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TI F281x PWM Configuration

Emmanuel ● April 18, 2011 ● Coded in C for the TI F28x

This piece of code contains a function which configures the basic features of the PWM module in TI F281x family. In this case it generates a period of 200 Hz with 60% duty cycle in PWM1 output. It is very simple to modify these parameters just by changing the value in CMPR1 AND T1PR registers.

/**********************************************************************/
#include "DSP281x_Device.h"
/***********************************************************************/

void InitPwm(void)
{

asm( "EALLOW");	//Enable write operations in protected registers

/*** Independent Compare Output Enable	*/

	EvaRegs.EXTCONA.bit.INDCOE= 1;

/********************************************************************
*	Write values in the two following registers until all the other
*	registers have been written, as their value depends on the other
*	registers. 							*
********************************************************************/

/*** Timer 1 Period Regiser	*/

	EvaRegs.T1PR = 0xB71A;			//use this value for a frequency of 200 Hz assuming
								    //sysclkout=150 MHz and its pre-scaler=16
								    
/*** CMPR1 Register Configuration */

	EvaRegs.CMPR1= 0x493D;		//to get 60% of duty cycle this value equals the 1-0.6= 40% period
		
/********************************************************************/

	EvaRegs.GPTCONA.all= 0x0050;
	
// bit 15 		0		Reserved 
// bit 14 		0		T2STAT GP timer 2 Status. 
// bit 13 		0		T1STAT GP timer 1 Status. 
// bit 12 		0		T2CTRIPE T2CTRIP Enable. 
// bit 11 		0		T1CTRIPE T1CTRIP Enable. 
// bit 10-9 	00		T2TOADC Start ADC with timer 2 event
// bit 8-7 		00		T1TOADC Start ADC with timer 1 event
// bit 6 		1		TCMPOE Timer compare output enable. 
// bit 5		0		T2CMPOE Timer 2 compare output enable. 
// bit 4 		1		T1CMPOE Timer 1 Compare Output Enable. 
// bit 3-2 		00		T2PIN Polarity of GP timer 2 compare output
// bit 1-0 		00		T1PIN Polarity of GP timer 1 compare output
	

/*** COMCONA Register Configuration*/

	EvaRegs.COMCONA.all = 0x8020;
	
// bit 15 		1:		CENABLE: Compare Enable
// bit 14-13 	00:		CLD1, CLD0: CMPRx Reload Condition
// bit 12 		0:		SVENABLE: PWM Vector Enable
// bit 11-10 	00:		ACTRLD1,ACTRLD0: Action Control Regiser Reload Condition
// bit 9 		0:		FCMPOE: Full Compare Output Enable
// bit 8 		0:		PDPINTA: PDPINTA Status
// bit 7 		0:		FCMP3OE: Compare 3 Output Enable
// bit 6 		0:		FCMP2OE: Compare 2 Output Enable
// bit 5 		1:		FCMP1OE: Compare 1 Output Enable
// bit 4-3 		00:		Reserved
// bit 2 		0:		C3TRIPE: C3TRIP Enable 
// bit 1 		0:		C2TRIPE: C2TRIP Enable 
// bit 0 		0:		C1TRIPE: C1TRIP Enable 

/** ACTRA Register Configuration*/

	EvaRegs.ACTRA.all = 0x0002;
	
// bit 15 		0:		SVRDIR: PWM Vector rotate direction 
// bit 14-12 	000:	D2-D: PWM Vector basic bits
// bit 11-10 	00:		CMP6ACT1-0 Compare Action in pin 6, CMP6.
// bit 9-8 		00:		CMP5ACT1-0 Compare Action in pin 5, CMP5.
// bit 7-6 		00:		CMP4ACT1-0 Compare Action in pin 4, CMP4.
// bit 5-4 		00:		CMP3ACT1-0 Compare Action in pin 3, CMP3
// bit 3-2 		00:		CMP2ACT1-0 Compare Action in pin 2, CMP2
// bit 1-0 		10		CMP1ACT1-0 Compare Action in el pin 1, CMP1

/*** T1CON Register Configuration*/

	EvaRegs.T1CON.all = 0x9442;
	
// bit 15:14 	10:		Emulation Control bits
// bit 13 		0:		Reserved
// bit 12-11 	10:		TMODE1-TMODE0 Counter Mode Selection
// bit 10-8 	100:	TPS2-TPS0 Pre-scaler: 100= HSPCLK/16
// bit 7 		0:		T2SWT1 Timer 2 trigger by timer 1
// bit 6 		1:		TENABLE Timer Enable
// bit 5-4 		00:		TCLKS(1,0) Clock Source Selection
// bit 3-2 		00:		TCLD(1,0) Timer Compare Register Reload Condition
// bit 1 		1:		TECMPR Compare Operations Enable
// bit 0		0:		SELT1PR: Period Register Selection
						

asm( "EDIS");	//Protected Registers Write Disabled

}

/**End of function*/