Store and print string-constants

[Ted]

There was already a discussion in the past, but I couldn?t
find it in the archive.

Question:
printf("string_constant1")
printf("string_constant2")
uses too much rom.

What is the best methode to print constant strings without
too much rom usage?

Thanks TED
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[Steve H.]

I searched "String Rom" for 300 days back.

See the link...
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[R.J.Hamlett]

:=I searched "String Rom" for 300 days back.
:=
:=See the link...


Also, if the chip is one of the 18x family (where individual instruction memory locations can store two bytes), this code becomes unecessary, _but_ you can still save space quite massively by putting several messages into one table.
Something like:

const large_message[] = "Message1\000Message2\000Message3";
#define MESSAGE1 0
#define MESSAGE2 9
#define MESSAGE3 18

void mprint(int address) {
while (large_message[address] != '\000') {
putc(large_message[address++]);
}
}

Then you can call the function as:

mprint(MESSAGE1);

I use a very similar arrangement in my own code, with four seperate message tables, for different languages, then the 'mprint' routine, selects the right table according to the selected language, and the correct message is then printed from this.
As written the code will only work for short tables (remember the limits on the size of an integer), but it is fairly easy to extend this is needed.

This saves space, because the compiler has to generate a table 'setup' routine, for each seperate constant string. This can be as long as the string, for short messages. By combining all the messages into larger strings, you reduce the number of such 'setup' overheads generated.

Best Wishes
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[Ted]

Thanks for the link. The program stores two chars in a 14bit
rom place.
Originally it is used for eeprom storage and with read_eeprom()
the rom contents is readed.

I´ve a 16F76 and want to store strings in (program)-rom.
Storing a 14bit constant is possible, but how to read?

Any idea?

Regards Ted
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Original Post ID: 144515035

[Steve H.]

That's about all I know, it's annoying for us all. Either hand code some packing scheme or use external EEPROM. Danged if you do or danged if you don't.

In the past I've searched the board for ideas then used them as the basis for some third scheme that just barely works for the situation I'm in. When all else fails I've moved up a chip in memory size....

Best of luck,

Steve H.
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[Neutone]

:=:=I searched "String Rom" for 300 days back.
:=:=
:=:=See the link...
:=
:=
:=Also, if the chip is one of the 18x family (where individual instruction memory locations can store two bytes), this code becomes unecessary, _but_ you can still save space quite massively by putting several messages into one table.
:=Something like:
:=
:=const large_message[] = "Message1\000Message2\000Message3";
:=#define MESSAGE1 0
:=#define MESSAGE2 9
:=#define MESSAGE3 18
:=
:=void mprint(int address) {
:= while (large_message[address] != '\000') {
:= putc(large_message[address++]);
:= }
:=}
:=
:=Then you can call the function as:
:=
:=mprint(MESSAGE1);
:=
:=I use a very similar arrangement in my own code, with four seperate message tables, for different languages, then the 'mprint' routine, selects the right table according to the selected language, and the correct message is then printed from this.
:=As written the code will only work for short tables (remember the limits on the size of an integer), but it is fairly easy to extend this is needed.
:=
:=This saves space, because the compiler has to generate a table 'setup' routine, for each seperate constant string. This can be as long as the string, for short messages. By combining all the messages into larger strings, you reduce the number of such 'setup' overheads generated.
:=
:=Best Wishes

Taking this one step further you can use an index for delimited messages within a constant string. This is only usefull if the constant string is longer than 256 bytes. You can buy a package of software and toutorials from Peter Anderson that includes an example of this for use with CCS

<a href="http://www.phanderson.com/" TARGET="_blank">http://www.phanderson.com/</a>
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