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i2c problem

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hadeelqasaimeh

Joined: 05 Jan 2006
Posts: 105

i2c problem

Posted: Wed Sep 27, 2006 2:15 am

hi all
I write a simple code to communicate between two pics. It don't work. I don't know why:

Master code:

Code:

#include <16f877a.h>
#include "lcd_kbd1.c"
#fuses XT,NOWDT,NOLVP
#use delay(clock=4000000)
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use I2C(master, sda=PIN_B0, scl=PIN_B1)
#byte tris_b =0xff
#byte tris_d =0xff

int8 value;

void main()
{ LCD_Init ( );

while(1)
{

value = input_d();

LCD_PutCmd ( CLEAR_DISP );
LCD_SetPosition ( 0x80);//80-8f
printf(LCD_PutChar,"value:");
LCD_SetPosition ( 0x88);//c0-cf
printf(LCD_PutChar,"%u",value);
delay_ms(1000);

i2c_start(); // Start condition
i2c_write(0xa0); // Device address/Read
i2c_write(value);
i2c_stop(); // Stop condition

}
}

and slave code

Code:

#include <16f877a.h>
#include "lcd_kbd1.c"
//#include <string.h>
#fuses XT,NOWDT,NOLVP
#use delay(clock=4000000)
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use I2C(slave,sda=PIN_C4,scl=PIN_C3,address=0xa0,FORCE_HW)
#byte tris_b =0x00 //rb0-rb3 are o/p
#byte tris_c =0x80

int8 value;

#INT_SSP //SPI or I2C activity

void ssp_isr()
{

if (i2c_poll())
{
value=i2c_read();
// LCD_PutCmd ( CLEAR_DISP );
// LCD_SetPosition ( 0x80);//80-8f
// / printf(LCD_PutChar,"value:");
// LCD_SetPosition ( 0x88);//c0-cf
// printf(LCD_PutChar,"%u",value);
output_high (PIN_B1);
delay_ms(500);
output_low (PIN_B1);

}
}

void main()
{

LCD_Init ( );
enable_interrupts(GLOBAL);
enable_interrupts(INT_SSP);

LCD_PutCmd ( CLEAR_DISP );
LCD_SetPosition ( 0x80);//80-8f
printf(LCD_PutChar,"welcome");

while(1)
{
output_high (PIN_B6);
delay_ms(1000);
output_low (PIN_B6);

}

}

I want just to send from master the value of port d, and receive them on slave then give indication or print on lcd Exclamation

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Wed Sep 27, 2006 1:15 pm

Quote:

I write a simple code to communicate between two pics,its dont work
,i dont know why.

Use the CCS example file for an i2c slave. It's called EX_SLAVE.C and
it's in this folder: c:\Program Files\Picc\Examples

Put the EX_SLAVE.C program in one PIC. Then put the program in
the following link on another PIC:
http://www.ccsinfo.com/forum/viewtopic.php?t=28097&start=9

Remember to add the pull-up resistors to the SCL and SDA signals.
(You can 2.2K or 4.7K resistors)

bsodmike

Joined: 05 Aug 2006
Posts: 52


Posted: Wed Sep 27, 2006 2:18 pm

An obvious question, why are you using hardware I2C on one, and software I2C on the other? Why not stick to hardware on both?

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Wed Sep 27, 2006 3:10 pm

Quote:

#use I2C(slave,sda=PIN_C4,scl=PIN_C3,address=0xa0,FORCE_HW)

In the i2c Slave statement above, the FORCE_HW is not needed.
The compiler will always generate code to use the PIC's hardware SSP
module. Note: This is only true for the slave.

Try it. Compile the EX_SLAVE.C example file, with and without
FORCE_HW. Then use the 'fc' command in a DOS window to compare
the two .LST files.

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