SPI with 28335

Jimit Doshi

Other Parts Discussed in Thread: TMS320F28335

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!

over 11 years ago

0 Jimit Doshi over 11 years ago

Prodigy 170 points

Hello All,

Just to add to my post above, those commented DELAY_US() routines do not make any difference to the code behavior and the Slave board still misses about one third of all the messages sent to it.

Thanks,

Jimit

0 Brett Larimore over 11 years ago in reply to Jimit Doshi

TI__Guru 57255 points

Jimit,

Below I've listed a few things I'd take a look at:

1) I'd would recommend taking a look at the signals between the two chips with an oscilloscope to try to see the issue visually. This will help you determine whether the issue is that the slave is not receiving the master's data or if the master is not receiving the data that the slave has sent back.

2) Also are there any interrupts in your system? If so, make sure that they don't eat up cycles when you don't want them to.

3) How far apart are the master and the slave?

4) If you try with a slower baud rates does the probability of successful transactions increase?

Thank you,
Brett

C2000™︎ microcontrollers

C2000 microcontrollers forum

SPI with 28335