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 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
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