Lookup Table

Gastón

Asim,

There are many ways to do it.  Some people use Matlab to generate the table, then save it as a CSV file and copy it into Excel or Notepad and edit it there.  Alternatively you can do the entire thing in Excel.

Lab 4 in the F28377D 1-day workshop uses a 5 quadrant look-up table generated this way, which I attach.  The workshop files are here:

http://processors.wiki.ti.com/index.php/F2837xD_Workshop

Hope this helps.

Regards,

Richard

/* sinetab.c */

// table section declaration
// #pragma DATA_SECTION(QuadratureTable,"QuadratureTableSection")

// quadrature look-up table: contains 5 quadrants of sinusoid data points
int QuadratureTable[40] = {
		0x0000,			// [0]  0
		0x18F8,	        // [1]  11.25
		0x30FB,	        // [2]  22.50
		0x471C,	        // [3]  33.75
		0x5A81,	        // [4]  45.00
		0x6A6C,	        // [5]  56.25
		0x7640,	        // [6]  67.50
		0x7D89,	        // [7]  78.75
		0x7FFF,	        // [8]  90.00
		0x7D89,	        // [9]  78.75
		0x7640,	        // [10] 67.50
		0x6A6C,	        // [11] 56.25
		0x5A81,	        // [12] 45.00
		0x471C,	        // [13] 33.75
		0x30FB,	        // [14] 22.50
		0x18F8,	        // [15] 11.25
		0x0000,	        // [16] 0
		0xE708,	        // [17] -11.25
		0xCF05,	        // [18] -22.50
		0xB8E4,	        // [19] -33.75
		0xA57F,        	// [20] -45.00
		0x9594,	        // [21] -56.25
		0x89C0,	        // [22] -67.50
		0x8277,	        // [23] -78.75
		0x8000,        	// [24] -90.00
		0x8277,	        // [25] -78.75
		0x89C0,	        // [26] -67.50
		0x9594,	        // [27] -56.25
		0xA57F,	        // [28] -45.00
		0xB8E4,         // [29] -33.75
		0xCF05,	        // [30] -22.50
		0xE708,	        // [31] -11.25
		0x0000,			// [32] 0
		0x18F8,	        // [33] 11.25
		0x30FB,	        // [34] 22.50
		0x471C,	        // [35] 33.75
		0x5A81,	        // [36] 45.00
		0x6A6C,	        // [37] 56.25
		0x7640,	        // [38] 67.50
		0x7D89 	        // [39] 78.75
		};

/* end of file */

Hii Gaston and Richard,

Board: TMS320F2808

Case:-1

In EPWMxA peripheral, is possible to compare a single time constant value at which

switching event occur using the register (CMPA).

{

int a=1000;

EPwm1Regs.TBPRD = 1900;

EPwm1Regs.TBPHS.half.TBPHS = 0;

EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;

EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1;

EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;

EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE;

EPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;

EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;  

EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;

EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;

EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO;

EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;

EPwm1Regs.AQCTLA.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR;

EPwm1Regs.AQCTLB.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLB.bit.CBU = AQ_CLEAR;

EPwm1Regs.CMPA.half.CMPA = a;

}

Case:-2

But in case of multiple time constant value i.e. sine lookup table, at EPWMxA peripheral how

to compare with the register (CMPA).

{

int a[22] = {50,65,78,89,97,100,99,93,84,72,57,43,28,16,7,1,0,3,11,22,35,50}

EPwm1Regs.TBPRD = 1900;

EPwm1Regs.TBPHS.half.TBPHS = 0;

EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;

EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1;

EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;

EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE;

EPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;

EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;

EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;

EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;

EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO;

EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;

EPwm1Regs.AQCTLA.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR;

EPwm1Regs.AQCTLB.bit.ZRO = AQ_SET;

EPwm1Regs.AQCTLB.bit.CBU = AQ_CLEAR;

EPwm1Regs.CMPA.half.CMPA = a[22];

}

# Any one please suggest me, how to assigning multiple time constant value in a Counter-Compare Register [CMPA / CMPB] and so it is continuously compared with the Time-Base-Counter Register [TBCTR] value and generate an appropriate event.

# Assigning Single time value and Multiple time value in Counter-Compare Register [CMPA / CMPB] may be different, because i am getting appropriate event in Single time value but not possible in multiple time value.
I have mentioned on the above comment for Case 1 i.e. single time value and Case 2 i.e. Multiple time value using sine lookup table.

Hi Asim,

I'm not completely sure I've understood your question.  The compare registers (CMBA & CMPB) are continuously compared with the TB counter and generate whichever event is assigned to them when there is a match.  To use the look-up table, you would typically generate an interrupt once per time-base period (say, on a zero match) and update the appropriate CMPx registers using the next value in the look-up table.  In this way the duty cycle is modulated according to sequential values in the look-up table.

If iths isn't what you meant, could you clarify what you mean by "single time" and "multiple time" please?  Thanks.

Regards,

Richard

Hii Richard,

--------------------------------------------------------------what you mean by "single time" and "multiple time" please? -----------------------------------------------------

Oct 31 Reply

Case:-1 Single time value Counter-Compare i.e

int a=1000;

EPwm1Regs.CMPA.half.CMPA = a;

Case:-2 Multiple time value Counter-Compare i.e.

int a[22] = {50,65,78,89,97,100,99,93,84,72,57,43,28,16,7,1,0,3,11,22,35,50};

EPwm1Regs.CMPA.half.CMPA = a[22];

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I am facing problem in Case:-2 that when i assigning lookup table i.e. a[22] in CMPA register i.e. EPwm1Regs.CMPA.half.CMPA = a[22]; and "debugging" and "Go Main", the Oscilloscope gives no output event. (Why??)

But in Case:-1 when i assigning,  int a=1000; EPwm1Regs.CMPA.half.CMPA = a;   and "debugging" and "Go Main", the Oscilloscope gives an appropriate event, i.e. Square wave pulse.