SPI with 28335

Hello All,

I am working on developing SPI communication between two TMS320F28335 devices, one acts as the master and the other as a slave.

I have set up message counters on both, the Master as well as the Slave module. I observe that the Slave consistently misses one third of the messages sent by the Master. This ratio remains pretty constant, irrespective of the actual number of messages (from a few hundreds to several thousands), indicating that it's a systematic problem .

Could some one take a look at the codes below and suggest where am I going wrong ?

28335 - Master :

// In main()

   SPI_Initialize();

   sdata = 0x0000;

   for(;;)
   {

	 sdata++;

	 //DELAY_US(1000);

	 SPI_Transmit(&sdata, 1);

	 //DELAY_US(1000);

	 SPI_Receive(&rdata, 1);


   }

//SPI Drivers for Master:

void SPI_Transmit (Uint16* tx_buff, Uint16 len)
{
	Uint16 byte_ctr = 0;
	volatile Uint16 dummy_rx = 0;

	ASSERT_CS();
	//DELAY_US(100);
	for (byte_ctr = 0; byte_ctr < len; byte_ctr ++)
	{
		SpiaRegs.SPITXBUF = *(tx_buff + byte_ctr);
		while (SpiaRegs.SPISTS.bit.INT_FLAG == 0)
		{}// Wait for transmission to complete!
		dummy_rx = SpiaRegs.SPIRXBUF;
	}
	//DELAY_US(100);
	RELEASE_CS();
	msg_ctr += len;

}

void SPI_Receive (Uint16* rx_buff, Uint16 len)
{
	Uint16 byte_ctr = 0;
	Uint16 dummy_tx = 0xFFFF;

	ASSERT_CS();
	//DELAY_US(100);
	for (byte_ctr = 0; byte_ctr < len; byte_ctr ++)
	{
		SpiaRegs.SPITXBUF = dummy_tx;
		while (SpiaRegs.SPISTS.bit.INT_FLAG == 0)
		{}// Wait for transmission to complete!
		*(rx_buff + byte_ctr) = SpiaRegs.SPIRXBUF;
	}
	//DELAY_US(100);
	RELEASE_CS();
	msg_ctr += len;
}

void SPI_Initialize()
{
	SpiaRegs.SPICCR.bit.SPISWRESET	=	0;  		// Reset SPI
	SpiaRegs.SPICCR.bit.SPICHAR 	=	(DATA_LEN - 1);
	SpiaRegs.SPICCR.bit.SPILBK		= 	0;
	SpiaRegs.SPICCR.bit.CLKPOLARITY	= 	0;

	SpiaRegs.SPIBRR					= 	BAUD_RATE;        // Baud rate = ((Crystal) * PLLCR / DIVSEL) / (2 * LOSPCP) / (SPIBRR + 1) = (30MHz * 10 /2 )/ (2*2) /(99 + 1) = 375kHz

	SpiaRegs.SPICTL.bit.CLK_PHASE	= 	0;
	SpiaRegs.SPICTL.bit.MASTER_SLAVE= 	1; 		//Master
	SpiaRegs.SPICTL.bit.OVERRUNINTENA = 0;		//Disable Overrun interrupt
	SpiaRegs.SPICTL.bit.TALK		=	1;
	SpiaRegs.SPICTL.bit.SPIINTENA	=	0;		//Disable interrupt

	SpiaRegs.SPICCR.bit.SPISWRESET	=	1;  		// Reset SPI

}

28335 - Slave:

//In Main

   SPI_Initialize_Slave();


   // Dummy operations, used only for debug
   for(;;)
   {
	   if (data_updt_flag == SET)
	   {
		   data_updt_flag = CLEAR;
		   rx_data = 0;

	   }
   }

// Slave SPI Init and ISR

void SPI_Initialize_Slave()
{
	SpiaRegs.SPICCR.bit.SPISWRESET	=	0;  		// Reset SPI
	SpiaRegs.SPICCR.bit.SPICHAR 	=	(DATA_LEN - 1);
	SpiaRegs.SPICCR.bit.SPILBK		= 	0;
	SpiaRegs.SPICCR.bit.CLKPOLARITY	= 	0;

	SpiaRegs.SPIBRR					= 	BAUD_RATE;        // Baud rate = ((Crystal) * PLLCR / DIVSEL) / (2 * LOSPCP) / (SPIBRR + 1) = (30MHz * 10 /2 )/ (2*2) /(99 + 1) = 375kHz

	SpiaRegs.SPICTL.bit.CLK_PHASE	= 	0;
	SpiaRegs.SPICTL.bit.MASTER_SLAVE= 	0; 		//Slave
	SpiaRegs.SPICTL.bit.OVERRUNINTENA = 0;		//Disable Overrun interrupt
	SpiaRegs.SPICTL.bit.TALK		=	1;
	SpiaRegs.SPICTL.bit.SPIINTENA	=	1;		//Enable interrupt

	SpiaRegs.SPICCR.bit.SPISWRESET	=	1;  	// Reset SPI

}

interrupt void spiRxTxIsr (void)
{
	rx_data = SpiaRegs.SPIRXBUF;
	SpiaRegs.SPITXBUF = 65535 - rx_data;

	data_updt_flag = SET;
	msg_ctr ++;

	SpiaRegs.SPIFFRX.bit.RXFFOVFCLR=1;  // Clear Overflow flag
	SpiaRegs.SPIFFRX.bit.RXFFINTCLR=1; 	// Clear Interrupt flag
	PieCtrlRegs.PIEACK.all|=0x20;       // Issue PIE ack
}

Also, I am controlling the chip select functionality of Master by using the corresponding pin as a GPIO (GPIO19) and not as SPISTEA/.

The character length is defined as 16 bits (DATA_LEN) and the baud rate is 375 kHz (verified).

Any help would be appreciated.

Thanks!