prints a 2 character string on the 7-segment display
Supported characters are in the group [-_ 0-9ACE-JLPRUXb-dhnoru] (contains space). Read this article for possible representations of these characters. Two characters of the set should never have the same representation.
- Parameters:
-
| str | the 0-terminated string |
- Returns:
- 0 on success, negative value on error
- Return values:
-
| 0 | success |
| -1 | character at position 0 not printable |
| -2 | character at position 1 not printable |
| -3 | both characters not printable |
| -4 | str is an empty string |