catalogue
4, Observe the waveform through keil
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
ENDDebug 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
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