AN2618 datasheet(13/23 Pages) STMICROELECTRONICS

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AN2618

Code example 3.etpuc_pwm.c

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Appendix C

Code example 3.etpuc_pwm.c

#include <etpuc_PWM.h>

/*--------------------------------------------------------------------+

Global Variable Definitions

+--------------------------------------------------------------------*/

int DutyCycle = 500;

/********************************************************************************

* FUNCTION: PWM

* PURPOSE:

This is the eTPU function that modulate an eTPU output pin as PWM

signal based on the host service request and the parameters passed

from the host.

* INPUTS NOTES: This function has 2 parameters

* RETURNS NOTES: N/A

* WARNING:

********************************************************************************/

void PWM(int Period, unsigned fract24 Duty)

{

static int StartTimeHi;

int HighTime;

if (hsr == hsrInitPWM)

// Init PWM HSR -- Required to initialize the signal.

{

InitPWM:

SetChannelMode(em_nb_dt);

SetupMatch_B(tcr1, Mtcr1_Ctcr1_ge, low_high);//set output high immediately

}

else if (matchA_transB)// Here on Match1 (falling edge)

{

FallingMatch:

ClearMatchALatch();

SetupMatch_B((StartTimeHi + Period), Mtcr1_Ctcr1_ge, low_high); //set up for

rising match

}

else if (matchB_transA) // Here on Match2 (rising edge)

{

RisingMatch:

ClearMatchBLatch();

StartTimeHi = GetCapRegB();

// Store the time the pulse transition to high

if (Duty == 0xffffff) // Special case for 100% modulation

{

HighTime = 32 ; // arbitrary value having no efect on the output signal

SetupMatch_A(HighTime, Mtcr1_Ctcr1_ge, match_no_change);

}

else

{

HighTime = Period * Duty + StartTimeHi;

SetupMatch_A(HighTime, Mtcr1_Ctcr1_ge, high_low);

//setup for falling

match

}

else

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