tm4c1294 pwm

Bryce Smith said:

Does any (one) have some basic code for the tm4c1294 launchpad

Far simpler is use of one of the MCU's Timers - configured into PWM mode.

Two caveats (restrictions) may apply:

a) your board may not directly route a timer output to an "on board" Led.  (you'll likely have to do that)

b) PWM Generator provides much more command/control  capability

For your expressed, "Switch control of PWM Duty Cycle" use of a Timer (as described) provides a greatly eased & speeded solution.

(we should note that PWM usually operates at frequencies well above those employed to "blink" an Led...)

Thanks i had given some consideration to using a timer. But i am primarily focused on familiarizing myself with the boards PWM modules.

I was hoping to use PWM to dim/brighten the leds. Any basics for that?

Bryce Smith said:

use PWM to dim/brighten the leds. Any basics for that?

Well yes - there are "basics" - but if you miss set-up/config you may spend days in frustration.

Our findings - most all "shortcuts" achieve the opposite!    Amit has guided you to the "slow, steady" code examples - which usually - but not always - insure that your set-up & config. are full & proper.

Look (but not at bedtime) at the PWM section of the MCU Manual, too.   It's well written - but oozes with detail - it is nether a "quick nor pleasant" read.   Again - unless you're far smarter/gifted than most here - be prepared to "invest the time" to read and code - and repeat that process.

We find that "feedback" either via an Led - but far better from even a simple scope - will help immensely.    Run your PWM at 100Hz or so in the beginning - going faster adds complications - later is time enough for tweaking.

Again - the Timer should prove a 10 times (or more) faster/easier means to PWM Leds.    All the key/critical benefits of the PWM Generators are primarily reserved for their use in tandem (a la 3 phase BLDC motor, or power switching/generation) and not really/fully/properly harnessed by an Led...

Thanks. Yes the end game here is to use the board to do MPPT through PWM for a small underwater rotor... however i cannot even get the PWM modules to work for me. I tried using this code from another forum that you commented on https://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/379458 

the compiler says that  its having trouble with this portion 

    GPIOPinConfigure(GPIO_PA6_M1PWM2);

    GPIOPinConfigure(GPIO_PF0_M1PWM4);

    GPIOPinConfigure(GPIO_PF1_M1PWM5);

    GPIOPinConfigure(GPIO_PF2_M1PWM6);

    GPIOPinConfigure(GPIO_PF3_M1PWM7);

that the GPIO_Pnn_MnPWMn isn't defined... why is this happening?

My friend - too often the "lure" of the  End Game intrudes upon the necessity of building an adequate, "Beginning Game."

Have you read and programmed the PWM example which vendor's Amit referenced?   If not - "blind copying" of another's code - proves ineffectual - just as you report.    When you report, "cannot even get the PWM modules to work" - what does that really mean?   (I can quickly/easily think of at least 3 PWM "issues.")

You should avoid use of PF0 or PD7 at this stage - and you should model your code after the example aleady provided.  

Earlier you were "alerted" to the fact that PWM Generator set-up & configuration is detailed & demanding.    And the "copy/paste code" you now present - provides only a "partial PWM initialization."  

Devil is in the detail w/these MCUs - they're powerful but "shortcuts" - as you're discovering - are unlikely to ease - fully work or (even) "shorten."

And - of course (and always) "avoid like the plague" any attempt @ PF0 or PD7 - both "blessed" by "special needs..."

KISS dictates that you set-up/config only a single PWM Output - focus just on that - to speed, simplify & enhance your results.   Too much, too soon - never good - seldom succeeds.   (but great at introducing "FUD!")
 
We note you've not once described how you are "monitoring" the MCU's output. Are you absolutely sure you're probing the correct pin - and that the chosen pin does indeed - reach a board-edge header?

ah thanks very much. How do i configure the GPIO to be PWM Pins?

is it something like this?

ahhhh. so it didn't like the line ROM_GPIOPinConfigure(GPIO_PB6_M0PWM0); still....:

"#20 identifier "GPIO_PB2_M0PWM0" is undefined"

ps. i used b2 and b3 as they were mor easily accessible.

Heres the code as is. i looked in the header files and there is no definition for GPIO_PB2_M0PWM0... =/ i have no idea how to resolve this

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/*Program to implement PWM, then perhaps make LED's dim and brighten, then modify the pulse width with the buttons*/
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_memmap.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/pwm.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"
#include "drivers/pinout.h"
#include "driverlib/rom_map.h"

//system clock variable
uint32_t g_ui32SysClock;

int main(void){

/*1. set the system clock.. etc.
* >> Enable the PWM Module in the System Control using SysCtlPeripheralEnable, Enable the corresponding GPIO's as well
* >> Configure the GPIO to be PWM Pins
* 2. set the PWM clock from the system clock; PWMClockSet(PWM1_BASE, PWM_SYSCLK_DIV_1)
* 4. configure The PWM generator; PWMGenConfigure(PWM1_BASE, PWM_GEN_1,PWM_GEN_MODE_NO_SYNC)
* 5. set the period for the generator; PWMGenPeriodSet(PWM1_BASE, PWM_GEN_1, some unsigned long that is the period)
* 6. enable PWM outputs; PWMOutputState(PWM1_BASE, PWM_OUT_n_BIT, TRUE) where n is 0-7
* 7. set the pulse width; PWMPulseWidthSet(PWM1_BASE, PWM_OUT_2, unsigned long (ex. period/2))
* 3. enable the PWM Generator; PWMGenEnable(PWM1_BASE, PWM_GEN_1)*/

//1. set the clock to run off of crystal at 25Mhz
g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN \
| SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480), 120000000);

//2. Enable the PWM Module in the System Control using
//enable peripheral (port N)
//configure pin as a PWM pin
SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
GPIOPinTypePWM(GPIO_PORTB_BASE, GPIO_PIN_2 | GPIO_PIN_3);




>>>>>>>>>>>PROBLEM LINE>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>GPIOPinConfigure(GPIO_PB2_M0PWM0);




//3. Set the pwm clock to the system clock/16
PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_16);

//4. Configure the PWM generator
PWMGenConfigure(PWM0_BASE, PWM_GEN_0, PWM_GEN_MODE_NO_SYNC);

//5. Set the period for the generator
//set pwm to run at 100hz . (N = (1 / f) * SysClk) ; (1 / 100Hz) * (120MHz/16) = 75000 cycles
unsigned long period = 75000;
PWMGenPeriodSet(PWM0_BASE, PWM_GEN_0, period);

//6. Enable the PWM outputs
// Enable the PWM0 Bit 0 (PB2) and Bit 1 (PB3) output signals.
PWMOutputState(PWM0_BASE, (PWM_OUT_0_BIT | PWM_OUT_1_BIT), true);

//7. set the pulse width
PWMPulseWidthSet(PWM0_BASE, PWM_OUT_0, (period/2));

//8. Enable the PWM Generator
PWMGenEnable(PWM0_BASE, PWM_GEN_0);
/*
FOR COMPARISON!:
ROM_PWMGenConfigure(PWM0_BASE, PWM_GEN_0,

ROM_PWMGenPeriodSet(PWM0_BASE, PWM_GEN_0

ROM_PWMPulseWidthSet(PWM0_BASE, PWM_OUT_0,

ROM_PWMGenEnable(PWM0_BASE, PWM_GEN_0

ROM_PWMOutputState(PWM0_BASE, (PWM_OUT_0_BIT | PWM_OUT_1_BIT*/


}

I'm not so sure that adding the complexity (and diversion) demanded by the use of PF0 makes great sense.    Instead - should you not (now) be able to some way/how find an appropriate PWM pin - and properly define it?   That's (really) all that's missing - isn't that so?

Code extract I provided (which I listed as, "hope for universal") should work for LX4V & TM4C123 - but alas not your device.   (I recall your "ban" of 123 code - but in the "heat of battle" I thought a past, proven code dump "might" escape your wrath...

To assist you in finding - then properly defining a PWM pin - here's how my firm went about that process:  (following directly from MCU datasheet)

Thus - for TM4C (or LX4F) PB6 is indeed PWM Gen0's, 0 bit.    You are not forced to use that bit - and best that you "stick w/ PWM Gen0" - so as not to seriously disrupt my detailed code example.   Yet again - fighting the "endless" PF0 battle - steers you far from the PWM issue.   Seems an unnecessary & destructive diversion.

You merely (now) have to choose an accessible bit (one "not" on the "banned bits list") - define it properly - and that should get you (at last) "On the Air."