQU (AFIO_BASE + 0x08)
AFIO_EXTICR2 EQU (AFIO_BASE + 0x0C)
AFIO_EXTICR3 EQU (AFIO_BASE + 0x10)
AFIO_EXTICR4 EQU (AFIO_BASE + 0x14)
;GPIOA???????
GPIOA_BASE EQU 0x40010800
GPIOA_CRL EQU (GPIOA_BASE + 0x00)
GPIOA_CRH EQU (GPIOA_BASE + 0x04)
GPIOA_IDR EQU (GPIOA_BASE + 0x08)
GPIOA_ODR EQU (GPIOA_BASE + 0x0C)
GPIOA_BSRR EQU (GPIOA_BASE + 0x10)
GPIOA_BRR EQU (GPIOA_BASE + 0x14)
GPIOA_LCKR EQU (GPIOA_BASE + 0x18)
;GPIO C???
GPIOC_BASE EQU 0x40011000
GPIOC_CRL EQU (GPIOC_BASE + 0x00)
GPIOC_CRH EQU (GPIOC_BASE + 0x04)
GPIOC_IDR EQU (GPIOC_BASE + 0x08)
GPIOC_ODR EQU (GPIOC_BASE + 0x0C)
GPIOC_BSRR EQU (GPIOC_BASE + 0x10)
GPIOC_BRR EQU (GPIOC_BASE + 0x14)
GPIOC_LCKR EQU (GPIOC_BASE + 0x18)
;??1??
USART1_BASE EQU 0x40013800
USART1_SR EQU (USART1_BASE + 0x00)
USART1_DR EQU (USART1_BASE + 0x04)
USART1_BRR EQU (USART1_BASE + 0x08)
USART1_CR1 EQU (USART1_BASE + 0x0c)
USART1_CR2 EQU (USART1_BASE + 0x10)
USART1_CR3 EQU (USART1_BASE + 0x14)
USART1_GTPR EQU (USART1_BASE + 0x18)
;NVIC?????
NVIC_BASE EQU 0xE000E000
NVIC_SETEN EQU (NVIC_BASE + 0x0010)
;SETENA??????????
NVIC_IRQPRI EQU (NVIC_BASE + 0x0400)
;???????????????
NVIC_VECTTBL EQU (NVIC_BASE + 0x0D08)
;???????????
NVIC_AIRCR EQU (NVIC_BASE + 0x0D0C)
;?????????????????
SETENA0 EQU 0xE000E100
SETENA1 EQU 0xE000E104
;SysTick?????
SysTick_BASE EQU 0xE000E010
SYSTICKCSR EQU (SysTick_BASE + 0x00)
SYSTICKRVR EQU (SysTick_BASE + 0x04)
;FLASH?????????
FLASH_ACR EQU 0x40022000
;SCB_BASE EQU (SCS_BASE + 0x0D00)
MSP_TOP EQU 0x20005000
;??????
PSP_TOP EQU 0x20004E00
;???????
BitAlias_BASE EQU 0x22000000
;?????????
Flag1 EQU 0x20000200
b_flas EQU (BitAlias_BASE + (0x200*32) + (0*4))
;???
b_05s EQU (BitAlias_BASE + (0x200*32) + (1*4))
;???
DlyI EQU 0x20000204
DlyJ EQU 0x20000208
DlyK EQU 0x2000020C
SysTim EQU 0x20000210
;????
Bit0 EQU 0x00000001
Bit1 EQU 0x00000002
Bit2 EQU 0x00000004
Bit3 EQU 0x00000008
Bit4 EQU 0x00000010
Bit5 EQU 0x00000020
Bit6 EQU 0x00000040
Bit7 EQU 0x00000080
Bit8 EQU 0x00000100
Bit9 EQU 0x00000200
Bit10 EQU 0x00000400
Bit11 EQU 0x00000800
Bit12 EQU 0x00001000
Bit13 EQU 0x00002000
Bit14 EQU 0x00004000
Bit15 EQU 0x00008000
Bit16 EQU 0x00010000
Bit17 EQU 0x00020000
Bit18 EQU 0x00040000
Bit19 EQU 0x00080000
Bit20 EQU 0x00100000
Bit21 EQU 0x00200000
Bit22 EQU 0x00400000
Bit23 EQU 0x00800000
Bit24 EQU 0x01000000
Bit25 EQU 0x02000000
Bit26 EQU 0x04000000
Bit27 EQU 0x08000000
Bit28 EQU 0x10000000
Bit29 EQU 0x20000000
Bit30 EQU 0x40000000
Bit31 EQU 0x80000000
;???
AREA RESET, DATA, READONLY
DCD MSP_TOP ;??????
DCD Start ;????
DCD NMI_Handler ;NMI Handler
DCD HardFault_Handler ;Hard Fault Handler
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD 0
DCD SysTick_Handler ;SysTick Handler
SPACE 20 ;????20??
;???
AREA |.text|, CODE, READONLY
;?????
ENTRY
;???????????
Start
;??????
ldr r0, =RCC_CR
ldr r1, [r0]
orr r1, #Bit16
str r1, [r0]
;????????
;????8M??
ClkOk
ldr r1, [r0]
ands r1, #Bit17
beq ClkOk
;????????
ldr r1,[r0]
orr r1,#Bit17
str r1,[r0]
;FLASH???
ldr r0, =FLASH_ACR
mov r1, #0x00000032
str r1, [r0]
;??PLL??????7,HSE?????
ldr r0, =RCC_CFGR
ldr r1, [r0]
orr r1, #(Bit18 :OR: Bit19 :OR: Bit20 :OR: Bit16 :OR: Bit14)
orr r1, #Bit10
str r1, [r0]
;??PLL???
ldr r0, =RCC_CR
ldr r1, [r0]
orr r1, #Bit24
str r1, [r0]
PllOk
ldr r1, [r0]
ands r1, #Bit25
beq PllOk
;??PLL????????
ldr r0, =RCC_CFGR
ldr r1, [r0]
orr r1, #(Bit18 :OR: Bit19 :OR: Bit20 :OR: Bit16 :OR: Bit14)
orr r1, #Bit10
orr r1, #Bit1
str r1, [r0]
;??RCC????
ldr r0, =RCC_APB2ENR
mov r1, #(Bit14 :OR: Bit4 :OR: Bit2)
str r1, [r0]
;IO????
ldr r0, =GPIOC_CRL
ldr r1, [r0]
orr r1, #(Bit28 :OR: Bit29)
;PC.7????,????50MHz
and r1, #(~Bit30 & ~Bit31)
;PC.7????????
str r1, [r0]
;PA9??0???
ldr r0, =GPIOA_CRH
ldr r1, [r0]
orr r1, #(Bit4 :OR: Bit5)
;PA.9????,????50MHz
orr r1, #Bit7
and r1, #~Bit6
;10:??????????
str r1, [r0]
ldr r0, =USART1_BRR
mov r1, #0x271
str r1, [r0]
;?????-> 115200
ldr r0, =USART1_CR1
mov r1, #0x200c
str r1, [r0]
;USART????? ???????
;71 02 00 00 2c 20 00 00
;AFIO ????
;Systick ????
ldr r0, =SYSTICKRVR
;Systick???
mov r1, #9000
str r1, [r0]
ldr r0, =SYSTICKCSR
;??,??Systick
mov r1, #0x03
str r1, [r0]
;NVIC
;ldr r0, =SETENA0
;mov r1, 0x00800000
;str r1, [r0]
;ldr r0, =SETENA1
;mov r1, #0x00000100
;str r1, [r0]
;???????????
ldr r0, =PSP_TOP
;???????
msr psp, r0
mov r0, #3
msr control, r0
;???SRAM???
mov r1, #0
ldr r0, =Flag1
str r1, [r0]
ldr r0, =DlyI
str r1, [r0]
ldr r0, =DlyJ
str r1, [r0]
ldr r0, =DlyK
str r1, [r0]
ldr r0, =SysTim
str r1, [r0]
;???
main
ldr r0, =Flag1
ldr r1, [r0]
tst r1, #Bit1
;SysTick??0.5s,??bit 1
beq main ;0.5s???????
;0.5s??????
ldr r0, =b_05s
;??????0.5s??
mov r1, #0
str r1, [r0]
bl LedFlas
mov r0, #'H'
bl send_a_char
mov r0, #'e'
bl send_a_char
mov r0, #'l'
bl send_a_char
mov r0, #'l'
bl send_a_char
mov r0, #'o'
bl send_a_char
mov r0, #' '
bl send_a_char
mov r0, #'w'
bl send_a_char
mov r0, #'o'
bl send_a_char
mov r0, #'r'
bl send_a_char
mov r0, #'l'
bl send_a_char
mov r0, #'d'
bl send_a_char
mov r0, #'\n'
bl send_a_char
b main
;??? ??1??????
send_a_char
push {r0 - r3}
ldr r2, =USART1_DR
str r0, [r2]
b1
ldr r2, =USART1_SR
ldr r2, [r2]
tst r2, #0x40
beq b1
;????(Transmission complete)??
pop {r0 - r3}
bx lr
;??? led??
LedFlas
push {r0 - r3}
ldr r0, =Flag1
ldr r1, [r0]
tst r1, #Bit0
;bit0 ?????
beq ONLED ;?0 ??led?
;?1 ??led?
ldr r0, =b_flas
mov r1, #0
str r1, [r0]
;???????0,????????
;PC.7??0
ldr r0, =GPIOC_BRR
ldr r1, [r0]
orr r1, #Bit7
str r1, [r0]
b LedEx
ONLED
;?0 ??led?
ldr r0, =b_flas
mov r1, #1
str r1, [r0]
;???????1,????????
;PC.7??1
ldr r0, =GPIOC_BSRR
ldr r1, [r0]
orr r1, #Bit7
str r1, [r0]
LedEx
pop {r0 - r3}
bx lr
;????
NMI_Handler
bx lr
HardFault_Handler
bx lr
SysTick_Handler
ldr r0, =SysTim
ldr r1, [r0]
add r1, #1
str r1, [r0]
cmp r1, #500
bcc TickExit
mov r1, #0
str r1, [r0]
ldr r0, =b_05s
;????500? ????????? ??0.5s???
;?????1
mov r1, #1
str r1, [r0]
TickExit
bx lr
ALIGN
;????????NOP??,????????????????
END
?
?三：总结
这次操作难度不大，交作业难度更大，花在交作业的时间比做作业更多，特别是题目要求交的内容表述不清楚。pdf文件和md文件内容重合，不知所云。