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rs232 problems Guest
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rs232 problems |
Posted: Wed Sep 29, 2004 12:17 pm |
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I wrote a small application to read from a GPS module and send whatever it reads to the PC.
Code: | #include <16f876.h>
#include <string.h>
#fuses XT, NOPROTECT, BROWNOUT, LVP, NOWDT, PUT
#use delay (clock=4000000)
#use rs232(baud=2400,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=GSM)
#use rs232(baud=4800,parity=N,xmit=PIN_C4,rcv=PIN_C5,bits=8,stream=HOSTPC)
#use rs232(baud=4800,parity=N,xmit=PIN_C2,rcv=PIN_C3,bits=8,stream=GPS)
.
.
fprintf(HOSTPC,"Ready");
.
.
while(1)
{
c = fgetc(GPS);
fputc(c,HOSTPC);
} |
When I run that program "Ready" is displayed correctly on my terminal. When the GPS unit starts to send the NMEA data I start to see garbage on my terminal except for the '$' and ',' characters. Both are displayed correctly and other characters are nothing but garbage.
I connected the GPS unit directly to my PC using max232 and it dumps the NMEA data correctly w/o any problem on my terminal.
One more thing to say, I am using interrupt handler to deal with the GSM stream.
Code: | #INT_RDA
rda()
{
int8 c;
c=fgetc(GSM);
if(c==10)
{
sbuf[scnt-1]=0;
scnt = 0;
sflag=1;
} else
{
sflag = 0;
sbuf[scnt++]=c;
}
} |
Any idea? |
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Humberto
Joined: 08 Sep 2003 Posts: 1215 Location: Buenos Aires, La Reina del Plata
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Posted: Wed Sep 29, 2004 12:46 pm |
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In your interrupt handler, I would try the following just to quit the interrupt handler as soon as posible.
Code: |
#INT_RDA
rda()
{
int8 c;
if(kbhit(GSM))
{
c=fgetc(GSM);
if(c==10)
{
sbuf[scnt-1]=0;
scnt = 0;
sflag=1;
}else
{
sflag = 0;
sbuf[scnt++]=c;
}
}
}
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best wishes,
Humberto |
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