I come across a problem when trying to run this code in order to blink the built-in LED (located at PC13) on the blue pill board (STM32F103C8, ARM Cortex M3):
#include "stm32f10x.h" // Device header
#define max 1000000
int main(void){
RCC->APB2ENR |= 1<<4;
GPIOC->CRH &= 0xFF0FFFF;//clear the necessary bit
GPIOC->CRH |= 0x00300000;//set the necessary bit
GPIOC->ODR &= ~(1<<13);//turn PC_13 ON
while(1){
GPIOC->ODR |= 1<<13;//off
for(unsigned int i = 0;i < max;++i);
GPIOA->ODR &= ~(1<<13);//on
for(unsigned int i = 0;i < max;++i);
}
}
.
Here I receive some errors and I don't know why:
Could anybody help me? Also, when I declare the unsigned integer "i" within the while loop all goes fine, but even though, nothing happens, the LED still does not blink. Here is the modified code:
#include "stm32f10x.h" // Device header
#define max 1000000
int main(void){
RCC->APB2ENR |= 1<<4;
GPIOC->CRH &= 0xFF0FFFF;//clear the necessary bit
GPIOC->CRH |= 0x00300000;//set the necessary bit
GPIOC->ODR &= ~(1<<13);//turn PC_13 ON
while(1){
unsigned int i;
GPIOC->ODR |= 1<<13;//off
for(i = 0;i < max;++i);
GPIOA->ODR &= ~(1<<13);//on
for(i = 0;i < max;++i);
}
}
. Moreover, I tried another trick, to declare the integer "i" outside the loop, like here:
#include "stm32f10x.h" // Device header
#define max 1000000
int main(void){
RCC->APB2ENR |= 1<<4;
GPIOC->CRH &= 0xFF0FFFF;//clear the necessary bit
GPIOC->CRH |= 0x00300000;//set the necessary bit
GPIOC->ODR &= ~(1<<13);//turn PC_13 ON
unsigned int i;
while(1){
GPIOC->ODR |= 1<<13;//off
for(i = 0;i < max;++i);
GPIOA->ODR &= ~(1<<13);//on
for(i = 0;i < max;++i);
}
}
. Then, I've received the next error message:
. Now, the question is why?
Please help me.
In the uVision project configuration dialog C/C++ tab, select "use C99".
ISO C90 dies not allow declaration of variables in either a for
statement or following non -declaritive code in a statement block.
Alternatively move the declaration to the top of the statement block in which it is required. Better to use C99 though - it has been around long enough to be regarded as lowest common denominator standard I think!