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RS485 - problem with pointer

 
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emil86



Joined: 14 Nov 2006
Posts: 6
Location: Austria, Vienna

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RS485 - problem with pointer
PostPosted: Fri Jan 05, 2007 8:20 am     Reply with quote
hy guys,

first i want to thank you for thisgreat forum you helped me a much till now.

please take a look at my source code and tell me if the type definitons are ok, because this is my first time i have to do with pointers in C. Is the parameter in the function call ok ? and are there any errors in the rs485.c from CCS ?? i have absolutly no idea, because sometimes it works, and sometimes it doesn't. Is it ok to let the RX_ENABLE pin the whole time low ?

thx in advance,
emil

Code:

#include <18f2580.h>
#fuses INTRC_IO, NOWDT, NOMCLR, NOLVP, NOPROTECT
#use delay(clock=8000000)
#define RS485_ID  1                 // The device's RS485 address or ID
#define RS485_USE_EXT_INT FALSE        // Select between external interrupt
#define RS485_RX_PIN       PIN_C7   // Data receive pin
#define RS485_TX_PIN       PIN_C6   // Data transmit pin
#define RS485_ENABLE_PIN   PIN_C5   // Controls DE pin.  RX low, TX high. Pin 1 von unten
#include <rs485.c>
#include <lcd_HD44780_4x16.c>

typedef struct
{
int8 from_id;    //
int8 length;    //
int8 data;      //
}receive_buffer;

typedef struct
{
int8 to_id;    //
int8 length;    //
int8 data;      //
}send_buffer;
/** H A U P T P R O G R A M M *************************************************/

void main(void)
{
   receive_buffer rb;
   send_buffer sb;
   char text[15];
   setup_oscillator(OSC_8MHZ|OSC_INTRC|OSC_PLL_OFF);   //stellt die Frequ. auf 8MHz
   lcd_init();            //initialisiert das LCD
   rs485_init();
   lcd_clearlcd();
   lcd_gotoxy(1,1);
   printf(lcd_putc,"MASTER ID1 init.");
   delay_ms(500);

   sb.to_id=2;
   sb.length=8;
   sb.data=1;                    //Initialisiert den Slave
   rs485_send_message(sb.to_id,sb.length,&sb.data); //Paket an Slave mit ID2 und Data1
   delay_ms(400);
   rs485_get_message(&rb,TRUE);  //Warte auf Antwort
   lcd_gotoxy(1,2);
   sprintf(text,"ID%i erreichbar",rb.from_id);
   printf(lcd_putc,text);

/*   sb.to_id=3;
   sb.length=8;
   sb.data=1;                    //Initialisiert den Slave
   rs485_send_message(sb.to_id,sb.length,&sb.data); //Paket an Slave mit ID3 und Data1
   rs485_get_message(&rb,TRUE);  //Warte auf Antwort
   lcd_gotoxy(1,3);
   sprintf(text,"ID%i erreichbar",rb.from_id);
   printf(lcd_putc,text);
*/

   while (TRUE)
   {
   sb.to_id=2;
   sb.length=8;
   sb.data=1;                    //Fortlaufendes Pakete senden
   rs485_send_message(sb.to_id,sb.length,&sb.data); //Paket an Slave mit ID2 und Data1
   delay_ms(50);
   rs485_get_message(&rb,TRUE);  //Warte auf Antwort
   lcd_gotoxy(1,2);
   sprintf(text,"I:%i B:%i D:%i",rb.from_id,rb.length,rb.data);
   printf(lcd_putc,text);

/*   sb.to_id=3;
   sb.length=8;
   sb.data=1;                    //Fortlaufendes Pakete senden
   rs485_send_message(sb.to_id,sb.length,&sb.data); //Paket an Slave mit ID3 und Data1
   rs485_get_message(&rb,TRUE);  //Warte auf Antwort
   lcd_gotoxy(1,2);
   sprintf(text,"I:%i B:%i D:%i",rb.from_id,rb.length,rb.data);
   printf(lcd_putc,text);
*/
   }

}
Ttelmah
Guest
PostPosted: Fri Jan 05, 2007 8:43 am     Reply with quote
You have 'data' in each structure defined as a single int8 character. Then you start to use it as if it was an array of characters. The only array you have present, is the 'text' array. You need an array inside the buffers....

Best Wishes
emil86



Joined: 14 Nov 2006
Posts: 6
Location: Austria, Vienna

View user's profile Send private message ICQ Number

PostPosted: Fri Jan 05, 2007 10:43 am     Reply with quote
....
emil86



Joined: 14 Nov 2006
Posts: 6
Location: Austria, Vienna

View user's profile Send private message ICQ Number

PostPosted: Sat Jan 06, 2007 11:54 am     Reply with quote
Sorry i can't find the line where i am using the 'data' variable like an array.

And how should i fix my source code so it will be okay?

Thanks in advance.
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Sat Jan 06, 2007 12:41 pm     Reply with quote
Code:

 sb.length=8;
 sb.data=1;                    //Initialisiert den Slave
 rs485_send_message(sb.to_id,sb.length,&sb.data); //Paket an Slave mit ID2 und Data1


Length is in bytes not bits. You data is only 1 byte long but you tell it to send 8 bytes.
emil86



Joined: 14 Nov 2006
Posts: 6
Location: Austria, Vienna

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PostPosted: Sat Jan 06, 2007 12:46 pm     Reply with quote
GE thanks a lot

You guys saved me again!!
Ttelmah
Guest
PostPosted: Sat Jan 06, 2007 1:45 pm     Reply with quote
emil86 wrote:
Sorry i can't find the line where i am using the 'data' variable like an array.

And how should i fix my source code so it will be okay?

Thanks in advance.

In the 'send message' call, you have a length, and the address of data. What happens if the length is more than one...

Best Wishes
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