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sheing3003
Joined: 05 Jul 2006
Posts: 10
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| problem with putc() |
 Posted: Sat Jul 22, 2006 9:00 pm |
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i need help with putc(), it's a strange problem,
i declare int8 dummy, dummy1;
| Code: |
dummy=1;
dummy1=255;
printf("start");
for(i=0;i<12928;i++)
if((i%129)==0)
putc(dummy);
else
putc(dummy1);
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and dummy1 and dummy are suppose to be color data (0 being white, and 255 being black)
when I use 1 as white everything works perfect, but when I set dummy=0, then the picture is all messed up
the pc software has no problem, I can use 0 when no communication with PIC...so can putc() not send 0?
Thanks in advance |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 22, 2006 11:20 pm |
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Yes, putc() can send a 0. Here is a test program:
| Code: |
#include <16F877.h>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//======================
void main()
{
int8 c;
c = 0;
putc(c);
while(1);
} |
Here is the code generated by vs. 3.249 of the compiler,
with comments:
| Code: |
0000 00311 ... int8 c;
0000 00312 ...
0000 00313 ... c = 0;
0016 01A1 00314 CLRF 21 // Set 'c' to 0x00
0000 00315 ...
0000 00316 ... putc(c);
0017 0821 00317 MOVF 21,W // Move 'c' into W reg.
0018 1E0C 00318 BTFSS 0C.4 // Wait until UART is ready
0019 2818 00319 GOTO 018
001A 0099 00320 MOVWF 19 // Put W into the TXREG
0000 00321 ...
0000 00322 ...
0000 00323 ... while(1);
001B 281B 00324 GOTO 01B
0000 00325 ... }
SYMBOL TABLE
LABEL VALUE
main.c 00000021
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This code shows that a variable can be set to 0 and transmitted
by the UART. |
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Ttelmah
Guest
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| Posted: Sun Jul 23, 2006 3:23 am |
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As PCM programmer says, putc, must definately can send a '0'. I'd be wondering about other possible problems. How is the connection made?. remember a '0' will be unique in having eight consecutive 'low' bits, and some connections (wireless for example, or something with a capacitive connection), can at times show problems with such a data pattern.
Best Wishes |
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sheing3003
Joined: 05 Jul 2006
Posts: 10
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| Posted: Tue Jul 25, 2006 12:17 pm |
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the connection is by serial port, rs232...
i don't know why it's behaving like that, it should work, but it's not...
the strangest thing is that when I replace 0 with 1, (there's 255 color bits so replacing 0 with 1 doesn't really matter, since our eyes cant tell), when i replace 0 with 1 everything works fine... but if i leave the 0 as it is my image get all screwed up....
still can't figure it out...
but i guess it works...probably just my program |
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Ttlemah
Guest
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| Posted: Tue Jul 25, 2006 2:50 pm |
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As a suggestion, are you using the 'MScomm' active-X control to retrieve the data at the PC?. If so, 'null discard', needs to be set to false, or 0 characters will not be returned...
Best Wishes |
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sheing3003
Joined: 05 Jul 2006
Posts: 10
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| Posted: Wed Jul 26, 2006 5:35 pm |
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| Ttlemah wrote: | As a suggestion, are you using the 'MScomm' active-X control to retrieve the data at the PC?. If so, 'null discard', needs to be set to false, or 0 characters will not be returned...
Best Wishes |
ooo!! that might be the reason! thanks for the suggestion
now i gotta figure out how to set that to false...lol |
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