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brianm
Joined: 08 Mar 2008
Posts: 17
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| GPS (Lowrance) NEMA data to PIC16F690 c program |
 Posted: Sun Jul 26, 2009 6:40 pm |
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I have created the following code to read NEMA sentences. My problem is that I only get the first sentence and then the program is sitting waiting for more sentences....why is it not seeing the next sentence?
connecting the gps to to hyerterminal....all sentences are coming thru...
connected the PIC to hyperterminal and if I type in a sentence (anything) when I press enter it I see it returned to the terminal...exactly what I want. except of course I cant type as fast as the pic at 4800 baud.
Now I connect the GPS to the receive pin of the PIC and the transmit to hyperterminal using this code....
I get the first Nema sentence....so all wiring is correct but the C program is disregarding the next sentence(s).
What am I missing?
The PIC is connected to the GPS and the computer(hyperterminal) via the max232 RS232 driver/receiver chip.
Thanks all.
Brian
| Code: |
#include <16F690.h>
#fuses INTRC_IO, NOWDT, NOBROWNOUT, PUT, NOMCLR
#use delay(clock=4000000)
#use rs232(baud=4800, xmit=PIN_B7, rcv=PIN_B5)
#include <string.h>
//=============================
void main()
{
char input[80];
char word[6];
int x;
char c;
//strcpy(word, "124");
printf("Ready:\n\r ");
while(true)
{
printf("loop:\n\r ");
gets(input);
//strcpy(input, "$GPRMC,000856,A,5053.4290,N,10519.0989,W,3.5,138.0,010200,12.3,E*58");
puts(input);
}
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Jul 26, 2009 6:57 pm |
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You're sending a long string with the line above. While you're sending it,
the PIC can't do anything else. It takes about 2 ms per character (at
4800 baud) to send the string. So effectively, the PIC is locked up for
over 100 ms.
During that time, new characters may be coming into the UART's receiver.
But, it has only a 2-deep receive fifo. If more than 2 characters come in
without you reading them, the UART will generate an overrun error.
It will then stop receiving any future characters until that error condition
is cleared. You can tell the compiler to insert code to automatically
clear overrun errors by adding the ERRORS parameter to the #use rs232
statement. You'll still lose characters if you don't read them in time, but
at least the UART's receiver won't be locked up. |
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brianm
Joined: 08 Mar 2008
Posts: 17
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| ERRORS added to use rs232 line - losing data as stated.... |
| Posted: Sun Jul 26, 2009 7:36 pm |
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As stated in your suggestion I am losing data...makes perfect sense.
Now what can you suggest to make it so I don't lose data...I will be sending the data to a LCD once I get the proper data coming in...using the terminal program to test for now.
Thanks so much for the fast response and great explanation.
Brian |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Jul 26, 2009 8:05 pm |
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Use an interrupt-driven software receive fifo. Look at the Ex_Sisr.c
example file:
| Quote: | | c:\program files\picc\examples\ex_sisr.c |
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brianm
Joined: 08 Mar 2008
Posts: 17
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| was trying this example. |
| Posted: Sun Jul 26, 2009 8:41 pm |
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http://www.ccsinfo.com/forum/viewtopic.php?t=39659&highlight=rs232
I see this is similar to the example code you suggested. This examples is nice because $gprmc is the exact data I want to work with.
BUT with the original code I do get some mixed up data.
I replaced the lines as suggested and adjusted it for my PIC but get a compile error as shown.
| Code: |
xbuff =0;
do {
theChar = bgetc();
NMEA_RMC[xbuff++] = theChar;
} while (theChar != '*');
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The compile goes like this
Clean: Deleting intermediary and output files.
Clean Warning: File "D:\microchip\projects in c\rs232 inout using getc and buffer\rs232inoutgetc.o" doesn't exist.
Clean: Deleted file "rs232inoutgetc.ERR".
Clean: Done.
Executing: "C:\software\PICC\CCSC.EXE" +FM "rs232inoutgetc.c" +DF +LN +T +A +M +Z +Y=9 +EA
>>> Warning 207 "rs232inoutgetc.c" Line 69(1,1): Code has no effect
>>> Warning 207 "rs232inoutgetc.c" Line 99(1,1): Code has no effect
*** Error 75 "rs232inoutgetc.c" Line 108(1,2): Expect WHILE
*** Error 43 "rs232inoutgetc.c" Line 108(5,10): Expecting a declaration
*** Error 43 "rs232inoutgetc.c" Line 108(11,12): Expecting a declaration
*** Error 48 "rs232inoutgetc.c" Line 108(19,25): Expecting a (
*** Error 43 "rs232inoutgetc.c" Line 108(22,23): Expecting a declaration
*** Error 43 "rs232inoutgetc.c" Line 108(23,24): Expecting a declaration
*** Error 43 "rs232inoutgetc.c" Line 108(24,25): Expecting a declaration
*** Error 43 "rs232inoutgetc.c" Line 110(1,2): Expecting a declaration
8 Errors, 2 Warnings.
Halting build on first failure as requested.
BUILD FAILED: Sun Jul 26 20:30:17 2009
| Code: |
#include <16F690.h>
#fuses INTRC_IO, NOWDT, NOBROWNOUT, PUT, NOMCLR
#use delay(clock=4000000)
#use rs232(baud=4800, xmit=PIN_B7, rcv=PIN_B5, ERRORS)
#include <string.h>
char NMEA_RMC[58] ;
#include <STDLIB.H>
#include <MATH.H>
#define BUFFER_SIZE 58
int8 buffer[BUFFER_SIZE];
int8 next_in = 0;
int8 next_out = 0;
int xbuff=0x00;
char GPS_OK = 0;
#INT_RDA
void serial_isr() { // Serial Interrupt
int t;
buffer[next_in]=getc();
t=next_in;
next_in=(next_in+1) % BUFFER_SIZE;
if(next_in==next_out)
next_in=t; // Buffer full !!
}
#define bkbhit (next_in!=next_out)
int8 bgetc() {
BYTE c;
WHILE(!bkbhit) ;
c=buffer[next_out];
next_out=(next_out+1) % BUFFER_SIZE;
return(c);
}
void Ini_NMEA_RMC(void){ // Inicia a \0 cbuff -------------------
int i;
int count=58;
for(i=0;i<count;i++){ // Bucle que pone a 0 todos los
buffer[i]=0x00; // caracteres en el buffer
}
xbuff=0x00; // Inicializo el índice de siguiente
}
void main() {
int8 n = 0;
int32 i =0;
int8 theChar = 0;
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_spi(FALSE);
setup_wdt(WDT_OFF);
enable_interrupts(global);
enable_interrupts(int_rda);
delay_ms(50);
printf ("Ready \n\r");
do{
GPS_OK == 0;
WHILE (theChar != '$') theChar = bgetc(); // Look for a '$' - the start of a NMEA sentence
theChar = bgetc();
IF (theChar == 'G') {
theChar = bgetc();
IF (theChar == 'P') {
theChar = bgetc();
IF (theChar == 'R') {
theChar = bgetc();
IF (theChar == 'M') {
theChar = bgetc();
IF (theChar == 'C') {
theChar = bgetc(); // Discard ','
theChar = bgetc(); // Discard Time
WHILE (theChar != ',') theChar = bgetc();
xbuff =0;
//Ini_NMEA_RMC();
//while (theChar != '*'){
//NMEA_RMC[xbuff++] = bgetc();
do {
theChar = bgetc();
NMEA_RMC[xbuff++] = theChar;
}
while (theChar != '*');
printf ("%s \n\r", NMEA_RMC);
}
GPS_OK == 1;
}
}
}
}
}
} while (GPS_OK == 0);
}
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Sun Jul 26, 2009 9:01 pm |
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It appears you have too many closing braces just before the while statement at the end. Comment one out and it compiles.
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