How can I write with all the characters from the ascii table? (0x20 -> 0xFF)
This depends on what and why you doing this:
1. The MD_MAX72XX_Test example shows what is defined for all the characters as part of its normal cycle.
2. Font Builder will let you view what the characters look like and edit them.
3. Non-printable characters can be put in a string or character constant using the usual escape sequence normal for C/C++ - "\x0NN" - where \ is the escape, x indicates hex and then the next three hex digits are the ascii code for the character (eg, \x0a4 for Ascii 0xa4). There are others forms of this so best to look it up.
4. Printable characters are just put in a string or character as normal.