I2C problems with the LPC-E2129 Development board

Development Boards MicroMod
1

Hello,

I’m trying to get the I2C bus working on the LPC-E2129 Development board. I program with CrossStudio. This is working great. I can debug with the JTAG interface very nice.

I think I initialize the I2C good. You can find the code I used at the end of this messaged.

If I look in the scheme of the development board, I see that there is a pull-up resistor on the SDA line. This is resistor R37, connected to the 3.3 Volt en the SDA line. There is no pull-up resistor on the SCL line. Why? In my measurement with a scope a can see that there is some activity on the SLC line and no activity on the SDA line. But this I can see only if I connected a 8K pull-up resistor to the SLC line. I don’t understand this. Can some one please help my.

Thanks

//main.cpp
#include <targets/LPC210x.h>
#include "I2C.h"

#define CAM_ADDRESS 0xA0

int main(void){
  I2C i2c;
  i2c.InitI2C();
  while(1){
    i2c.SendSlaveAdress(CAM_ADDRESS);
  }
   return 0;
}

//I2C.h
#define STA	0x20
#define SIC	0x08
#define SI	0x08
#define STO	0x10
#define STAC    0x20
#define AA	0x04

class I2C{
  private:
    
  public:
    I2C(void);
    void delay(int);
    void InitI2C(void);
    void SendSlaveAdress(int addressSlave);
    int ReadOnI2C(void);
    void WriteOnI2C(int data);
};

I2C::I2C(void){
  
}
void I2C::delay(int d){     
  for(; d; --d){
    asm volatile ("nop");
  }
}

void I2C::InitI2C(void){  
	//  Set pinouts as scl and sda
	PINSEL0  |= 0x00000050;
	PINSEL0  &= 0xFFFFFF5F;
	
	I2SCLL = 400;
	I2SCLH = 400;
        I2CONCLR = 0xFF;
	delay(10);

	I2CONSET = 0x00000040;  //Active Master Mode on I2C bus
}


void I2C::SendSlaveAdress(int addressSlave){	
	if(!(addressSlave & 0x01)){ //test if it's a master adress
		//while(I2C_I2STAT!=0xF8);	
		I2CONSET = STA;
		while(I2STAT != 0x08); 	//Set and wait the start		
		I2DAT = addressSlave; // Charge slave Address
		I2CONCLR = SIC | STAC; // Clear i2c interrupt bit to send the data    
		while(I2STAT != 0x18 && !(I2CONSET & SI));	//wait the ACK		
	} else {			//it's a slave adress
		I2CONSET = STA;
		I2CONCLR = SIC;
		while(I2STAT != 0x10 && !(I2CONSET & SI)); 	//Set and wait the start		
		I2DAT = addressSlave; // Charge slave Address	
		I2CONCLR = SIC | STAC; // Clear i2c interrupt bit to send the data    
		while(I2STAT != 0x40 && !(I2CONSET & SI));	//wait the ACK
	}
}


int ReadOnI2C(void){
	I2CONCLR = SIC;//ACK from the master
	while(I2STAT != 0x50 && !(I2CONSET&SI)); //wait the data 
        // Read the data...  
	return I2DAT;	
}

void WriteOnI2C(int data){
	I2DAT = data; // Charge Data 
	I2CONCLR = SIC; // Clear i2c interrupt bit to send the data    	
	while(I2STAT != 0x28 && !(I2CONSET & SI));	//wait the ACK
}
2

Most I2C setups have a pull-up on the data line (SDA) and not the clock line (SCL). This is because the master ALWAYS controls the clock, while the data line is controlled by the clock, and then released so that the slave can talk back to the master. When the data line goes floating, a pull-up resistor must be installed to work correctly.

Sorry - I can’t comment on your code. Maybe someone else will be able to wade through it. We do offer example PIC code if it helps : http://www.sparkfun.com/tutorial/coding/1-intro.htm

-Nathan