Removing useless variables turns a unworking code to a working code.

[JulienD]

Posted on October 26, 2015 at 14:30

Hi

Some days ago I tried to add a PWM function in my project, As it was unsuccessfull, I built a working standalone pwm project that I tried to integrate to the real life project. I did not succeed in making it work. To understand what happens, I removed every piece of code to get a minimum non working project. Now I face some very stranges behaviours : - removing one or several unused uint16_t variables turns the unworking code to a working one. - inlining a function called once turns the unworking code to a working one. - replacing a call to function A which only do a call to function B by a direct call to function B turns the unworking code to a working one. I really don't unerdstand what happens. If anybody has an idea of what may happen, I'm interested in any clue. Optimization is -O0. µc : STM32F103VET6. Code attached and below. Search for ''***'' pattern to find comments that points the above lines of code. main.c

#include 

#include ''board.h''


int
main( 
void
)

{

// board_timer_init();

board_init_mcu(); 
// *** calling the previous commented function instead of this one makes the code work.

RightTimerLedStart( );

while
( 1 )

{

}

}

board.h

#ifndef SRC_BOARD_H_

#define SRC_BOARD_H_


#include 

#include 

#include 

#include ''stm32f10x.h''

#include ''timer_board.h''




/*!

* Board GPIO pin names

*/

typedef 
enum

{

PA_0 = 0, PA_1, PA_2, PA_3, PA_4, PA_5, PA_6, PA_7, PA_8, PA_9, PA_10, PA_11, PA_12, PA_13, PA_14, PA_15,

PB_0, PB_1, PB_2, PB_3, PB_4, PB_5, PB_6, PB_7, PB_8, PB_9, PB_10, PB_11, PB_12, PB_13, PB_14, PB_15,

PC_0, PC_1, PC_2, PC_3, PC_4, PC_5, PC_6, PC_7, PC_8, PC_9, PC_10, PC_11, PC_12, PC_13, PC_14, PC_15,

PD_0, PD_1, PD_2, PD_3, PD_4, PD_5, PD_6, PD_7, PD_8, PD_9, PD_10, PD_11, PD_12, PD_13, PD_14, PD_15,

PE_0, PE_1, PE_2, PE_3, PE_4, PE_5, PE_6, PE_7, PE_8, PE_9, PE_10, PE_11, PE_12, PE_13, PE_14, PE_15,

PF_0, PF_1, PF_2, PF_3, PF_4, PF_5, PF_6, PF_7, PF_8, PF_9, PF_10, PF_11, PF_12, PF_13, PF_14, PF_15,

PH_0, PH_1, PH_2, PH_3, PH_4, PH_5, PH_6, PH_7, PH_8, PH_9, PH_10, PH_11, PH_12, PH_13, PH_14, PH_15,

// Not connected

NC = ( 
int
)0xFFFFFFFF

} PinNames;



/*!

* Define the GPIO IRQ on a rising, falling or both edges

*/

typedef 
enum

{

NO_IRQ = 0,

IRQ_RISING_EDGE,

IRQ_FALLING_EDGE,

IRQ_RISING_FALLING_EDGE

} IrqModes;


/*!

* Define the IRQ priority on the GPIO

*/

typedef 
enum

{

IRQ_VERY_LOW_PRIORITY = 0,

IRQ_LOW_PRIORITY,

IRQ_MEDIUM_PRIORITY,

IRQ_HIGH_PRIORITY,

IRQ_VERY_HIGH_PRIORITY

} IrqPriorities;


/*!

* Structure for the GPIO

*/

typedef 
struct

{

PinNames pin;

uint16_t pinIndex;

GPIO_TypeDef *port;

uint16_t portIndex;

} Gpio_t;




#define RIGHT_BLUE_LED PA_9


extern
Gpio_t right_blue_led;


void
board_init_mcu( 
void
);

void
board_timer_init( 
void
);


/*!

* \brief Initializes the given GPIO object

*

* \param [IN] obj Pointer to the GPIO object to be initialized

* \param [IN] pin Pin name ( please look in pinName-board.h file )

* \param [IN] mode Pin mode (This parameter can be a value of @ref GPIOMode_TypeDef)

* \param [IN] value Default output value at initialization

*/


void
gpio_init( Gpio_t *obj, PinNames pin, GPIOMode_TypeDef mode);



#endif /* SRC_BOARD_H_ */

board.c

#include ''board.h''


Gpio_t right_blue_led;


void
board_init_mcu( 
void
)

{

board_timer_init();

}


void
board_timer_init( 
void
)

{

TimersLedsInit();

}


void
gpio_init( Gpio_t *obj, PinNames pin, GPIOMode_TypeDef mode)

{

GPIO_InitTypeDef GPIO_InitStructure;


if
( pin == NC )

{

return
;

}


obj->portIndex = ( uint32_t ) pin >> 4;


obj->pin = pin;

obj->pinIndex = ( 0x01 << ( obj->pin & 0x0F ) );


obj->port = ( GPIO_TypeDef * )( GPIOA_BASE + ( obj->portIndex << 10 ) );

RCC_APB2PeriphClockCmd( ( RCC_APB2Periph_GPIOA << obj->portIndex ), ENABLE );


GPIO_InitStructure.GPIO_Mode = mode;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Pin = obj->pinIndex;

GPIO_Init( obj->port, &GPIO_InitStructure );

}

timer_board.h

#ifndef SRC_TIMER_BOARD_H_

#define SRC_TIMER_BOARD_H_


#include  /* C99 types */


void
TimersLedsInit();

void
RightTimerLedStart( );


#endif /* SRC_TIMER_BOARD_H_ */

timer_board.c

#include  /* C99 types */

#include 

#include ''board.h''



void
TimersLedsInit()

{

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;


/* Time base configuration */

TIM_TimeBaseStructure.TIM_Prescaler = 56000;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseStructure.TIM_Period = 1000;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;


/* TIM1 clock enable */

RCC_APB2PeriphClockCmd( RCC_APB2Periph_TIM1, ENABLE );


/* Time base configuration */

TIM_TimeBaseInit( TIM1, &TIM_TimeBaseStructure );


TIM_Cmd( TIM1, DISABLE );

}


/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */


void
RightTimerLedStart( )

{

gpio_init( &right_blue_led, RIGHT_BLUE_LED, GPIO_Mode_AF_PP ); 
// *** Changing this line by the following paragraph (which is the inline equivalent) makes the code work.


// GPIO_InitTypeDef GPIO_InitStructure;

// RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA , ENABLE );

// GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

// GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

// GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

// GPIO_Init(GPIOA, &GPIO_InitStructure );


uint16_t CCR1_Val = 500;

uint16_t CCR2_Val = 249; 
// *** Removing this unused variable makes the code work.

uint16_t CCR3_Val = 166; 
// *** Removing this unused variable makes the code work.



/* PWM1 Mode configuration: Channel1 */

TIM_OCInitTypeDef TIM_OCInitStructure;

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = CCR1_Val;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;


TIM_OC1Init( TIM1, &TIM_OCInitStructure ); 
// *** removing this (useless) line makes the code work.

TIM_OC2Init( TIM1, &TIM_OCInitStructure );


TIM_ARRPreloadConfig( TIM1, ENABLE );


/* TIM3 enable counter */

TIM_Cmd( TIM1, ENABLE );


TIM_CtrlPWMOutputs( TIM1, ENABLE );

}

#stm32f103-pwm

[Danish1]

Posted on October 26, 2015 at 14:52

Maybe you haven't allocated enough space for the stack.

Hope this helps,Danish

[qwer.asdf]

Posted on October 26, 2015 at 14:57

[deleted] as Danish Ali was faster 😉

[JulienD]

Posted on October 26, 2015 at 16:16

Hi,

Thanks for your answer. Where do you find this information ? I had a look to the startup and link files but this was not obvious to me... Julien