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Loop to read tables going infinite

 
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future



Joined: 14 May 2004
Posts: 330

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Loop to read tables going infinite
PostPosted: Sat May 22, 2004 10:48 pm     Reply with quote
I'm starting with C, seeing how things are...

I did this:

Code:
const char ter[256] = { 00, 01, 02, 03, 04, 05, 06, 07,10, 11, 12, 13, 14, 15, 16, 17,
                         10, 11, 12, 13, 14, 15, 16, 17,10, 11, 12, 13, 14, 15, 16, 17,
                        20, 21, 22, 23, 24, 25, 26, 27,10, 11, 12, 13, 14, 15, 16, 17,
                        30, 31, 32, 33, 34, 35, 36, 37,10, 11, 12, 13, 14, 15, 16, 17,
                        40, 41, 42, 43, 44, 45, 46, 47,10, 11, 12, 13, 14, 15, 16, 17,
                        50, 51, 52, 53, 54, 55, 56, 57,10, 11, 12, 13, 14, 15, 16, 17,
                        60, 61, 62, 63, 64, 65, 66, 67,10, 11, 12, 13, 14, 15, 16, 17,
                         10, 11, 12, 13, 14, 15, 16, 17,10, 11, 12, 13, 14, 15, 16, 17,
                        20, 21, 22, 23, 24, 25, 26, 27,10, 11, 12, 13, 14, 15, 16, 17,
                        30, 31, 32, 33, 34, 35, 36, 37,10, 11, 12, 13, 14, 15, 16, 17,
                        40, 41, 42, 43, 44, 45, 46, 47,10, 11, 12, 13, 14, 15, 16, 17,
                        50, 51, 52, 53, 54, 55, 56, 57,10, 11, 12, 13, 14, 15, 16, 17,
                        60, 61, 62, 63, 64, 65, 66, 67,10, 11, 12, 13, 14, 15, 16, 17,
                         10, 11, 12, 13, 14, 15, 16, 17,10, 11, 12, 13, 14, 15, 16, 17,
                        20, 21, 22, 23, 24, 25, 26, 27,10, 11, 12, 13, 14, 15, 16, 17,
                        30, 31, 32, 33, 34, 35, 36, 37,10, 11, 12, 13, 14, 15, 16, 17 };
   for(index=0; index<=255; index++) {
      delay_ms(1);
      putc(ter[index]);
   };


It goes to a infinite loop sending chars via serial port.

Compiler is 3.190.

Does anyone know what I am doing wrong?
Haplo



Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia

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PostPosted: Sat May 22, 2004 11:53 pm     Reply with quote
'index' is a byte variable (remember in CCS, int is one byte), so it will roll over to zero after 255. This means the condition index<=255 never becomes false, since index never becomes equal to 256 and always stays less or equal to 255.
future



Joined: 14 May 2004
Posts: 330

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PostPosted: Sun May 23, 2004 11:16 am     Reply with quote
I dont think I'll have to use a 16bit variable to do the indexing of a 256bytes array.

There has to be a way ;) even basic do that.
Humberto



Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata

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PostPosted: Sun May 23, 2004 11:27 am     Reply with quote
The program is doing what you coded:
Code:

 for(index = 0; index <= 255; index++)


Probably you want to do:
Code:

 for(index = 0; index < 255; index++)


HTH

Humberto
future



Joined: 14 May 2004
Posts: 330

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PostPosted: Sun May 23, 2004 12:00 pm     Reply with quote
But this way the last char of the table will not be sent.

That's why I used <= Rolling Eyes
Humberto



Joined: 08 Sep 2003
Posts: 1215
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PostPosted: Sun May 23, 2004 12:24 pm     Reply with quote
Your consult was regarding this matter:
Quote:

It goes to a infinite loop sending chars via serial port.


A byte variable size is 255 bits, NOT 256

Humberto
future



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Posts: 330

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PostPosted: Sun May 23, 2004 12:54 pm     Reply with quote
How do you do something like this?

Would you declare an int16 variable to do the indexing?
rwyoung



Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA

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PostPosted: Sun May 23, 2004 1:14 pm     Reply with quote
I'd do this and let the index roll over

Code:

index=0;
while(1)
{
   delay_ms(1);
   putc(ter[index++]);
}


Or, if you wanted to leave after the 255th

Code:

index=0;
do
{
   delay_ms(1);
   putc(ter[index++];
} while(index); // or index!=0 if you prefer

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Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!
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