I'm trying to pack together a bunch of surplus cel-phone LCD's with 690s and
make a generic serial display so cheap that I can instrument
anything/everything.  Since I don't know in advance exactly what character
set I can get away with it makes sense to err on the side of completeness.

So that means upper and lower case and a basic set of punctuation, which
gets us slightly past the 256 limit.  I was thinking there could be some
sort of clever compression that you could decode coming out of the table to
avoid the need for varying lengths and lookup tables.

The truth is I haven't figured out how to deal with tables that cross
boundaries yet, so I thought if I could push it up into EEPROM I could avoid
the inevitable a bit longer...

But no :-)

Thanks for again your help and input,

DougM

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
William "Chops" Westfield
Sent: Wednesday, April 02, 2008 9:10 PM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC]: EEPROM on the 16F690


On Apr 2, 2008, at 4:20 PM, Doug Metzler wrote:
> has anyone successfully compressed a complete 5*7 LCD font into 256  
> bytes of EEPROM?

I've thought about it, especially since tables bigger than 256bytes  
can be such a pain. (but are you sure you want it in eeprom rather  
than flash?)

You have 35 bits per character.  It's probably not worthwhile trying  
to do that in less than 5 bytes, so the obvious encoding lets you  
have 51 characters.  There are 94 characters generally considered  
printable.  68 if you eliminate lower case.  The "squoze" character  
set (old-style symbol characters: 6 chars in 32 bits) has 40  
characters.  So squoze fits with no problems.  What do you consider  
complete? Nine characters might be considered to have a width of 1,  
and in general quite a few might have a width lower than 5, but then  
you have some sort of two-stage lookup and that takes up space  
elsewhere...
So I think I'd conclude that you can fit a USEFUL font subset in 256  
bytes pretty easily, but probably not a "complete" font...

BillW

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