Tom McGahee wrote:
>Paul,
>You are right. 'f' and 'F' are the same. Lower case characters are
>always a bit difficult. 'D' is identical to 'O'. 'A' is the same as 'R'. Yet
>the human mind can often distinguish the correct letter by the
>*context* in which it is used.
>
>Upper case looks best. In the examples
>below, most people have no difficulty reading 'DANGER' instead of
>'OANGER', and 'UPPER CASE ONLY' instead of 'UPPEA CRSE ONLY'. In this case,
>the 'R' and 'A' have the same shape, but are properly distinguished by
>most people. The mind will boggle at things like 'DOODAR', because it has
>no clues, and the identical letters are adjacent.
> _  _  _  _  _  _
>| ||_|| ||_ |_ |_|
>|_|| || ||_||_ | |
>
>    _  _  _  _   _  _  _  _   _  _
>| ||_||_||_ |_| |  |_||_ |_  | || ||  |_|
>|_||  |  |_ | | |_ | | _||_  |_|| ||_  _|
>
>There is more to this 'than meets the eye'. The brain is an
>amazing thing!

I disagree and to test out my feeling I printed out the two examples from
your note and passed it around to a few people at work.  After a few
seconds, some people figured out the first one was "danger", but nobody
really got the the second example in less than thirty seconds.

Nobody I talked to felt the quality of this was good enough for using with
somebody that's not familiar with this type of character set.


About twenty years ago, TI came up with a character set for using a seven
segment display which is actually a lot better for most characters.  Using
it, the examples above become:

>    _     _  _
> _||_| _ |_ |_  _
>|_|| || ||_||_ |
>
>    _  _  _      _  _     _   _
>   |_||_||_  _  |  |_| _ |_  | | _ |  |_|
>|_||  |  |_ |   |_ | | _||_  |_|| ||_  _|

Which is only marginally better and still requires the user to understand
the character set (Note what happened to "s" so that it can be
differentiated with "5").  Other problem characters include "K", "M", "N",
"Q", "T", "V", "W", "X" and "Z".

I guess using a character set like this on a seven segment display is
acceptable if the developer is the only person using it, but otherwise I
would never consider using it.

If you want to output characters, you should look at a 16 segment LED
display (which is designed for alpha-numerics) or, even better, use an LCD
display (which will probably end up being cheaper and easier to wire).

myke

PICLite has been upgraded!  Check out version 2.00a at:

http://www.myke.com/piclite

PICLite now includes a Macro Processor that allows structured programming
language constructs ("if/else/end", "while/end" and "for/end").

Look in on the life of the Rabitte family in Dublin; Roddy Doyle's
"Barrytown Trilogy" in the Book Room this week,

http://www.myke.com/Book_Room