I haven't searched for a real documentation.
The mimimum what is always available is the sourcecode.
And in some cases the source-code is sufficient to use it as "documentation".
Though I admit that in most cases it is not sufficient to look into the sourcecode.
It would be convenient if there would be different functions for displaying values of different variable types.
For this looking in the sourcecode is promising.
finding the sourcecode online works like this
google for "Github" + your words of interest.
In your case the name of the used library
https://www.google.de/search?as_q=github+Adafruit_LEDBackpack.h
which quickly finds the GiPo (my short for Github repository)
and there you look up the file Adafruit_LEDBackpack.h
/Adafruit_LEDBackpack.h
and voila inside this file you find all the defined functions which include
void printFloat(double n, uint8_t fracDigits = 2, uint8_t base = DEC);
by searching for "float" you will find all functions that deal - somehow - with floats
and you will find
/*!
@brief Print double-precision float value to 7-segment display.
@param n Numeric value.
@param digits Fractional-part digits.
*/
void print(double n, int digits = 2);
this gives a rough oveview how to use these functions.
well if you give a typical example of how the numbers look like the users here can make suggestions how you can code this.
This is something newcomers seems to need a very long time to understand:
coding starts with normal words / normal numbers
in the sense of writing down in normal words - and by avoiding any progamming/coding-terms
The answer to the question: What is the desired functionality?
In your case:
showing numbers like
-123456789.123456
on a 16-digit 14-segment-display
As the 16 digit display is divided into 4 4digit displays the complete number has to be separated into
-123
4567
89.12
3456
Programming this is a step by step process.
convert the float into an array of char because in an array of char each digit is easier to access.
It might be that you don't know yet what arrays of chars are.
So you just do a coding-interrupt learning arrays of char
I recommend this learning by using small testprograms that do just a few things
like setting up a easy to analyse demofloat like
-123.4567
and then coding convert example float to a array of char and print the array of char
to test if it works like it should
next step coding a function that takes each digit and put the digit into its group
You will hav to test this functions with all numbers that can occur
0
0.1
-0.1
0.0000000001
-0.0000000001
12.3
-12.3
etc.
step by step learning how to modify the code so the final code can deal with all numbers correctly.
In this process whenever you don't understand anything you ask it here in the forum by providing each time a complete test-sketch and its serial output.
I'm sure that this kind of questions is enjoyable to answer to quite a lot of users.
depending on the minimum and the maximum numbers you need the solutions look different.
So it is up to you to define the smallest value and how this smallest number schould appear on your display and defining the biggest value and how this biggest value shall be shown on your display
best regards Stefan