TM4C123G PWM 80 MHz

Hello Prashant,

It would be more useful if you have the code posted as well what "distorted" looks like and clean signal looks like?

Regards

Amit

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_gpio.h"
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/pin_map.h"
#include "driverlib/gpio.h"
#include "driverlib/pwm.h"

int
main(void)
{ unsigned long ulPeriod;

//Set the clock
SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); //for 40 MHz
// SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); //for 80MHz

//Configure PWM Clock to match system
SysCtlPWMClockSet(SYSCTL_PWMDIV_1);

// Enable the peripherals used by this program.
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM1); //The Tiva Launchpad has two modules (0 and 1). Module 1 covers the LED pins
ulPeriod = SysCtlClockGet() / 1000000; //PWM frequency

//Configure PF1,PF2,PF3 Pins as PWM

GPIOPinConfigure(GPIO_PF1_M1PWM5);
GPIOPinConfigure(GPIO_PF2_M1PWM6);
GPIOPinConfigure(GPIO_PF3_M1PWM7);
GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3);

//Configure PWM Options
//PWM_GEN_2 Covers M1PWM4 and M1PWM5
//PWM_GEN_3 Covers M1PWM6 and M1PWM7 See page 207 4/11/13 DriverLib doc
PWMGenConfigure(PWM1_BASE, PWM_GEN_2, PWM_GEN_MODE_UP_DOWN | PWM_GEN_MODE_NO_SYNC);
PWMGenConfigure(PWM1_BASE, PWM_GEN_3, PWM_GEN_MODE_UP_DOWN | PWM_GEN_MODE_NO_SYNC);

//Set the Period (expressed in clock ticks)
PWMGenPeriodSet(PWM1_BASE, PWM_GEN_2, ulPeriod);
PWMGenPeriodSet(PWM1_BASE, PWM_GEN_3, ulPeriod);

//Set PWM duty-50% (Period /2)
PWMPulseWidthSet(PWM1_BASE, PWM_OUT_5,ulPeriod/(100/30));
PWMPulseWidthSet(PWM1_BASE, PWM_OUT_6,ulPeriod/2);
PWMPulseWidthSet(PWM1_BASE, PWM_OUT_7,ulPeriod/2);

// Enable the PWM generator
PWMGenEnable(PWM1_BASE, PWM_GEN_2);
PWMGenEnable(PWM1_BASE, PWM_GEN_3);

// Turn on the Output pins
PWMOutputState(PWM1_BASE, PWM_OUT_5_BIT |PWM_OUT_6_BIT|PWM_OUT_7_BIT, true);

//Do nothing
while(1)
{

}

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

for 80 MHz system clock and 1MHz PWM , output waveform is of 1.33 MHz

But for 40MHz system clock and 1MHz PWM , output waveform is of 1MHz accurate. 

hiii amit

thank you. so how can i use 80 MHz clock? 

Hello Prashant,

To get 80MHz clock you would need to use the API as

SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL| SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);

And instead of using the return value of SysCtlClockGet use the fixed value of 80000000 assigned to the variable that was previously getting the value from the SysCtlClockGet API

Regards

Amit

hii amit

I am using this.

SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL| SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);

instead of

ulPeriod = SysCtlClockGet() / 1000000;

i am using

ulPeriod = 80000000/ 1000000;

but still i am not able to get 80MHz clock.

Regards

Prashant

Hello Prashant

Is the crystal you are using 16MHz? And you are measuring the 80MHz by looking at the PWM output?

Regards

Amit

hii amit.

yes i am using 16 MHz crystal. I am not measuring 80 MHz. I am seeing quality of PWM output. at 80 MHz should be better than that of pwm at 16 MHz.

Hello Prashant,

I can try this on my EK-TM4C123GXL LaunchPad. Will post reply after testing.

Regards

Amit

hii amit

thank you. will be waiting.

Regards

Prashant