Posted on October 02, 2016 at 18:37Hi Marco,
For most development environments, adding a callback function that performs the _write() function, which would normally be provided by an OS, will make printf() work for you.
you can Google _write() for more information. The function and its parameters look like this:
int _write(int FD, char *buffer, int len){
HAL_UART_Transmit(&huart2, (uint8_t*)buffer, len, 1000);
return len;
}
where the first parameter is a handle for the output device being used, in this case since there is only one output device- the console, you can ignore this. It then passes a pointer to the formatted string it has prepared to output, and the length of the string. The function is of type int and expects the number of characters successfully written to be returned at the end of the function. The above clip fulfills all of these needs and uses a HAL call to output the string to your UART (change the uart reference if you are using a different one).
Also, in some tool chains this function is prefixed with two underscores, rather than one. The above example works with SW4STM32. I believe that the EWARM toolchain wants two underscores. In some environments you will get additional link errors for other OS functions like _sbrk() which may be needed as well, but if you are using CubeMX for your init code I think this will generally not be a problem.
Good luck,
Aaron
