BQ76920: I2C Connection not establishing with AVR ATTiny24A

Hi

Thanks for the Reply,

I am using 0x10 on the bus for the slave Address. Now, SDA is low and SCL is HIGH and is holding these states irrespective of Releasing of the Bus.

the pulse HIGH Time and Low Time I am using is as follows, as specified in D/S
#define I2C_TLOW 4.7
#define I2C_THIGH 4.0


unsigned char I2CAddress = 0x08; // device Address

/**All the Declaration of functions here*/
----------------
--------------
---------------

char readRegister(unsigned char address)
{
unsigned char i2c_Add = (I2CAddress << 1) | 0x01; // appending read bit at the LSB shifting the I2C Address 1 bit left
unsigned char readData;
device(I2CAddress);
I2c_write(address);
device(I2CAddress);
readData = I2C_read();
I2C_stp();
return readData;
}

void writeRegister(unsigned char address,unsigned char data)
{
unsigned char i2c_Add = I2CAddress << 1; // appending Write bit at the LSB shifting the I2C Address 1 bit left
I2C_start();
device(i2c_Add);
I2c_write(address);
I2c_write(data);
I2C_stp();
}



char USI_I2C_Master_Transfer(char USISR_temp)
{
USISR = USISR_temp; //Set USISR as requested by calling function

// Shift Data
do
{
USI_I2C_WAIT_LOW();
USI_CLOCK_STROBE(); //SCL Positive Edge
while (!(PIN_USI&(1<<PIN_USI_SCL))); //Wait for SCL to go high
USI_I2C_WAIT_HIGH();
USI_CLOCK_STROBE(); //SCL Negative Edge
} while (!(USISR&(1<<USIOIF))); //Do until transfer is complete

USI_I2C_WAIT_LOW();

return USIDR;
}


void I2C_start()
{
/////////////////////////////////////////////////////////////////
// Generate Start Condition //
/////////////////////////////////////////////////////////////////

USI_SET_SCL_HIGH(); //Setting input makes line pull high

while (!(PIN_USI & (1<<PIN_USI_SCL))); //Wait for SCL to go high

#ifdef I2C_FAST_MODE
USI_I2C_WAIT_HIGH();
#else
USI_I2C_WAIT_LOW();
#endif
USI_SET_SDA_OUTPUT();
USI_SET_SCL_OUTPUT();
USI_SET_SDA_LOW();
USI_I2C_WAIT_HIGH();
USI_SET_SCL_LOW();
USI_I2C_WAIT_LOW();
USI_SET_SDA_HIGH();

/////////////////////////////////////////////////////////////////
}

char device(unsigned char msg)
{
USI_SET_SCL_LOW();
USIDR = msg; //Load data

USI_I2C_Master_Transfer(USISR_TRANSFER_8_BIT);
USI_SET_SDA_INPUT();
if(USI_I2C_Master_Transfer(USISR_TRANSFER_1_BIT) & 0x01)
{
USI_SET_SCL_HIGH();
USI_SET_SDA_HIGH();
return 0;
}

USI_SET_SDA_OUTPUT();

}

char I2c_write(unsigned char *msg)
{
USI_SET_SCL_LOW();

USIDR = *msg; //Load data

USI_I2C_Master_Transfer(USISR_TRANSFER_8_BIT);

USI_SET_SDA_INPUT();

if(USI_I2C_Master_Transfer(USISR_TRANSFER_1_BIT) & 0x01) // NACK BIT
{
I2C_stp();
return 0;
}

USI_SET_SDA_OUTPUT();
return *msg;
}

char I2C_read()
{
unsigned char *msg;
USI_SET_SDA_INPUT();
*(msg)= USI_I2C_Master_Transfer(USISR_TRANSFER_8_BIT);
USI_SET_SDA_OUTPUT();

//if(msg_size == 1)
{
USIDR = 0xFF; //Load NACK to end transmission
}
//else
{
USIDR = 0x00; //Load ACK
}

USI_I2C_Master_Transfer(USISR_TRANSFER_1_BIT);

return *msg;
}

void I2C_stp()
{
/////////////////////////////////////////////////////////////////
// Send Stop Condition //
/////////////////////////////////////////////////////////////////

USI_SET_SDA_LOW(); // Pull SDA low.
USI_I2C_WAIT_HIGH();
USI_SET_SCL_HIGH();
while( !(PIN_USI & (1<<PIN_USI_SCL)) ); // Wait for SCL to go high.
USI_I2C_WAIT_HIGH();
USI_SET_SDA_HIGH(); // Release SDA.

while( !(PIN_USI & (1<<PIN_USI_SDA)) ); // Wait for SDA to go high.
USI_I2C_WAIT_LOW();

}

int main(void)
{

//master initialize
DDR_USI |= (1 << PORT_USI_SDA) | (1 << PORT_USI_SCL); // set PA4 (SCL) & PA6(SDA) as o/p pins
PORT_USI |= (1 << PORT_USI_SCL); // release SCL & SDA
PORT_USI |= (1 << PORT_USI_SDA);
USIDR = 0xFF;
USICR = (0 << USISIE) | (0 << USIOIE) | (1 << USIWM1) | (0 << USIWM0) | (1 << USICS1) | (0 << USICS0) | (1 << USICLK) | (0 << USITC);
USISR = (1 << USISIF) | (1 << USIOIF) | (1 << USIPF) | (1 << USIDC) | (0x00 << USICNT0); // Initializing I2C at Attiny

while (1)
{
writeRegister(0x00, 0xFF); // clearing SYS_STAT /// HERE I AM STUCK. SDA is LOW and SCL is Constant HIGH when at BUS I send 0x10. in case of 0x08 I get NACK.
/// rest of the code
}
}


Any suggestion ? what I am doing wrong ?

In Addition to above . I have verified the I2C Communication of Attiny24A with ADC3424. and verified the working of BQ76920 with Arduino Mega 2560. both are working individually. but there is a communication problem in between ATTiny24A and BQ76920.

Any thing which I have missed ??

Hi Bilal,
Unfortunately I'm not able to provide coding support. The AVR community may have good advice on setting up the peripherals, coding characteristics for the processor, or specific recommendations on I2C debug with that processor.
In general you may need to look at the bus to see who is driving it. If the bq76920 is holding the bus low it may have set the ACK and be holding it waiting for a clock, or may have started outputting data from a read. The standard bus-release mechanism in I2C is to send (up to 9?) clocks until the slave releases the bus. If the host is holding the SDA line it may be a peripheral setup issue.

Another suggestion here use ATTINY 84A instead of 24A there is a memory issue. One has to compromise some of the protection using 24A.