Unable to program PWM M0PWM0 on the EK-TM4c123GXL LaunchPad

Hello Boca

M0PWM3 belongs to Generator 2 Generator 1 and not Generator 3 of the PWM module.

EDIT: Replaced Generator 2 by Generator 1

Regards
Amit

Amit Ashara said:

M0PWM3 belongs to Generator 2

Please hold on!   Hadn't you always (past) taught:

• Gen0  controls MxPWMx:   0 & 1
• Gen 1 controls Mx PWMx:  2 & 3

Thus poster's M0PWM3 belongs to PWMGen 1. 

Never is an apology sought nor required - outsiders "pick/choose" - you answer, "any & everything arriving/moving..."

"And - may I add a "long held" cb1_firm idea:

Would it not prove easier & less error-prone to employ this PWM Gen notation:

• PWMGenx_0   controls    PWMx_0A  &  PWMx_0B    instead of   PWMx_0  &  PWMx_1
• PWMGenx_1   controls    PWMx_1A  &  PWMx_1B    instead of   PWMx_2  &  PWMx_3
• PWMGenx_2   controls    PWMx_2A  &  PWMx_2B    instead of   PWMx_4  &  PWMx_5
• PWMGenx_3   controls    PWMx_3A  &  PWMx_3B    instead of   PWMx_6  &  PWMx_7

Forcing a different numbering scheme upon all but the very first PWM output bit causes confusion.   (proven here)  

Method shown (above) is intuitive - employs a common, numeric linkage - which is "broken" by the current (error prone) method.    Adding complexity (via the current method) - when it serves no point - is w/out merit!     (sometimes well-thought, "NIH" proves best..."Poster Guidelines" - yet another - ringing example!)

#define PWM_FREQUENCY 55000

int main()
{

    volatile uint32_t ui32LoadPW0;

    SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);

    ROM_SysCtlPWMClockSet(SYSCTL_PWMDIV_1);

//------------------------------------------------------------------

    // Setup PWM on port B5

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);

    ROM_GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_5);

    ROM_GPIOPinConfigure(GPIO_PB5_M0PWM3);

    ui32LoadPW0 = (SysCtlClockGet() / PWM_FREQUENCY) - 1;

    ROM_PWMGenConfigure(PWM0_BASE, PWM_GEN_1, PWM_GEN_MODE_DOWN);

    ROM_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1, ui32LoadPW0);

    ROM_PWMPulseWidthSet(PWM0_BASE, PWM_GEN_1, ui32LoadPW0 / 2);

    ROM_PWMOutputState(PWM0_BASE, PWM_OUT_1_BIT, true);

    ROM_PWMGenEnable(PWM0_BASE, PWM_GEN_1);

    while(1)

    {
    }

}

BocaDev said:

Here is my revised code for PB5 PWM assignment:

Where's "here?"    Ain't (here) ... this forum.   (and you claimed confusion...)

[edit]:   In the interest of, "Truth in Advertising" this reporter responded (prior) to poster's (added post) which contained code...

BocaDev said:

ROM_PWMOutputState(PWM0_BASE, PWM_OUT_1_BIT, true);

Should not that parameter be: "PWM_OUT_2_BIT?"   (Ans: mais certainement!)

Let's look @ the quicksand vendor forces us to wade thru:

GPIO_PB5_M0PWM3  is  controlled by PWM_GEN_1  and the output bit is...PWM_OUT_2_BIT!"

Seriously - are they TRYING to confuse us?   THREE DIFFERENT NUMBERS - TO DEFINE "ONE" PWM BIT... ... REALLY?    

Posters should "flood the forum - adopt cb1's SANITY-driven method!   And press for, "Poster Guidelines" - while inspired...)

TWO green verifies seem well deserved for tonight's (inspired) session...

You've proved our point, Amit. The variations in PWM: Gen, Num, & Bit defy (reasonable) understanding.
A (more) confusing method of defining 8 (simple) PWM bits could not have been developed. Nightmare.

Better yet - have not (both) you & I had (doubts) w/in this thread?   (I've not made the effort to "thumb thru" the defines - simply Nutz that is required!)

Should poster Robert arrive - and he too stumble (maybe) then this "glorious" PWM definition (cobble) has hit the "Trifecta!"  Clearly there's a much better way!

Hi Amit,

Amit Ashara said:

Since the pin is M0PWM3 shouldn't the out bit be: PWM_OUT_3_BIT?

I agree.   Yet the fact that poster, then you, and I - all "stumbled" - speaks to the severe weakness (over-complication) of this (present) PWM labeling scheme!   That's a BIG Deal!

Really - looking directly at your quote (above) "M0PWM3  "twists/turns"  and then (somehow) is "reincarnated" as, "PWM_OUT_3_BIT!"  Pardon my French - but, "that Stinks!"

Now normally you/I/Robert all support the API.   And you surely played "no part" in this overly-complex, non-intuitive, PWM label "cobble."   ("cobble" to be kind)

Earlier w/in this thread I identified that which staff/I find a, "better way:"   

Would it not prove easier & less error-prone to employ this PWM Gen notation:

• PWMGenx_0   controls    PWMx_0A  &  PWMx_0B    instead of   PWMx_0  &  PWMx_1
• PWMGenx_1   controls    PWMx_1A  &  PWMx_1B    instead of   PWMx_2  &  PWMx_3
• PWMGenx_2   controls    PWMx_2A  &  PWMx_2B    instead of   PWMx_4  &  PWMx_5
• PWMGenx_3   controls    PWMx_3A  &  PWMx_3B    instead of   PWMx_6  &  PWMx_7

Do note - this cb1 suggested,  "A & B" notation - which SO clarifies - has (already) been adopted by TM4C's Timers - has it not?  (Timer_0A & Timer_0B etc.)

The (logical - and far more intuitive) extension then - if we must have 3 labels for: (PWM Generator, PWM Gen "pair", and PWM bit) would be: PWMx_0A_bit & PWMx_0B_bit.  (added to my chart, above)

Even "poster" - admitting confusion - and heralded cb1 (in denial) MAY have (some) chance of understanding & recalling this!  (commonality & directness of these new labels adds immensely to the API's PWM clarity!)

The complexity resulting from the (very) uneven/irregular (CLUMSY) current PWM notations - deserves serious rethink - and correction.

Might it assist Amit, myself (others) to solve your issue if you'd be so good as to list:

• a simple narrative of what presently is failing.   Identify Port pin and provide your code which fully details the PWM set-up.
• always - when PWM outputs fail - we advise that the subject MCU pin be re-purposed as GPIO Output - and then set that pin high - and monitor.   Such establishes - at minimum - that when restored to PWM mode - there is (some) chance of success.
• might you switch to another MCU pin?   Perhaps there is "trouble" on the chosen pin - we'd "spin" endlessly should that be the case.
• cannot you use the same PWM module - yet a different PWM Generator - to lessen the number of variables

Your clear presentation - right here - aids our efforts.   Merci.

Hello cb1, BocaDev,

I think the following table should be a good look up for existing TivaWare define.

Regards

Amit

Hi Amit,

That surely helps.

Users should consider that the same relationships "hold" for "M1PWMn" too...

As good as your chart is, Amit - the clumsiness & distinct differences - between each (required) define, disturbs.   (clearly leads to errors)

Again - column three, "PWM_OUT_0_BIT" (could) have been represented as M0PWM0_Bit_0.   So much (more) intuitive.  And shorter.  

Building upon the existing define reinforces both - drives "home" the linkage - undoubtedly superior...

This reporter awaits the arrival of #1 "Keystone Kop" - poster Robert.  (if he can escape his corner & amusement...)

Long live labels w/extremely poor linkages and ZERO, intuitive naming.

Amit - your chart IS helpful - and appreciated - yet avoids addressing the horrendous lack of commonality & linkages - which doom user comfort!

Good morning Amit,

Thank you for your table listing showing the API signal constants for the PWM function. I followed your table and was successful in getting the PWM signal out PB5.

Here is the code listing for anyone interested.

int main()
{
	ROM_SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);
	ROM_SysCtlPWMClockSet(SYSCTL_PWMDIV_1);
	
	// Configure Port B Pin 5 for PWM
	ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
	ROM_GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_5);
	ROM_GPIOPinConfigure(GPIO_PB5_M0PWM3);
	
	ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);		// Enable PWM Module 0
	
	//------------------------------------------------------------------
	// Setup PWM0 on port B5 (GPIO_PB5_M0PWM3)
	
	uint32_t LoadPW0 = (SysCtlClockGet() / 55000) - 1;
	
	ROM_PWMGenConfigure(PWM0_BASE, PWM_GEN_1, PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
	ROM_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1, LoadPW0);
	ROM_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_3, LoadPW0 / 2);
	
	ROM_PWMOutputState(PWM0_BASE, PWM_OUT_3_BIT, true);
	ROM_PWMGenEnable(PWM0_BASE, PWM_GEN_1);	
	
	
	while(1)
	{
		
	
	}
}

Thanks again Amit for the time you spent in coming up with your straight-forward table.

Regards,
BoceDev