TWI / I2c device unable to read / write the device ? irrespective of following reference manual.

[Faizan]

Here are my functions which i wrote for reading / writing the i2c slave device ( after reading reference manual (nrf51422) . Unfortunately they are not working. Plz help me with the code.

void twi_init_slz(void )
{
	(*(unsigned volatile int *)0x040003500)= 0x00;               //Disable SPI AND TWI
	//(*(unsigned volatile int *)0x040003200)= 0x00; 							//SHORTCUT REGISTER
	(*(unsigned volatile int *)0x040003508)= 30U;								 //PSELSCL	
	(*(unsigned volatile int *)0x04000350C)= 7U;									//PSELSDA
	(*(unsigned volatile int *)0x050000518)= ~((1UL<<30)|(1UL<<7));
	(*(unsigned volatile int *)0x050000778)= (6UL<<8)|(3UL<<2);		//set pin
	(*(unsigned volatile int *)0x05000071C)= (6UL<<8)|(3UL<<2);		//set pin
	//(*(unsigned volatile int *)0x040003300)= (1UL<<2)|(1UL<<7)|(1UL<<7)|(1UL<<9)|(1UL<<14);	//INTEN
	(*(unsigned volatile int *)0x040003304)= (1UL<<2)|(1UL<<7)|(1UL<<7)|(1UL<<9)|(1UL<<14);	//INTENSET
	(*(unsigned volatile int *)0x040003524)= 0x01980000;				//FREQUENCY		
	(*(unsigned volatile int *)0x040003124)= 1UL;				//ERROR	

	(*(unsigned volatile int *)0x040003500)= 0x05;     //ENABLE TWI
}

void set_address_twi_slz(int address)
{
	(*(unsigned volatile int *)0x040003588)= address;				//I2C ADDRESS

}

int read_twi_slz(void)
{	
	nrf_delay_ms(10); 
	printf("In read\n");
	//(*(unsigned volatile int *)0x40003588)|= 1UL;	
	(*(unsigned volatile int *)0x40003000)= 1;						//STARTRX
	nrf_delay_ms(10); while(!((*(unsigned volatile int *)0x40003108))); //wait for RXREADY EVENT   
	nrf_delay_ms(10); 
	int read_i2c_value = (*(unsigned volatile int *)0x40003518); //copying RX Register
	nrf_delay_ms(10); 
	(*(unsigned volatile int *)0x40003014)= 1;		 //Stop
	return read_i2c_value;
}

bool write_twi_slz(int data)
{
	(*(unsigned volatile int *)0x40003008)=1;
	(*(unsigned volatile int *)0x4000351C)=data;
	int check =(*(unsigned volatile int *)0x04000351C);
	if(check)
	{
			return 1; // successfully sent
	}
	else
	{
			return 0; //Sent error
	}
}

[Stian Røed Hafskjold]

Why are you using the register addresses instead of the register names defined in nrf51.h? It makes your code really hard to read.

There is a TWI driver in the SDK that you can use instead of making all the low level functions your self. developer.nordicsemi.com/.../a00016.html

Also, can you please update your question with what is actually not working. If you are able to see any activity at all using a logic analyzer or oscilloscope, and your test setup in general. How do you know it doesn't work?

[Stian Røed Hafskjold]

The shifting is just a part of the TWI specification. TWI uses 7 bit addressing + a read/write bit: www.totalphase.com/.../200349176-7-bit-8-bit-and-10-bit-I2C-Slave-Addressing

So when using the TWI driver in the SDK you need to shift the address one bit left and add the R/W bit as LSB before passing the resulting uint8_t variable to the TWI functions.

If you write to the ADDRESS register directly, you can see in the data sheet that it consists of 7 bits, so no shifting is necessary.

You do not need any external pull ups for the SCL and SDA. When the PSELSCL and PSELSDA registers are set the pins are configured correctly.