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How to use printf() function with stm32cubeMX + sw4stm32

Forum|Forum|10 years ago
September 1, 2015
12 replies
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Posted on September 01, 2015 at 19:13

Hi to every one,

It's the first time that I use the STM32CubeMX + SWSTM32 to program a stm32f401RE board. I have done already some example project but I can't use the printf() function to communicate with a terminal ( Tera Term) on the PC. Somebody can explain me how I can do it?

Thank you in advance!!

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mile milestone

Visitor II

Posted on October 18, 2017 at 13:05

PLEASE ALLOW ME TO ADD DETAILS OF WHAT I'VE DONE, TESTED ON NUCLEO F401RET

1. Using CUBEMX, I configures USART 2 as my serial communication (set as Asynchronous) and let it (cubemx) generate all initilial files and folders

CUBEMX USART2 SETUP:

- Asynchronous

-Parameter Setting by Default, except Baud Rate is 115200

-NVIC Setting, uncheck the UART global interrupt

-Did not touch the rest

- Finally, hit the Generate Code Icon !!

2. Opening the project with AC6 Workbench we should see something like this

3. NOW LET'S DO THE ADDITIONAL CODES AND SOME STEPS

Step 1 Let's add the following two function in our main.c - you can place them above the main() function

in my case i paste it on /* USER CODE BEGIN PV */ see highlighted

#ifdef __GNUC__

#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)

#else

#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)

#endif /* __GNUC__ */

PUTCHAR_PROTOTYPE

{

HAL_UART_Transmit(&huart2, (uint8_t *)&ch, 1, 0xFFFF);

return ch;

}

see pic below

Step 2 : Modify the linker flag in the project properties.

2.1 Go to Menu: Project\Properties\

2.2 Expand C\C++ Build on left pane, select Settings

2.3 On middel expand MCU GCC Linker drop down menu, and select Miscellaneous

2.4 Now on the rightside you can see the the ''Linker Flag'' text box.

2.5 Replace/update the text to

-specs=nosys.specs -specs=nano.specs -u _printf_float

Hit Ok

Step 3: Locate the file ''

syscalls.c

'' and place it on startup folder i.e. together with

startup_stm32f401xe.s

It should appear in the ''project explorer'' under ''startup'' folder

I found syscall.c in the repository of example folder of CubeMX . i.e. C:\Users\My\STM32Cube\Repository\STM32Cube_FW_F4_V1.16.0

STEP 4: I did check on STM32F401RETx_FLASH.ld file (on file exporer, its the file on the last - see picture) as suggest in the comment above and it is

0x20018000 by default so i leave it as is.

/* Highest address of the user mode stack */

_estack = 0x20018000; /* end of RAM */