Serial communication test bull knife

Posted by lkq on Sat, 30 Oct 2021 14:54:11 +0200

1, USART serial communication program of STM32

1.USART introduction

1. Baidu Encyclopedia:

  • Universal synchronous / asynchronous serial receiver / transmitter
  • USART is a full duplex universal synchronous / asynchronous serial transceiver module. The interface is a highly flexible serial communication device.

2. Main features

  • Full duplex operation (receiving data and transmitting data independently of each other);

  • During synchronous operation, the master clock can be synchronized, and the slave clock can also be synchronized;

  • Independent high-precision baud rate generator, does not occupy timing / counter;

  • Serial data frame structure supporting 5, 6, 7, 8 and 9 data bits and 1 or 2 stop bits;

  • Parity bit generation and verification supported by hardware;

  • Data overflow detection;

  • Frame error detection;

  • A detection noise filter including an error start bit and a digital low-pass filter;

  • Three completely independent interrupts, TX transmission completed, TX transmission data register empty, RX reception completed;

  • Support multi computer communication mode;

  • Support double speed asynchronous communication mode.

2.USART configuration:

  • STM32 still needs to configure priority when there is only one interrupt. Its function is to enable the trigger channel of an interrupt. The interrupt of STM32 has at most two levels: preemptive priority (Master priority) and sub priority (slave priority). The length of the whole priority setting parameter is 4 bits. Therefore, it is necessary to first divide the preemptive priority bits and sub priority bits through NVIC_PriorityGroupConfig() implementation;
  • The attributes of the interrupt priority NVIC of a specific device are contained in the structure NVIC_InitTypeDef, where field NVIC_IRQChannel contains the interrupt vector of the device and is saved in the startup code; Field NVIC_IRQChannelPreemptionPriority, NVIC_IRQChannelSubPriority is slave priority, and the range of values shall be determined according to the division of digits; Finally, NVIC_ The irqchannelcmd field is enabled, which is generally set to ENABLE. Finally, through NVIC_Init() enables this interrupt vector.

3. Compilation implementation

1. Open keil project new peoject

2. Create a new file

3. Chip selection STM32F103C8

4. Create a new main.s

5. Code:

;RCC Register address mapping             
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 Register address mapping            
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 Register address mapping              
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 Mouth control                   
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) 
;Serial port 1 control                       
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 Register address                
NVIC_BASE           EQU    0xE000E000 
NVIC_SETEN          EQU    (NVIC_BASE + 0x0010)     
;SETENA Starting address of register array 
NVIC_IRQPRI         EQU    (NVIC_BASE + 0x0400)     
;Start address of interrupt priority register array 
NVIC_VECTTBL        EQU    (NVIC_BASE + 0x0D08)     
;Address of vector table offset register     
NVIC_AIRCR          EQU    (NVIC_BASE + 0x0D0C)     
;Address of application interrupt and reset control register                                                
SETENA0             EQU    0xE000E100 
SETENA1             EQU    0xE000E104 
;SysTick Register address            
SysTick_BASE        EQU    0xE000E010 
SYSTICKCSR          EQU    (SysTick_BASE + 0x00) 
SYSTICKRVR          EQU    (SysTick_BASE + 0x04) 
;FLASH Buffer register address image     
FLASH_ACR           EQU    0x40022000 
;SCB_BASE           EQU    (SCS_BASE + 0x0D00) 
MSP_TOP             EQU    0x20005000               
;Starting value of main stack                
PSP_TOP             EQU    0x20004E00               
;Process stack start value             
BitAlias_BASE       EQU    0x22000000               
;Bit alias area start address         
Flag1               EQU    0x20000200 
b_flas              EQU    (BitAlias_BASE + (0x200*32) + (0*4))               
;Bit address 
b_05s               EQU    (BitAlias_BASE + (0x200*32) + (1*4))               
;Bit address 
DlyI                EQU    0x20000204 
DlyJ                EQU    0x20000208 
DlyK                EQU    0x2000020C 
SysTim              EQU    0x20000210 

;Constant definition 
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 

;Vector table 
    DCD    MSP_TOP            ;Initialize main stack 
    DCD    Start              ;Reset vector 
    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                 ;Reserved space 20 bytes                 
;Code snippet 
    AREA |.text|, CODE, READONLY 
    ;Main program start 
    ;Instructs the program to execute from here 
    ;Clock system settings 
    ldr    r0, =RCC_CR 
    ldr    r1, [r0] 
    orr    r1, #Bit16 
    str    r1, [r0] 
    ;Enable external crystal oscillator  
    ;Start external 8 M Crystal oscillator 
    ldr    r1, [r0] 
    ands   r1, #Bit17 
    beq    ClkOk 
    ;Wait for the external crystal oscillator to be ready 
    ldr    r1,[r0] 
    orr    r1,#Bit17 
    str    r1,[r0] 
    ;FLASH Buffer 
    ldr    r0, =FLASH_ACR 
    mov    r1, #0x00000032 
    str    r1, [r0] 
    ;set up PLL The PLL magnification is 7,HSE Input no frequency division 
    ldr    r0, =RCC_CFGR 
    ldr    r1, [r0] 
    orr    r1, #(Bit18 :OR: Bit19 :OR: Bit20 :OR: Bit16 :OR: Bit14) 
    orr    r1, #Bit10 
    str    r1, [r0] 
    ;start-up PLL Phase locked loop 
    ldr    r0, =RCC_CR 
    ldr    r1, [r0] 
    orr    r1, #Bit24 
    str    r1, [r0] 
    ldr    r1, [r0] 
    ands   r1, #Bit25 
    beq    PllOk 
    ;choice PLL Clock as system clock 
    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] 
    ;other RCC Related settings 
    ldr    r0, =RCC_APB2ENR 
    mov    r1, #(Bit14 :OR: Bit4 :OR: Bit2) 
    str    r1, [r0]      
    ;PA9 Serial port 0 transmitting pin 
    ldr    r0, =GPIOA_CRH 
    ldr    r1, [r0] 
    orr    r1, #(Bit4 :OR: Bit5)          
    ;PA.9 Output mode,Maximum speed 50 MHz  
    orr    r1, #Bit7 
    and    r1, #~Bit6 
    ;10: Multiplexing function push-pull output mode 
    str    r1, [r0]    

    ldr    r0, =USART1_BRR   
    mov    r1, #0x271 
    str    r1, [r0] 
    ;Configure baud rate-> 115200 
    ldr    r0, =USART1_CR1   
    mov    r1, #0x200c 
    str    r1, [r0] 
    ;USART Module total enable send and receive enable 
    ;71 02 00 00   2c 20 00 00 
    ;AFIO Parameter setting             
    ;Systick Parameter setting 
    ldr    r0, =SYSTICKRVR           
    ;Systick Initial installation value 
    mov    r1, #9000 
    str    r1, [r0] 
    ldr    r0, =SYSTICKCSR           
    ;set up,start-up Systick 
    mov    r1, #0x03 
    str    r1, [r0] 
    ;Switch to user level line program mode 
    ldr    r0, =PSP_TOP                   
    ;Initialize thread stack 
    msr    psp, r0 
    mov    r0, #3 
    msr    control, r0 
    ;initialization SRAM register 
    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 cycle            
    ldr    r0, =Flag1 
    ldr    r1, [r0] 
    tst    r1, #Bit1                 
    ;SysTick Generate 0.5s,Set bit 1 
    beq    main                  ;0.5s The flag is not set yet       
    ;0.5s The flag has been set 
    ldr    r0, =b_05s                
    ;Bit band operation reset 0.5s sign 
    mov    r1, #0 
    str    r1, [r0] 

    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, #'i' 
    bl     send_a_char
	mov    r0, #'n' 
    bl     send_a_char
	mov    r0, #'d' 
    bl     send_a_char
	mov    r0, #'o' 
    bl     send_a_char
	mov    r0, #'w' 
    bl     send_a_char
	mov    r0, #'\n' 
    bl     send_a_char
	b      main
;Subroutine serial port 1 sends a character 
    push   {r0 - r3} 
    ldr    r2, =USART1_DR   
    str    r0, [r2] 
    ldr    r2, =USART1_SR  
    ldr    r2, [r2] 
    tst    r2, #0x40 
    beq    b1 
    ;Send complete(Transmission complete)wait for 
    pop    {r0 - r3} 
    bx     lr 
;Abnormal program 
    bx     lr 

    bx     lr 
    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  
    ;The clock tick counter is set to 0 when it is greater than or equal to 500 times of clearing.5s Flag bit 
    ;Bit band operation set 1 
    mov    r1, #1 
    str    r1, [r0] 
    bx     lr 
    ;By using zero or null instructions NOP fill,Aligns the current position with a specified boundary 


8. Waveform diagram

2, Summary

This assignment is to learn about the serial port protocol and RS-232 standard, the difference between RS232 level and TTL level, and the working principle of USB/TTL to 232. More understanding and familiarity with embedded operation, but also exposed more problems, which need to be improved. I hope it can be solved in future learning, so that the homework can be completed more smoothly.

3, References

Topics: Single-Chip Microcomputer stm32