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Problem with i2c_start() condition

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sv_shady

Joined: 07 Mar 2008
Posts: 28

Problem with i2c_start() condition

Posted: Sun Mar 16, 2008 2:49 am

I have a strange problem with the i2c bus. The pic is in master mode and should transmit data over the i2c, which is received from rs232. Here is the code:

Code:

#include <16F877A.h>
#device adc=8

#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES PUT //Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected

#use delay(clock=10000000)

#use i2c(Master, sda=PIN_C4, scl=PIN_C3, force_hw)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#define START_BYTE 0x41

int c;
int value_X;
int value_Y;

void INIT(void)
{
setup_adc(ADC_CLOCK_INTERNAL);
setup_adc_ports(NO_ANALOGS);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
}

void main()
{
INIT();
for(;;)
{
if(kbhit())
{
c = getc();
if(c == START_BYTE)
{
value_X = getc();
value_Y = getc();
i2c_start();
i2c_write(0x10);
i2c_write(value_X);
i2c_write(value_Y);
i2c_stop();
}
}
}
}

When i use the hardware i2c the PIC receives the data from rs232, but it stops at i2c_start() and i have to restart it. When i use software i2c this problem disapears... Any ideas why this happens ?
Thanks in advance Smile

P.S. The compiler is 4.057

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Sun Mar 16, 2008 8:43 am

Quote:

#use i2c(Master, sda=PIN_C4, scl=PIN_C3, force_hw)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#define START_BYTE 0x41

int c;
int value_X;
int value_Y;

void INIT(void)
{
setup_adc(ADC_CLOCK_INTERNAL);
setup_adc_ports(NO_ANALOGS);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED); // Delete this line
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
}

The setup_spi() statement re-configures the MSSP module.
It destroys the i2c mode setup that was done by the force_hw parameter.
To fix the problem, delete the line for setup_spi().

sv_shady

Joined: 07 Mar 2008
Posts: 28


Posted: Sun Mar 16, 2008 1:22 pm

Thanks a lot

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