Communicate with bq27621 & bq27441

Hi all,

I am facing a big problem in communicate with these chip by I2C protocol (I use F28335 I2C module) . Write or read  registers of these chip is really strange. Sometime got right results but sometime i got wrong result again and again. Such as: when i try reading a register many time (for example designed capacity) i get many different values (of course true value is one of them). Please help me if you know why.

Below is my program config I2C:

// Initial for I2C module
void init_I2C(void)
{

	EALLOW;
	/* Enable internal pull-up for the selected pins */
	// Pull-ups can be enabled or disabled disabled by the user.
	// Comment out other unwanted lines.

	GpioCtrlRegs.GPBPUD.bit.GPIO32 = 1; 	// Disable pull-up for GPIO32 (SDAA)
	GpioCtrlRegs.GPBPUD.bit.GPIO33 = 1; 	// Disnable pull-up for GPIO33 (SCLA)

	/* Set qualification for selected pins to asynch only */
	// This will select asynch (no qualification) for the selected pins.
	// Comment out other unwanted lines.

	GpioCtrlRegs.GPBQSEL1.bit.GPIO32 = 3;  	// Asynch input GPIO32 (SDAA)
	GpioCtrlRegs.GPBQSEL1.bit.GPIO33 = 3;  	// Asynch input GPIO33 (SCLA)

	/* Configure SCI pins using GPIO regs*/
	// This specifies which of the possible GPIO pins will be I2C functional pins.
	// Comment out other unwanted lines.

	GpioCtrlRegs.GPBMUX1.bit.GPIO32 = 1;   	// Configure GPIO32 for SDAA operation
	GpioCtrlRegs.GPBMUX1.bit.GPIO33 = 1;   	// Configure GPIO33 for SCLA operation

	EDIS;


	I2caRegs.I2CPSC.all = 14;   // Prescaler - need 7-12 Mhz on module clk (150/15 = 10MHz)


	I2caRegs.I2CCLKL = 12;			// NOTE: must be non zero			1.7us
	I2caRegs.I2CCLKH = 5;			// NOTE: must be non zero			1us  --> I2C frequency: 370KHz
	I2caRegs.I2CIER.all = 0x24;		// Enable SCD & ARDY interrupts


	I2caRegs.I2CMDR.all = 0x0020;	// Take I2C out of reset
									// Stop I2C when suspended

	I2caRegs.I2CFFTX.all = 0x6000;	// Enable FIFO mode and TXFIFO
	I2caRegs.I2CFFRX.all = 0x2040;	// Enable RXFIFO, clear RXFFINT



	// Interrupts that are used in this example are re-mapped to
	// ISR functions found within this file.
	EALLOW; // This is needed to write to EALLOW protected registers
	PieVectTable.I2CINT1A    = &i2c_rxa_isr;
	EDIS;   // This is needed to disable write to EALLOW protected registers


    //	PieCtrlRegs.PIECTRL.bit.ENPIE = 1;		// Use in init_Sci_B

	// Enable I2C interrupt 1  in the PIE: Group 8
	PieCtrlRegs.PIEIER8.bit.INTx1 = 1;

	// Enable CPU INT8 which is connected to PIE group 8
	IER |= M_INT8;

}


// write i2c function
void I2C_write_data(unsigned int slave_addr, unsigned int length)
{

	unsigned int jdex;


	while(I2caRegs.I2CMDR.bit.STP == 1);

	// Check if bus busy
	while(I2caRegs.I2CSTR.bit.BB == 1);




	// Setup slave address
	I2caRegs.I2CSAR = slave_addr;

	// Setup number of bytes to send
	// MsgBuffer + Address
	I2caRegs.I2CCNT = length;

	// Setup data to send
	for (jdex=0; jdex<length; jdex++)
	{
	  I2caRegs.I2CDXR = *(i2c_write_buff+jdex);
	}

	// Send start as master transmitter
	I2caRegs.I2CMDR.all = 0x6E20;
}



// I2C read function
void I2C_read_data(unsigned int slave_addr, unsigned int cmd_length)
{

	unsigned int jdex;


	// Wait until the STP bit is cleared from any previous master communication.
	// Clearing of this bit by the module is delayed until after the SCD bit is
	// set. If this bit is not checked prior to initiating a new message, the
	// I2C could get confused.
	while(I2caRegs.I2CMDR.bit.STP == 1);

	// Check if bus busy
	while(I2caRegs.I2CSTR.bit.BB == 1);



	I2caRegs.I2CSAR = slave_addr;

	I2caRegs.I2CCNT = cmd_length;

	// Setup data to send
	for (jdex=0; jdex<cmd_length; jdex++)
	{
		I2caRegs.I2CDXR = i2c_cmd[jdex];
	}

	I2caRegs.I2CMDR.all = 0x2620;			// Send cmd with no stop

	user_delay(10000);       --> delay 940us

	I2caRegs.I2CCNT = i2c_receive_length;			// Setup how many bytes to expect
	I2caRegs.I2CMDR.all = 0x2C20;					// Send restart as master receiver
}


// This code I read designed capacity

		i2c_write_buff[0] = 0x43;    // buffer i2c master write to slave
		I2C_write_data(0x55, 1);     // write
		user_delay(1000);   --> delay 94us > 66us

		i2c_cmd[0] = 0x43;         // adress master read from slave
		i2c_receive_length = 1;    // global variable: length of data I2c master will receive
		I2C_read_data(0x55, 1);   
		user_delay(1000);

                temp[0] = i2c_read_buff[0];    // data received from I2c will store in i2c_read_buff

		i2c_write_buff[0] = 0x43;    // 
		I2C_write_data(0x55, 1);
		user_delay(1000);   --> delay 94us > 66us

		i2c_cmd[0] = 0x44;
		i2c_receive_length = 1;    // global variable: length of data I2c master will receive
		I2C_read_data(0x55, 1);
		user_delay(1000);

                temp[1] = i2c_read_buff[0];

                // designed capacity = temp[1]+ temp[0]*256

This is the best code that i can communicate tto bqxx chip (got more right result).

Thanks for reading.

Best Regards.

Phien Nguyen