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uni_student
Joined: 01 Aug 2007
Posts: 38
Location: AUckland, NEW ZEALAND
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| Temperamental UART - Help !!!! |
 Posted: Tue Nov 25, 2008 1:13 am |
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Hi, I am using a PIC18F452 and trying to communicate with a GPS chipset using UART. About 1 out of 20 times when I switch the power to the GPS, the PIC receives the information and displays it on the LCD, otherwise only one character is shown and that's it. Could this be timing or a logic level issue or something else? Any help appreciated.
Note: Relevant code below, most of the LCD intitialising cut out, LCD tested and works fine.
| Code: |
#include <18f452.h>
#include <string.h>
#fuses HS,NOLVP,NOWDT
#use delay (clock=20000000)
#use rs232 (baud=4800, xmit=PIN_C6, rcv=PIN_C7, parity=N, bits=8)
void LCD_INIT (int x);
void DATA_MANIP (unsigned int x);
void KEYPAD (void);
void GPS (void);
//
void main (){
int i, j;
char c[20], d[20];
DATA_MANIP (0x00); // ensure all bits are 0
delay_ms (1000);
output_high (GREEN_LED);
LCD_INIT (0); //Init lcd . Cursor top line
output_high (RS_LCD); //Data write
strcpy (c, "LCD DisplayLine1");
STRING (c);
delay_us(100);
if (kbhit()){
output_low (GREEN_LED);
GPS ();
}
}
void GPS (void){
char r;
while(TRUE){
r=getc();
DATA_MANIP (r);
}
}
void LCD_INIT (int x){
..............
}
void DATA_MANIP (unsigned int x){
output_high (EN_LCD);
output_bit ( D0_LCD, x & 0x01 );
output_bit ( D1_LCD, x & 0x02 );
output_bit ( D2_LCD, x & 0x04 );
output_bit ( D3_LCD, x & 0x08 );
output_bit ( D4_LCD, x & 0x10 );
output_bit ( D5_LCD, x & 0x20 );
output_bit ( D6_LCD, x & 0x40 );
output_bit ( D7_LCD, x & 0x80 );
output_low (EN_LCD);
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Nov 25, 2008 1:46 am |
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| Quote: | | when I switch the power to the GPS |
Does this mean the PIC is always on ? Only the GPS is being switched
off and then on again ?
| Quote: | | #use rs232 (baud=4800, xmit=PIN_C6, rcv=PIN_C7, ERRORS) |
At a minimum, you need to add the ERRORS parameter to the #use rs232
statement as shown. You have a big delay before you ever call getc().
If you get an overrun error, the ERRORS parameter will allow it to be
cleared automatically and prevent the UART from locking up. |
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uni_student
Joined: 01 Aug 2007
Posts: 38
Location: AUckland, NEW ZEALAND
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| Posted: Wed Nov 26, 2008 3:24 am |
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| Cheers. Works mint now!!! |
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