Problem with scanf in STM32F4, it is scanning only the first char even I am requesting to scan an int or float. Details in description

[bassem.saleh93]

here is the code I am using to scan

int ScanConfig(__const char * format, va_list args) {
 unsigned i=0;
 char ch = 0;
 char buffer[256];
 int ret = 0;
 while((i<sizeof(buffer))&&(ch!='\n')&&(ch!='\r')){
 HAL_StatusTypeDef status = HAL_TIMEOUT;
 while (status == HAL_TIMEOUT) {
 status = HAL_UART_Receive(&UartHandle1, (uint8_t *)&ch, 1, HAL_MAX_DELAY);
 if (status == HAL_TIMEOUT) {
 /*HAL_UART_DeInit(&rxHandle);
 HAL_UART_Init(&rxHandle);*/
 }
 else
 break;
 }
 
 buffer[i]=ch;
 i++;
 ret = vsscanf(buffer, format, args);
 if (ret > 0)
 break;
 }
 buffer[i]=0;
 return ret;
}
int Scan(__const char * format, ...) {
 va_list args;
 va_start(args, format);
 int size = ScanConfig(format, args);
 va_end(args);
 return size;
}

I am calling the function like this:

Scan("%f",&InVar);

The problem that if I try to enter 4.5 for example, I can't and it saves only 4.

[Tesla DeLorean]

Which tools/libraries are you using? Are floating point libraries for printf()/scanf() included, or lightweight alternatives?

Do you properly NUL terminate the buffer before calling vsscanf() ? Do you, or should you, clear the buffer[] as it is a local/auto variable holding whatever junk is currently on the stack.

[bassem.saleh93]

I am using HAL library on Eclipse IDE. Yes, floating point is included for printf and scanf. The problem is not that it does print or scan garbage. The problem that it just scans one character.

[Tesla DeLorean]

Does it actually fill the buffer?

As I already noted you need to NUL terminate the buffer.

Otherwise, perhaps step with the debugger to understand why it is finishing the scan early.