Serial communication test bull knife

catalogue

1, Understand the serial port protocol and RS-232 standard, as well as the difference between RS232 level and TTL level; Understand the working principle of "USB/TTL to 232" module (taking CH340 chip module as an example).

2, Installing stm32CubeMX

3, Cooperate with Keil and use register mode (assembly or C, unlimited) or HAL library to complete the following tasks:

1. Redo the last led flow light operation, that is, complete the periodic flashing of three LED traffic lights with GPIO port.

2. Complete a USART serial communication program of STM32 (query mode is OK, interrupt mode is not required temporarily)

4, Observe the waveform through keil

5, Summary

6, Reference link

1, Understand the serial port protocol and RS-232 standard, as well as the difference between RS232 level and TTL level; Understand the working principle of "USB/TTL to 232" module (taking CH340 chip module as an example).

Serial communication and RS-232 protocol: send and receive bytes by bit. Although it is slower than byte serial communication, the serial port can use one line to send data and another line to receive data. Serial communication protocol refers to the relevant specifications that specify the content of data packet, including start bit, main data, check bit and stop bit. Both parties need to agree on a consistent data packet format to send and receive data normally. In serial communication, common protocols include RS-232, RS-422 and RS-485. RS-232 (ANSI/EIA-232 standard) is a serial connection standard on IBM-PC and its compatible computers. It can be used for many purposes, such as connecting mouse, printer or Modem, and industrial instruments. For the improvement of drive and connection, the transmission length or speed of RS-232 often exceeds the standard value in practical application. RS-232 is only limited to point-to-point communication between PC serial port devices. The maximum distance of RS-23 serial communication is 50 feet.

Difference between RS232 level and TTL level: TTL level signal is widely used because we usually use binary to represent data. Moreover, it is specified that + 5V is equivalent to logic "1" and 0V is equivalent to logic "0". Such data communication and level specification mode is called TTL (transistor transistor logic level) signal system. This is the standard technology of communication between various parts of equipment controlled by computer processor. RS232 is one of the communication interfaces on personal computer. It is an asynchronous transmission standard interface formulated by Electronic Industries AssociaTIon (EIA). Generally, RS-232 interfaces appear in the form of 9 pins (DB-9) or 25 pins (DB-25). Generally, there are two groups of RS-232 interfaces on personal computers, called COM1 and COM2 respectively. The level standard of RS232 is + 12V for logic negative, - 12 for logic positive, TTL level is 5V for logic positive, and 0 for logic negative.

Working principle of "USB/TTL to 232" module (taking CH340 chip module as an example): USB to TTL serial port module is a very practical tool, which can test the UART serial port communication of the module and download programs to the MCU through the UART interface of the MCU. The serial port assistant software on the computer can intuitively display the data returned by the serial port device and send the corresponding control data to the serial port device. The common USB to serial port modules are CP2102, PL2303, FT232, CH340 and other serial port chip schemes. The following takes CH340 serial port module as an example for self-test.

schematic diagram:

2, Installing stm32CubeMX

1. Install jdk
Since STM32CubeMX is implemented in Java, the jdk environment needs to be installed.
jdk official website download link:
Java Downloads | Oracle

 

  2. Install STM32CubeMX
Download address:
STM32CubeMX - STM32Cube initialization code generator - STMicroelectronics

Do not include English in the installation path:

 

3. Install the firmware library

  Open cubeMX and select manage under help

  Click Install Now

  A green dot indicates successful installation

3, Cooperate with Keil and use register mode (assembly or C, unlimited) or HAL library to complete the following tasks:

1. Redo the last led flow light operation, that is, complete the periodic flashing of three LED traffic lights with GPIO port.

schematic diagram:

Create a new project

  Double click to enter stm32f103c8  

Click System Core, enter SYS, and select Serial Wire in debug

  Set system clock mux from HSI to PLLOCK

  Set the clock RCC and select Crystal/Ceramic Resonator in High Speed Clock

Select pins PA12,PB1, and PC14 and click GPIO_Output

  Select GPIO output level high

  Select project manager to create a project, enter the project name and address, and select MDK-ARM in Toolchain/IDE

  Enter the code generate interface, select generate initialization. c/.h file, and then click generate code

  Open folder directly

Open the generated project file

  Add the light on and light off code in the while cycle:

        HAL_GPIO_WritePin(GPIOA,GPIO_PIN_12,GPIO_PIN_SET);//PA12 lights out
		HAL_Delay(500);//Delay 0.5s
		HAL_GPIO_WritePin(GPIOA,GPIO_PIN_12,GPIO_PIN_RESET);//PA12 on
		HAL_Delay(500);//Delay 0.5s		
		HAL_GPIO_WritePin(GPIOB,GPIO_PIN_1,GPIO_PIN_SET);//PB1 off
		HAL_Delay(500);//Delay 0.5s
		HAL_GPIO_WritePin(GPIOB,GPIO_PIN_1,GPIO_PIN_RESET);//PB1 on
		HAL_Delay(500);//Delay 0.5s
		
		HAL_GPIO_WritePin(GPIOC,GPIO_PIN_14,GPIO_PIN_SET);//PC14 lights out
		HAL_Delay(500);//Delay 0.5s
		
		HAL_GPIO_WritePin(GPIOC,GPIO_PIN_14,GPIO_PIN_RESET);//PC14 on
		HAL_Delay(500);//Delay 0.5s

  Compile without error to generate HEX file

  Connect the core board and open mcuisp for burning

  Result display:

2. Complete a USART serial communication program of STM32 (query mode is OK, interrupt mode is not required temporarily)

requirement:

1) Set the baud rate to 115200, 1 stop bit and no check bit;

2) STM32 system continuously sends "hello windows!" to the upper computer (win10). Win10 uses the "serial port assistant" tool to receive.

Create a new project

Add tiaoshi.s file

Add assembly 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 
    AREA RESET, DATA, READONLY 
    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 
    ENTRY                            
    ;Instructs the program to execute from here 
Start 
    ;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 
                                            
ClkOk           
    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] 
PllOk 
    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            
main            
    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, #'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
            
              
            
;Subroutine serial port 1 sends a character 
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 
    ;Send complete(Transmission complete)wait for 
    pop    {r0 - r3} 
    bx     lr 
                                
;Abnormal program 
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  
    ;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] 
TickExit    
    bx     lr 
                                                                           
    ALIGN            
    ;By using zero or null instructions NOP fill,Aligns the current position with a specified boundary 
    END

Debug compile generate hex file

  Set boot to 1 and burn the hex file into the core board

Open the serial port debugging assistant and connect the port. The baud rate is 115200 by default, 1 stop bit and no check bit.

Open the hex file just generated, click send file, then set boot0 to 0, and click reset to receive hello world:

4, Observe the waveform through keil

Title:

Without an oscilloscope, Keil's software simulation logic analyzer function can be used to observe the timing waveform of the pin, which is more convenient for dynamic tracking, debugging and locating the code fault point. Please use this function to observe the output waveform of the three GPIO ports in question 1 and the serial port output waveform in question 2, and analyze whether the timing state reflected by the waveform is correct and the actual high-low level conversion cycle (LED flashing cycle).

Environment settings

Modify Debug parameters:

Output waveform observation of three GPIO ports in question 1:

Enter the debugging mode, open the logic analysis function, select setup and create the pin.

 

Click Run to run the program, and it can be seen that the three pins appear alternately in the cycle of 0.5s, so as to realize the flashing of water flow lamp:

Observation of serial port output waveform in question 2:

Set pin to USART1_SR

 

The cycle of hello world program is 0.5s, and the level will change every 0.5s, resulting in periodic output.

5, Summary

        The serial port debugging experiment is relatively difficult. For me, the more difficult points are: installation of STM32CubeMX: the download speed of the official website is too slow, the version found on the Internet is too old to run after opening, and there is no solution on the Internet. But then the latest version of the resource was found and successfully opened. After that, the redo water lamp and serial port debugging experiment is relatively simple, and it doesn't take much time to finish. Through the study of this experiment, I have a deeper understanding of the concept of serial port and debugging.

6, Reference link

Build STM32 development environment - STM32CubeMX, Keil5_Harriet's blog - CSDN blog

stm32 realizes LED flashing -- Based on HAL Library_ Harriet's blog - CSDN blog_ stm32 to achieve LED flashing

Creating STM32 assembler based on MDK: serial port output Hello world_ssj925319 blog - CSDN blog

STM32 minimum core board F103 serial communication USART_ vic_ to_ CSDN blog

Tags: Single-Chip Microcomputer stm32

Posted on Wed, 27 Oct 2021 05:58:14 -0400 by manoj_jnics1