HELP with GPS

warriorfenix · Joined: 29 Dec 2009 Posts: 8 Location: España

Hola estoy realizando un programa que interprete las cadenas de caracteres que envia el GPS, lo simulo con proteus y funciona correctamente, pero cuando lo quemo en el pic, no muestra nada en la lcd. Por favor revisen mi codigo fuente, y diganme que es lo que esta mal. gracias

Rohit de Sa · Joined: 09 Nov 2007 Posts: 282 Location: India

English, please. http://translate.google.com

I looked at the fuses, saw "WDT"; then I looked through your code for a "restart_wdt"; didn't find it; and then stopped looking any further. Fix this first.

Rohit

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Always add the 'ERRORS' keyword to the #rs232 line to prevent the UART from blocking.

warriorfenix · Joined: 29 Dec 2009 Posts: 8 Location: España

I tried to set the WDT in various parts of the program

guest1 · Guest

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Start with an easy small program and when this works add more functions.

Do not use the watchdog in the prototype. Only add the watchdog when your program is working.

Do not use RDA interrupts. Your program does not need it and makes things difficult.

Guest · Posted: Wed Dec 30, 2009 7:54 am

I have removed the comparison of RXDATA IF, and I still get nothing. I do not understand how can he be ...

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

GPS modules usually transmit at 4800 baud. Use getc() instead of gets(). gets() looks for a 'string' of characters and int_rda is entered on every character. You are trying to send the word 'HOLA' everytime int_rda is entered. This will make your interrupt not work. You will lose incoming characters. If you want to send something to verify that you received data from the GPS then just send the same character that was just received with a putc(). You might want your #use rs232() to read:

warriorfenix · Joined: 29 Dec 2009 Posts: 8 Location: España

I made a simple program to send and receive with the serial port and the lcd, and it works, I added a putc (rxData) in the code, and forwards all data correctamnte. But I'm not on the LCD displays the data. What could go wrong?

mccoyb · Joined: 02 Jan 2010 Posts: 1

I have some code I wrote for parsing two GPS NMEA strings:
$GPGGA and $GPRMC (if I'm remembering those correctly). I don't have it in front of me but I can post it tonight when I have it available. Let me know if you want that code.

I'm currently using the code to parse NMEA strings from 2 GPS units: a Garmin eTrex and a USGlobal Sat EM-406A SiRF III Receiver ( http://www.sparkfun.com/commerce/product_info.php?products_id=465 ).

My code works well with both, but be warned of very slight differences in NMEA strings, even though NMEA is a standard and they should be identical.

The parsing is a little more elaborate than what you have, so the code is slightly bigger, but hopefully it will work for you. I've run it in overnight tests and performed data logging and I haven't observed any memory over-runs or anything like that and it handles the empty NMEA strings if the GPS looses lock.

I believe I have one version of code that simply parses strings and one version that does the conversions to numbers. I recommend keeping it in string format and doing the conversion outside the function.

I'm running it on a PIC18F4620. Both GPS units run 4800 bps, on the standard 8 data bits, no parity, 1 stop bit (8-N-1).

Be careful about knowing your voltage levels from your GPS: TTL 0-5V? TTL 0-3V? RS-232 +7V/-7V? or whatever. Make sure you know whether your signal is getting inverted if you're doing conversion from RS-232 levels to TTL levels.
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Rochester, MN

el_tigre · Joined: 23 Dec 2007 Posts: 12 Location: Bs As : Argentina

Hola warriorfenix, hablo español ya que soy de Argentina. Me parece que te cuesta entender algunas cosas de las que te estan planteando.
En primer lugar te recomiendo no usar interrupciones para recibir los caracteres de la cadena del GPS, por que tarde o temprano vas a tener problemas... dado que las cadenas que envian son bastante grandes y con una frecuencia importante, al menos veo eso en el modelo con el que estoy trabajando.

una sujerencia de un loop que sin usar interrup te levanta caracter y lo manda...ademas en tu post anterior estas usando mal la rutina en la interrupcion... proba esto....

void main() {
disable_interrupts(global);
cd_init();

while(true){ // loop eterno....
while(!kbhit()){restart_wdt();} // espera que llegue dato, mientras resetea el watchdog, cuando pasa esta linea es por que ha data
rxData=getc(); // aca levantas el dato
mando_lcd(rxData); // esto no va a andar por que no esta definido pero si pones la funcion que uses para mandar data al lcd te lo deberia mostraar
} // vuelve al looptendrias que postear el codigo entero para poder ayudarte mejor
en tu post anterior cuando pones

rxData=getc();
putc(rxData);
if (comaCount == 0) {

lo que va a hacer es mandar por 232 el caracter que recibio...para que putc() mande al lcd le tenes que decir que escriba en el lcd, la funcion putc por default lo manda al stream que quedo, pero para manejar flujos por diferentes lados tenes que usar fputc(stream, dato) entonces si definis que el stream del LCD es lcd_stream, para mandar por ahi deberia quedar asi:

fputc(lcd_stream,rxData);

POnete el codigo entero que estas usando, cuando arranca el main implemnta un linea que escriba algo en el lcd, asegurate que funciona (que realmente lo escribe) y te puedo ayudar a hacerlo andar.
Saludos

el_tigre · Joined: 23 Dec 2007 Posts: 12 Location: Bs As : Argentina

Me olvide de contarte que encontre tu post por que casualmente estoy trabajando en un sistema similar... en mi caso tengo una placa GolbalSat modelo ET-102, pero por lo que veo casi todas manejan el mismo protocolo...bueno, cuando postees seguimos, saludos.

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El Tigre,

Éste es un foro internacional que se conduce en inglés.
Siga por favor esta regla.

-- Forum Moderator
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Sebastian Cohn
www.bit03.com.ar
Desarrollos Electronicos

warriorfenix · Joined: 29 Dec 2009 Posts: 8 Location: España

I've managed to get good chains, was no problem either global variables initialized at the beginning of the program. The problem I have now is that I can not show good values in the lcd, the text displayed does not last long enough in the lcd.

el_tigre · Joined: 23 Dec 2007 Posts: 12 Location: Bs As : Argentina

SPA: No me queda claro algo, no entran en el LCD o el tiempo de actualizacion es tan breve que no llegas a ver los valores?.

ENG: I do not understand something, do not enter the LCD or update time is so short as to not get to see the values?
_________________
Sebastian Cohn
www.bit03.com.ar
Desarrollos Electronicos

warriorfenix · Joined: 29 Dec 2009 Posts: 8 Location: España

El problema es qu antes el programa no funcionaba bien, por que no tenia las variables globales inicializadas a cero. una vez inicializadas, no tengo problema en la recepcion de caracteres. El problema que tengo ahora es que no puedo mostrar en la lcd, los valores de las variables que recibo durante el tiempo que quiera, tres segundos, cinco, etc... se muestran las variables cuando reciben la orden durante un segundo y se sale. Laughing

Eng:
The problem is that before, the program was not working properly
because it did not have global variables initialized to zero. Once it is
initialized, it will have no problems in the reception of characters. The
problem I have now is I can not show on the lcd, the values of the
variables during the time I get like, three seconds, five, etc... it shows
the variables when they receive the order for a second and exits.