Posted on November 14, 2011 at 11:51 Hello Forum!
While trying to retarget the printf() and scanf() functions, with printf everything worked well.
However, with scanf occured a weird problem.
First here are the overwrited low-level functions :
size_t __write(int handle, const unsigned char * buffer, size_t size)
{
size_t nChars = 0;
if (buffer == 0)
{
/*
* This means that we should flush internal buffers. Since we
* don't we just return. (Remember, ''handle'' == -1 means that all
* handles should be flushed.)
*/
return 0;
}
for (/* Empty */; size != 0; --size)
{
while(!(USART1->SR & USART_FLAG_TXE));
USART1->DR = ((*buffer++) & 0x01FF);
++nChars;
}
return nChars;
}
size_t __read(int handle, unsigned char * buffer, size_t size)
{
int nChars = 0;
for (/* Empty */; size > 0; --size)
{
while(!(USART1->SR & USART_FLAG_RXNE));
int c = USART1->DR & 0x01FF;
if (c < 0)
break;
*buffer++ = c;
++nChars;
}
return nChars;
}
while (1)
{
scanf(''%i \n'',&iNumb);
printf(''%i\n'',iNumb);
}
I set a breakpoint into the __read-method() and I noticed something,I think that's the point:
Sending '1', the while-loop becomes true and the integer 'c' equals '1'. (Everythings fine)
The failure is, that the program jumps a second time into the function and get stuck in the while-loop because there's no second character. The result is : sending a second character, the first one is displayed and so on...
For better understanding, here's the Terminal output:
1
2
Echo from STM32: 1
3
Echo from STM32: 2
4
Echo from STM32: 3
5
Echo from STM32: 4
6
Echo from STM32: 5
7
Echo from STM32: 6
8
Echo from STM32: 7
10
Echo from STM32: 8
11
12
Echo from STM32: 1011
The behavior with two-digit numbers is a little different...
Hope you can help me with this one!
🙂 Thank you in advance!
Chris
