Delay implementation in STM32 using for loop - embedded

Question

I am using a NUCLEO-L476RG development board,
I am learning to write GPIO drivers for STM32 family
I have implementing a simple logic in which I need to turn on an LED when a push button is pressed.
I have a strange issue:
Edit 1:The Bread board LED turns ON when the line temp=10 is commented, it doesn't turn ON when the delay issue called. Assuming if I add any line of code into that while loop the LED does not turn ON
The Bread board LED turns ON when the delay() function is commented, it doesn't turn ON when the delay issue called.
What could be the issue?
I have powered the board using the mini usb connector on the board, and the clock is configured at MSI with 4MHz
#define delay() for(uint32_t i=0; i<=50000; i++);
int main(void)
{
GPIO_Handle_t NucleoUserLED,NucleoUserPB,BreadBoardLED,BreadBoardPB;
uint8_t inputVal,BBinpVal;
uint32_t temp;
//User green led in the nucleo board connected to PA5
NucleoUserLED.pGPIO = GPIOA;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_5;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_OP;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinOpType = GPIO_OP_TYPE_PP;
//User blue button in the nucleo connected to PC13
NucleoUserPB.pGPIO = GPIOC;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_13;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_IP;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
//User led in the bread board connected to PC8
BreadBoardLED.pGPIO = GPIOC;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_8;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_OP;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinOpType = GPIO_OP_TYPE_PP;
//User DPDT connected in the breadboard connected to PC6
BreadBoardPB.pGPIO = GPIOC;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_6;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_IP;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_PU;
GPIO_PeriClkCtrl(GPIOA, ENABLE);
GPIO_PeriClkCtrl(GPIOC, ENABLE);
GPIO_Init(&NucleoUserLED);
GPIO_Init(&NucleoUserPB);
GPIO_Init(&BreadBoardLED);
GPIO_Init(&BreadBoardPB);
while(1)
{
/*****************************************************************
* Controlling the IO present in the nucleo board *
*****************************************************************/
inputVal = GPIO_ReadInputPin(NucleoUserPB.pGPIO, NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinNumber);
BBinpVal = GPIO_ReadInputPin(BreadBoardPB.pGPIO, BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinNumber);
if(inputVal == 0)
{
GPIO_ToggleOutputPin(NucleoUserLED.pGPIO, NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinNumber);
}
/*****************************************************************
* Controlling the IO present in the bread board *
*****************************************************************/
if (BBinpVal == 0 )
{
GPIO_WriteOutputPin(BreadBoardLED.pGPIO, BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber, 1);
}
else
{
GPIO_WriteOutputPin(BreadBoardLED.pGPIO, BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber, 0);
}
delay();
}
return 0;
}

Answer 1

It is not a function only the macrodefinition.
Your loop is likely to be optimized out
define it as
void inline __attribute__((always_inline)) delay(uint32_t delay)
{
while(delay--) __asm("");
}
Bear in mind that 50000 can be quite long if you run on low clock settings.

Answer 2

Not sure what the issue is because "it is not working" is not very specific.
However there are "quality" issues:
That is an inappropriate use of a macro - there is no benefit over using a function. The function call overhead argument does not hold - it is a delay, it is supposed to take time!
The empty-loop counter is not declared volatile - the compiler at any optimisation level other then the minimum is likely to remove the loop altogether.
A for-loop for a delay is a crude and generally non-deterministic solution, with a period that will change between compilers, with different compiler options and on different targets or with different clock speeds. STM32 is a Cortex-M device and given that you should use the SYSTICK counter for this. For example, as a minimum something like:
volatile uint32_t tick = 0 ;
void SysTick_Handler(void)
{
tick++ ;
}
void delayms( uint32_t millisec )
{
static bool init = false ;
if( !init )
{
SysTick_Config( SystemCoreClock / 1000 ) ;
init = true ;
}
uint32_t start = tick ;
while( tick - start < millisec ) ;
}

Answer 3

The issue was solved by declaring the iterator as a global variable. Now the LED turns on when the Push button is pressed
Previous implementation
#define delay() for(uint32_t i=0; i<=50000; i++);
Working implementation
uint32_t temp;
void delay(void)
{
for(temp = 0;temp<=50000;temp++)
{
;
}
}
Can any one tell me how declaring the variable as global solves the issue?
Find the working implementation below
#include <stdint.h>
#include "stm32l476xx.h"
#include "stm32l476xx_gpoi_driver.h"
#if !defined(__SOFT_FP__) && defined(__ARM_FP)
#warning "FPU is not initialized, but the project is compiling for an FPU. Please initialize the FPU before use."
#endif
uint32_t temp;
void delay(void)
{
for(temp = 0;temp<=50000;temp++)
{
;
}
}
int main(void)
{
GPIO_Handle_t NucleoUserLED,NucleoUserPB,BreadBoardLED,BreadBoardPB;
volatile uint8_t inputVal,BBinpVal;
//User green led in the nucleo board connected to PA5
NucleoUserLED.pGPIO = GPIOA;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_5;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_OP;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinOpType = GPIO_OP_TYPE_PP;
//User blue button in the nucleo connected to PC13
NucleoUserPB.pGPIO = GPIOC;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_13;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_IP;
NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
//User led in the bread board connected to PC8
BreadBoardLED.pGPIO = GPIOC;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_8;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_OP;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_NO_PUPD;
BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinOpType = GPIO_OP_TYPE_PP;
//User DPDT connected in the breadboard connected to PC6
BreadBoardPB.pGPIO = GPIOC;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinNumber = GPIO_PIN_6;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinMode = GPIO_MODE_IP;
BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinPuPdControl = GPIO_IP_PU;
GPIO_PeriClkCtrl(GPIOA, ENABLE);
GPIO_PeriClkCtrl(GPIOC, ENABLE);
GPIO_Init(&NucleoUserLED);
GPIO_Init(&NucleoUserPB);
GPIO_Init(&BreadBoardLED);
GPIO_Init(&BreadBoardPB);
while(1)
{
/*****************************************************************
* Controlling the IO present in the nucleo board *
*****************************************************************/
inputVal = GPIO_ReadInputPin(NucleoUserPB.pGPIO, NucleoUserPB.GPIO_Pin_Cfg.GPIO_PinNumber);
BBinpVal = GPIO_ReadInputPin(BreadBoardPB.pGPIO, BreadBoardPB.GPIO_Pin_Cfg.GPIO_PinNumber);
if(inputVal == 0)
{
GPIO_ToggleOutputPin(NucleoUserLED.pGPIO, NucleoUserLED.GPIO_Pin_Cfg.GPIO_PinNumber);
}
/*****************************************************************
* Controlling the IO present in the bread board *
*****************************************************************/
temp = 10;
if (BBinpVal == 0 )
{
GPIO_WriteOutputPin(BreadBoardLED.pGPIO, BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber, 1);
}
else
{
GPIO_WriteOutputPin(BreadBoardLED.pGPIO, BreadBoardLED.GPIO_Pin_Cfg.GPIO_PinNumber, 0);
}
delay();
}
return 0;
}

Answer 4

The issue is solved,
There was an bug in the driver layer I have written
Whenever an GPIO is configured as Input, the registers related to Output for that GPIO pin should be set to their reset value or the driver should not implement the API related to the Output