line feed for printf("\n some text")

[mgiaco]

Hi,

Today I made at first test on my stm32 board with your lib. First impression works great an compiles without any warning on gnu_arm_gcc 5.x

One usage question... normaly I use :

printf("\nHallo Welt");

if I would like to print something at the beginning of a new line. But with your implementation I do also need some additional line feed - otherwise the line does not start at position 0 on a terminal:

printf("\n\rHallo Welt");

So I am wondering if the _printchar should handles this is the printf implementation responsible for that?

many thanks

[mpaland]

Hello @mgiaco ,
printf is just the string "transporter" for sprintf, which writes the formatted text to a given buffer.
So printf creates its own temp buffer of PRINTF_BUFFER_SIZE size, formats the given text and calls _putchar() char by char for output.
Any text without the format specifier (%) is copied directly into the output (string) like\n \r etc.

_putchar and printf have no idea how your terminal looks like. Some terminals just need a CR, others (like yours) need a CRLF to go the next line.
As you suspected, this is (normally) all handled in your custom _putchar() routine.
Something like:

void _putchar(char character)
{
  if (character == '\n') {
    send('\n');
    send('\r');
  }
  else {
    send(character);
}

send() is your terminal/serial/whatever output here.
Other terminals may need a translation to ESC sequences or something else...

Same if you implement \t \v tab support. If _putchar() processes this sequence you have to move the cursor to the next horizontal or vertical tab position with the emulation codes you use.

[mgiaco]

okay many thanks.