Posted by flavio.renga on 2017-05-10 10:25

What about retargeting getchar() function?

My simple goal is, for the moment, to wait until the ‘p’ key is pressed on the PC console.
I’m having problem with it...

Infact, I’ve tried to retarget the getchar() function in the same way I’ve done for the printf() function, but without success.

If I use directly the HAL_UART_Receive() function, all is right.
If I try redefining the io_getchar(void), function, I get problems.

---------------

Hereafter the working code:

> // Wait for ‘p’ char pressed
> HAL_UART_Receive (&huart3, (uint8_t *)&c, 1, 0xFFFF);
> while (c != ‘p’) {
> HAL_UART_Receive (&huart3, (uint8_t *)&c, 1, 0xFFFF);
> }

---------------

Instead, if I use the following code, the program stucks into the GETCHAR_PROTOTYPE routine:

> #ifdef GNUC
> /* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf
> set to ‘Yes’) calls __io_putchar() */
> #define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
> #define GETCHAR_PROTOTYPE int __io_getchar(void)
> #else
> #define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
> #define GETCHAR_PROTOTYPE int fgetc(FILE *f)
> #endif /* GNUC */

...

> GETCHAR_PROTOTYPE {
> int ch;
> HAL_UART_Receive (&huart3, (uint8_t *)&ch, 1, 0xFFFF);
> return ch;
> }

...

> // Wait for ‘p’ char pressed
> c = getchar();
> while (c != ‘p’) {
> c = getchar();
> }

In particular, the char is correctly captured by HAL_UART_Receive (I can see the char by using the breackpoints), but the GETCHAR_PROTOTYPE repeats infinitely without exiting and the while loop is never reached.

What is wrong with the code?

Thanks in advance!

Flavio