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noisepic
Joined: 24 Jul 2005
Posts: 20
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| display on LCD problem |
 Posted: Fri Aug 19, 2005 10:42 pm |
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I have some trouble when working with LCD
I want to display an unsigned char on LCD. For exam var=51;
when display it on LCD it always 50. Mean that it always display
(var-var%10).
and when I display float number, it take me a lot of memory. how to improve? |
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Ttelmah
Guest
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| Posted: Sat Aug 20, 2005 3:33 am |
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An integer should display fine. What you are not saying, is how you are getting 'to' this integer. If (for instance), this is being generated from earlier arithmetic, then the odds are that what you are seeing is a rounding error earlier on in the code.
If (for instance), you do:
| Code: |
float val;
int8 ival;
val=57500.0;
ival=val/1127.45;
printf("%u",ival);
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You may well find that 'ival', is actually 50, not 51. The problem here is that depending on how the numbers store, if the result ends up as (say) 50.9999, the default conversion will be a 'floor' conversion (taking the integer below). You can round for yourself, by adding 0.499999 to the result before converting to an integer, and there are some signs in the latest compiler, that CCS are working on this aspect of their compiler.
On the float, the libraries are 'not bad'. Floating point arithmetic, takes a _lot_ of work for a small processor like the PIC, and a lot of code size.
The best thing that can be done, is to see if your problem can instead be solved using 'fixed point' arithmetic in a scaled integer. Though the compiler has some bugs at the moment, CCS have just added support for this into the printf statement, with the %w format.
Best Wishes |
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noisepic
Joined: 24 Jul 2005
Posts: 20
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| Posted: Sun Aug 21, 2005 9:08 pm |
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I'm sorry this post is not clearly. Because of my english...
I want to display number such as 34.5,35,35.5..mean that each step is 0.5
If I use
[code]
printf(lcd_putchar,"%3.1f",val);
[\code]
it will take alot of memory. Or we have to buil a sub routine to display it.
I haven't tried %w format.
thanks |
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noisepic
Joined: 24 Jul 2005
Posts: 20
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| Posted: Sun Aug 21, 2005 9:26 pm |
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I'm sorry this post is not clearly. Because of my english...
I want to display number such as 34.5,35,35.5..mean that each step is 0.5
If I use
| Code: |
printf(lcd_putchar,"%3.1f",val);
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it will take alot of memory. Or we have to buil a sub routine to display it.
I haven't tried %w format.
thanks |
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Ttelmah
Guest
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| Posted: Mon Aug 22, 2005 2:18 am |
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%w, is the answer to what you want. Use a long int, and increment it by 5, then output it with %3.1w
The value will need to be a long, since for the example you give, you need to hold '345', '350' etc., which won't fit in an 8bit integer.
You can get the same effect in older compilers, using something like:
| Code: |
ldiv_t val;
int16 ival;
//declare these where required. You must include stdlib.h beforehand.
ival=345;
//any value you want.
val=ldiv(ival,10L);
printf("%2ld.%1ld",val.quot,val.rem);
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The printf here will output '34.5' for the 'ival' given.
Best Wishes |
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