I2C in PIC18F4520

Dear all,

I am trying to use I2C module in PIC 18F4520 but I got some troubles. I can not produce a 100kHz pulse on SCL pin of the PIC. I use MPLAB C18 and its standard library to program.
This is the function from i2c.h: OpenI2C(MASTER,SLEW_OFF); (Config I2C Mode Master, Clock 100Khz). However, when I use osciloscope to measure the frequency of the pulse on SCL, it generates a nearly 500kHz on this pin.
Can anyone help me? Thanks

hmk

You could write to SSPADD after you call OpenI2C. Personally, I wrote my own routines, I can post them if it would help.

Mike.

Hi Mike,

Thank you for your help but I have tried that way and it still did not work. When I demo the circuit by Proteus, it only runs in write process but can not receive data from ds1307. Here is a part of my code for this, can you read and comment?

void nhanACK()
{
while(SSPCON2bits.ACKSTAT);
SSPCON2bits.ACKSTAT = 1;
}
void write_i2c_all(void)
{
StartI2C(); // Start I2C
WriteI2C(0xD0); // Write mode
nhanACK();
WriteI2C(0x00); // address 0x00
nhanACK();
WriteI2C(second1&0x7f); // Write second
nhanACK();
WriteI2C(minute1); // Write minute
nhanACK();
WriteI2C(hour1); // Write hour
nhanACK();
WriteI2C(day1); // Write day
nhanACK();
WriteI2C(date1); // Write date
nhanACK();
WriteI2C(month1); // Write month
nhanACK();
WriteI2C(year1); // Write year
nhanACK();
WriteI2C(0x90);
nhanACK();
StopI2C();
}

void read_i2c_all(void)
{
StartI2C(); // Start I2C
WriteI2C(0xD0); // Write mode
nhanACK();
WriteI2C(0x00); // address 0x00
nhanACK();

RestartI2C(); // Start I2C
WriteI2C(0xD1); // Read mode
nhanACK();
second = ReadI2C(); // Read second
AckI2C(); // ACK
minute = ReadI2C(); // Read minute
AckI2C(); // ACK
hour = ReadI2C(); // Read hour
AckI2C(); // ACK
day = ReadI2C(); // Read day
AckI2C(); // ACK
date = ReadI2C(); // Read date
AckI2C(); // ACK
month = ReadI2C(); // Read month
AckI2C(); // ACK
year = ReadI2C(); // Read year
NotAckI2C(); // Not ACK
Delay10TCYx(1);
StopI2C(); // Stop I2C

}
void main (void)
{
int k;
TRISD=0x00;//so thu 1
OpenI2C(MASTER,SLEW_OFF); // Config I2C Mode Master, Clock 100Khz
SSPADD = 9;
second1 = 0x00; minute1 = 0x00;
hour1 = 0x00; day1 = 0x05;
date1 = 0x08; month1 = 0x08;
year1 = 0x08;

write_i2c_all();
Delay10TCYx(50);
while(1)
{
read_i2c_all();
delay_us(10);
PORTD=ma_bcd[second];
delay10ms();
}

}

Pommie said:

You could write to SSPADD after you call OpenI2C. Personally, I wrote my own routines, I can post them if it would help.

Mike.

Click to expand...

hi Pommie
i have problem with i2c functions in mplab c18 and connecting pic18F452 to
a serial eeprom such as 24C16 have you any example code.
thanks.