is possible to use printf?

Where do you expect the data to go?

https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32Discovery/DispForm.aspx?ID=2606

I need to send data to the PC through the RS232, I do not need to receive from the PC but only print strings from the microcontroller to the PC, I need to use a function like

#include <
stm32f4_discovery.h
>
#include <
stdio.h
>

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_USART3); 

GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_USART3); 

USART_InitStructure.USART_BaudRate = 9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART3, &USART_InitStructure);
USART_Cmd(USART3, ENABLE);

it's all right but i I us printf(''hello''); the microcontrollers stops

#pragma import(__use_no_semihosting_swi)

//******************************************************************************
// Hosting of stdio functionality through USART3
//******************************************************************************
#include <
rt_misc.h
>
#pragma import(__use_no_semihosting_swi)
struct __FILE { int handle; /* Add whatever you need here */ };
FILE __stdout;
FILE __stdin;
int fputc(int ch, FILE *f)
{
while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET);
USART_SendData(USART3, ch);
return(ch);
}
int fgetc(FILE *f)
{
char ch;
while(USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == RESET);
ch = USART_ReceiveData(USART3);
return((int)ch);
}
int ferror(FILE *f)
{
/* Your implementation of ferror */
return EOF;
}
void _ttywrch(int ch)
{
while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET);
USART_SendData(USART3, ch);
}
void _sys_exit(int return_code)
{
label: goto label; /* endless loop */
}
/**************************************************************************************/

I'm sorry but I can not understand ...

The take away here is that by default it links in library code using SWI calls (Software Interrupts) to perform OS level functions. Functions you don't provide, and it consequently crashes, Hard Faults, whatever.

thanks

for your help

and

your kindness

!

I would like

to ask your advice

some time

ago

you suggested

''

Guide to the

ARM

Cortex-

but is

there 

a

similar

guide for the

M4

microcontroller

?

There isn't an M4 volume, but the M0 one is the newest and much thicker, to be honest they are covering a lot of the same material. So with the exception of the floating point unit they are all fairly similar. The M3 editions seem to exist fairly readily on the internet so I'd browse those first.

http://www.arm.com/products/processors/cortex-m/cortex-m4-processor.php

Actually the M0 book is only about 50pages longer.  It looks and feels much ''thicker'', because the paper used in the M0 book is of a heavier stock.  I wish they had used the same thinner paper that was used on the M3 book though.

Since this thread started, Joseph Yiu has a book covering the M3/M4

http://www.amazon.com/Definitive-Cortex%C2%AE-M3-Cortex%C2%AE-M4-Processors-Edition/dp/0124080820

http://www.amazon.com/Designers-Guide-Cortex-M-Processor-Family/dp/0080982964