Retargeting printf under SEGGER Embedded Studio

[mcn]

Hi all,

I'm currently trying to get the UART example (no SoftDevice) to work under Segger Embedded Studio. What I know is, that retarget.c is used to redefine the neccesary functions for printf (stdio).

app_uart_get and app_uart_put work absolutely fine. However, printf is not working. Compiling the example in Embedded Studio results in the following errors:

storage size of '__stdout' isn't known storage size of '__stdin' isn't known

Commenting the FILE __stdout and FILE __stdin lines out gets compilation running however printf doesn't work.

Does anyone can help me with that?

Thank you!

Martin

[Jørgen Holmefjord]

Hi,

The file retarget.c only contains redefinition of the stdio functions for ARM and GCC libraries. It is not supported by Segger Embedded Studio. Have a look at this page about how you can customize the output of putchar in SES.

Best regards,

Jørgen

[mcn]

Thank you for your answer!

This is the solution:

1. Do not use the website, since there are minor mistakes in the code. Use this: www.segger.com/.../EmbeddedStudio_v310i_manual.pdf
2. This is the easiest way: a) Include stdarg.h

b) Define a function:

void uart_printf(const char *fmt, ...)
{
    char buf[80], *p;
    va_list ap;
    va_start(ap, fmt);
    vsnprintf(buf, sizeof(buf), fmt, ap);
    for (p = buf; *p; ++p)
    app_uart_put(*p);
    va_end(ap);
 }

c) Use this function, done :)

Best regards

[RichieJH]

I just faced the same issue after commenting out FILE __stdout and FILE __stdin and couldn't quite get Jorgen's response to work.

Anyway I found an even quicker way, and that is to convert printf to SEGGER_RTT_printf(0, String). So printf("\r\nUART Start!\r\n") becomes SEGGER_RTT_printf(0, "\r\nUART Start!\r\n"). Just ensure you have SEGGER_RTT_printf.c in your project. Thought I would mention this in case other users of SES come across this issue.

[MattyIce]

@RichieJH, did you exclude retarget.c from the project, in addition to replacing printf() w/ SEGGER_RTT_printf()?