Supported Format Specifiers

Arduino Platform Supported Specifiers

Because all Arduino cores for all Arduino compatible boards don't unanimously support printf, we have a basic imitation mechanism included with RF24LogPrintfParser.

The format specifiers' usage:

%[flags][pad_quantity][.precision_quantity]specifier

The following list of characters that follow a % symbol (or a flag/pad_quantity/precision_quantity option) will signify that the corresponding argument is of a certain datatype.

Specifier	Representation
F / D	a double
s / S	a string
d / i	a signed integer
du / iu / u / lu / hu	an unsigned integer
x / X	an unsigned hexadecimal integer
o	an unsigned octal integer
b	an unsigned binary integer
c	a single character
%	escapes a single character

Limitations

These are the differences to standard printf parsing and our in-house printf parsing:

• Floats/doubles will only use the precision_quantity as the number of decimal places. Specifying a pad_quantity for padding the whole numbers of floats/doubles is not supported (thus the pad_quantity has no affect on floats and doubles).
• Only the Arduino AVR platform supports a string (from flash memory) specifier's capitol (S) syntax because of the special __FlashStringHelper implementation. All other platforms support using s for strings.
• The only supported flags are zero (0) for padding data with zeros instead of spaces. Other flags (+, -, ) have no affect.
• The u character will enforce numeric data to be interpreted as an unsigned long number. Otherwise, all numeric data is represented as a signed long number (float and double variables are represented as a double).

Padding the numbers

For each numeric data specifier, a quantity of padded characters can be designated before the specifer (but immediately after the % symbol). The default character used for padding is a space (), but putting a zero (0) character flag before the padding_quantity changes the padding character to zeros (0).

For example:

const char vID[] = "specifier fmt";
RF24Log_info(vID, "0x%02x %%", 0xf); // prints:     60176; INFO  ;specifier fmt;0x0F %
RF24Log_info(vID, "%4x", 0xa0);      // prints:     60178; INFO  ;specifier fmt;  A0
RF24Log_info(vID, "%.2F", 3.1459);   // prints:     60180; INFO  ;specifier fmt;3.14
RF24Log_info(vID, "%.4F", 2.71);     // prints:     60182; INFO  ;specifier fmt;2.7100