Debugging in uVision

Overview

In this tutorial, we will learn how to use uVision for debugging firmware programming.

Preparation

• Open your previous tutorial project or can create a new project.

• You can also copy the given example "TU_uVision_Debugging.c" source code here

• You will learn how to use debugging mode to check how the registers change

#include "stm32f4xx.h"
#define LED_PIN    5		//LD2
#define BUTTON_PIN 13


void RCC_HSI_init(void);   							//defined in ecRcc.h
void RCC_GPIOA_enable(void);
void RCC_GPIOC_enable(void);

int main(void) {	
	/* Part 1. RCC GPIOA Register Setting */
		RCC_GPIOA_enable();
		RCC_GPIOC_enable();
		
	/* Part 2. GPIO Register Setting for OUTPUT*/			
		// GPIO Mode Register
		GPIOA->MODER &= ~(3UL<<(2*LED_PIN)); // Clear '00' for Pin 5
		GPIOA->MODER |=   1UL<<(2*LED_PIN);  // Set '01' for Pin 5
		
		// GPIO Output Type Register  
		GPIOA->OTYPER &= ~(1UL<<LED_PIN);   	// 0:Push-Pull   
		
		// GPIO Pull-Up/Pull-Down Register 
		GPIOA->PUPDR  &= ~(3UL<<(2*LED_PIN)); // 00: none
		
		// GPIO Output Speed Register 
		GPIOA->OSPEEDR &= ~(3UL<<(2*LED_PIN));
		GPIOA->OSPEEDR |=   2UL<<(2*LED_PIN);  //10:Fast Speed
	
	
	/* Part 3. GPIO Register Setting for INPUT*/			
		// GPIO Mode Register
		GPIOC->MODER &= ~(3UL<<(2*BUTTON_PIN)); // 00: Input	 		
   
		// GPIO Pull-Up/Pull-Down Register 
		GPIOC->PUPDR &= ~(3UL<<(2*BUTTON_PIN)); 
		GPIOC->PUPDR  |= 2UL<<(2*BUTTON_PIN); 	// 10: Pull-down		    
	 
	 
	/* Part 4. Deal loop  */	
		while(1){
			unsigned int btVal=0;
			//Read bit value of Button
			btVal=(GPIOC->IDR) & (1UL << BUTTON_PIN);	
			if(btVal == 0)
				GPIOA->ODR |= (1UL << LED_PIN);	 		
			else
				GPIOA->ODR &= ~(1UL << LED_PIN); 
		}
}



void RCC_GPIOA_enable()
{
		// HSI is used as system clock         
		RCC_HSI_init();	
	
		// RCC Peripheral Clock for GPIO_A Enable 
		RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;
}

void RCC_GPIOC_enable()
{
		// HSI is used as system clock         
		RCC_HSI_init();	
	
		// RCC Peripheral Clock for GPIO_A Enable 
		RCC->AHB1ENR |= RCC_AHB1ENR_GPIOCEN;
}


void RCC_HSI_init() {
	// Enable High Speed Internal Clock (HSI = 16 MHz)
  RCC->CR |= ((uint32_t)RCC_CR_HSION);

  // wait until HSI is ready
  while ( (RCC->CR & (uint32_t) RCC_CR_HSIRDY) == 0 ) {;}
	
  // Select HSI as system clock source 
  RCC->CFGR &= (uint32_t)(~RCC_CFGR_SW); 									
  RCC->CFGR |= (uint32_t)RCC_CFGR_SW_HSI; 				
			
	// Wait till HSI is used as system clock source
  while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != 0 ); 
}

Software vs Hardware Debug

• There are two methods to debug your program: software debug and hardware debug.

  • Software Debug: you do not need to connect the MCU to PC to debug a software program.

  • Hardware Debug: MCU board must be connected to the computer.

• For this tutorial, we will use Hardware Debugging.

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Debug Control

Compile, Debug, and Run

• You can program the STM32 flash by clicking the LOAD button .

• Click the debug button to start the debug and click it again to exit the debug.
• You can use the breakpoint button to set a break point in either disassembly or source windows.
• STM32 allows up to six breakpoints during hardware debugging. When a program stops at a breakpoint, the corresponding instruction has not been executed yet.

• You can choose either debugging assembly code or C-code line by choosing the disassembly or source window in focus.

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• Control buttons of debugging

  

  image

  • Run (F5): Continues the execution from the current position until you click Stop or the program is paused by a breakpoint.

  • Step In (F11): Execute one step and enter the function if the current step calls a function.

  • Step Out (Ctrl + F11): Execute until the current function returns.

  • Step Over (F10): Execute one step and run the function all at once if the current step calls a function.

Pheripheral Registers

• Choose the menu: Peripherals ⟶ System Viewer

• View and update the control and data registers of all available peripherals

• Check Registers for GPIO Port A (PA5 for LED).

• Check the value of Output Data Register (ODR) ODR5 and LED status

• Check and uncheck ODR5 with mouse click and see how LED turns on/off

image

• Check Registers for GPIO Port C (PC_13 for Button B1).

• Check the value of Input Data Register (IDR) IDR13

• Keep pressing ‘F10’ while B1 button is pressing and unpressing. Check the value of IDR13.

• Now, check other peripheral registers such as RCC.

Processor Registers

Core Registers

• Program counter (PC) r15 holds the memory address (location in memory) of the next instruction to be fetched from the instruction memory.

• Stack point (SP) r13 holds a memory address that points to the top of the stack. SP is a shadow of either MSP or PSP.

• xPSR (Special-purpose program status registers) is a combination of the following three processor status registers:

  • Application PSR

  • Interrupt PSR

  • Execution PSR

xPSR	Description
N	Negative or less than flag (1 = result negative)
Z	Zero flag (1 = result 0)
C	Carry or borrow flag (1 = Carry true or borrow false)
V	Overflow flag (1 = overflow)
Q	Q Sticky saturation flag
T	Thumb state bit
IT	If-Then bits
ISR	ISR Number (6 bits)

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