Can't make GPIO_PF0_M1PWM4 pwm output work

Paul GML

Hello,

I'm trying to get M1PWM2-5 working on a LM4F232H5QD (EK-LM4F232 Keil). I can get PA6, PA7 and PF1

working but can't get any signal from PF0. I have tried everything I could think of and still no luck.

Can anyone please go through this and tell me if there is something wrong with this code? Thanks!

	// set pwm system clock
	SysCtlPWMClockSet(SYSCTL_PWMDIV_1);

	// enable peripherals
	SysCtlPeripheralEnable(SYSCTL_PERIPH2_GPIOA);
	SysCtlPeripheralEnable(SYSCTL_PERIPH2_GPIOF);
	SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM1);

	// enable alternate function
	GPIOPinConfigure(GPIO_PA6_M1PWM2);
	GPIOPinConfigure(GPIO_PA7_M1PWM3);
	GPIOPinConfigure(GPIO_PF0_M1PWM4);
	GPIOPinConfigure(GPIO_PF1_M1PWM5);

	// configure pads
	GPIOPinTypePWM(GPIO_PORTA_BASE, GPIO_PIN_6 | GPIO_PIN_7);
	GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_0 | GPIO_PIN_1);

	// configure PWM generators
	PWMGenConfigure(PWM1_BASE, PWM_GEN_1, PWM_GEN_MODE_UP_DOWN | PWM_GEN_MODE_NO_SYNC);
	PWMGenConfigure(PWM1_BASE, PWM_GEN_2, PWM_GEN_MODE_UP_DOWN | PWM_GEN_MODE_NO_SYNC);

	// set PWM generators periods
	PWMGenPeriodSet(PWM1_BASE, PWM_GEN_1, 1666);
	PWMGenPeriodSet(PWM1_BASE, PWM_GEN_2, 1666);

	// set pulse width
	PWMPulseWidthSet(PWM1_BASE, PWM_OUT_2, 1666 / 2);
	PWMPulseWidthSet(PWM1_BASE, PWM_OUT_4, 1666 / 2);

	// enable deadband
	PWMDeadBandEnable(PWM1_BASE, PWM_GEN_1, 10, 10);
	PWMDeadBandEnable(PWM1_BASE, PWM_GEN_2, 10, 10);

	// enable PWM bits
	PWMOutputState(PWM1_BASE, PWM_OUT_2_BIT | PWM_OUT_3_BIT | PWM_OUT_4_BIT | PWM_OUT_5_BIT, true);

	// enable the generators
	PWMGenEnable(PWM1_BASE, PWM_GEN_1);
	PWMGenEnable(PWM1_BASE, PWM_GEN_2);

	// sync the time base (execute after enabling generators)
	PWMSyncTimeBase(PWM1_BASE, PWM_GEN_1_BIT | PWM_GEN_2_BIT);

over 12 years ago

0 cb1_mobile over 12 years ago

Guru 117855 points

You have bumped against one of this new MCU's errata - PF0 is an NMI pin (defaults to such) - must receive "special treatment" to re-purpose.

W/in the GPIO chapter the Unlock method is described - once you've unlocked pin PF0 you can repurpose it to your PWM selection. You then re-lock the pin and it will retain your desired PWM mode.

We encountered this issue when attempting to use PF0 on a variant 4F MCU - in our case we employed PF0 as an Analog Comparator output.

Prefer you to review the MCU datasheet - if you have further issues will assist as/if/when able...

0 Paul GML over 12 years ago in reply to cb1_mobile

Prodigy 80 points

Thank you. For anyone else having the same problem, this has solved the problem:

// enable peripherals
SysCtlPeripheralEnable(SYSCTL_PERIPH2_GPIOF);

// unlock GPIO PF0
GPIO_PORTF_LOCK_R = GPIO_LOCK_KEY;
GPIO_PORTF_CR_R = GPIO_PIN_0;

// enable alternate function
GPIOPinConfigure(GPIO_PF0_M1PWM4);

0 cb1_mobile over 12 years ago in reply to Paul GML

Guru 117855 points

Paul GML said:
GPIO_PORTF_LOCK_R = GPIO_LOCK_KEY;

Glad to have assisted - the many new benefits afforded by these new MCUs sometimes add complexity.

However - our unlocking code is different: (shown is extract from hw_gpio.h, Rev 8555 - which I believe to be most current release) In our case we employed GPIO_LOCK_KEY_DD

// The following are defines for the bit fields in the GPIO_O_LOCK register.
//
//*****************************************************************************
#define GPIO_LOCK_M             0xFFFFFFFF // GPIO Lock
#define GPIO_LOCK_UNLOCKED      0x00000000 // The GPIOCR register is unlocked
                                            // and may be modified
#define GPIO_LOCK_LOCKED        0x00000001 // The GPIOCR register is locked
                                            // and may not be modified
#define GPIO_LOCK_KEY           0x1ACCE551 // Unlocks the GPIO_CR register
#define GPIO_LOCK_KEY_DD        0x4C4F434B // Unlocks the GPIO_CR register on
                                            // DustDevil-class devices and
                                            // later

Beyond this - we attended to GPIO_O_AFSEL & GPIO_O_DEN - while the device was "unlocked" - to achieve our desired re-purpose functionality.

May prove of value to learn the actual value of your, "GPIO_LOCK_KEY." (w/in IAR we just highlight the expression and then "go to definition" reveals...)

0 Moises Escobedo over 10 years ago in reply to cb1_mobile

Prodigy 185 points

Hello guys,

Thank you for the post.

We could not figured out why MIPWM4 on PORTF PIN 0 was not working

and finally come across your post. Our problem was related to the new TIVA C parts,

TM4C123 parts but same concept applied and it worked.

Here is how we got the PORTF PIN 0 or F0 unlock and configure for PWM function.

    //
   //    GPIO_PF0 is a NMI pin that must be unlock
   //
    // unlock GPIO PF0
    HWREG(GPIO_PORTF_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY;
    HWREG(GPIO_PORTF_BASE + GPIO_O_CR) = GPIO_PIN_0;

   // enable alternate function
    ROM_GPIOPinConfigure(GPIO_PF0_M1PWM4);       //PWM4

I hope this is helpful to some one as it was for us.

0 cb1_mobile over 10 years ago in reply to Moises Escobedo

Guru 117855 points

@ Moises,

Very nice that you expanded upon this earlier issue - should help many - thank you.

Should state that earlier use of: "GPIO_LOCK_KEY_DD" - which worked for us - has been "deprecated" and your use of, "GPIO_LOCK_KEY" is now appropriate and proper.

Great that you "searched" the forum - and that you cared enough to share your findings to the benefit of many others... Someday/some planet - MCU manuals will "adopt" long urged suggestion to, "better highlight" the identification of NMI pins - and corrective actions required to, "their repurpose."

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Can't make GPIO_PF0_M1PWM4 pwm output work