jokkebk:

Cool, this post got featured on Hack a Day!

scompo:

As far as I know the pwm can generate interrupts just on compare, not on reset of the counter.
I’ve asked about it in the TI forums along with a question on the TimerSynchronize() function, right here: . Do you have any idea about how that works?

proteinman:

Thanks for putting this out there, it helped me alot.

proteinman:

//This code will PWM the leds

#include “inc/hw_types.h”
#include “inc/hw_memmap.h”

#include “driverlib/sysctl.h”
#include “driverlib/gpio.h”
#include “driverlib/timer.h”
#include “driverlib/pin_map.h”

int main(void) {
unsigned long ulPeriod_led_f1, dutyCycle_led_f1, ulPeriod_led_f2, dutyCycle_led_f2, ulPeriod_led_f3, dutyCycle_led_f3;

// 40 MHz system clock
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|
SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);

ulPeriod_led_f1 = 1000;
dutyCycle_led_f1 = 1;
ulPeriod_led_f2 = 1000;
dutyCycle_led_f2 = 1;
ulPeriod_led_f3 = 1000;
dutyCycle_led_f3 = 1;

// Turn off LEDs
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0);

// Configure LEDs PortF as Timer outputs -> see pg 659 of datasheet
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
GPIOPinConfigure(GPIO_PF1_T0CCP1|GPIO_PF2_T1CCP0|GPIO_PF3_T1CCP1);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);

// Configure timer 0 – this timer outputs to pf1 (led)
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR|TIMER_CFG_B_PWM);
TimerLoadSet(TIMER0_BASE, TIMER_B, ulPeriod_led_f1 -1);
TimerMatchSet(TIMER0_BASE, TIMER_B, dutyCycle_led_f1); // PWM
TimerEnable(TIMER0_BASE, TIMER_B);

//Configure timer 1 – timer is split in half; A and B timers (16 bit)
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER1);
TimerConfigure(TIMER1_BASE, TIMER_CFG_SPLIT_PAIR|TIMER_CFG_A_PWM|TIMER_CFG_B_PWM);

//Values and settings for Timer1(A) – this timer outputs to pf2
TimerLoadSet(TIMER1_BASE, TIMER_A, ulPeriod_led_f2 -1);
TimerMatchSet(TIMER1_BASE, TIMER_A, dutyCycle_led_f2); // PWM
TimerEnable(TIMER1_BASE, TIMER_A);

//Values and settings for Timer1(B) – this timer outputs to pf3
TimerLoadSet(TIMER1_BASE, TIMER_B, ulPeriod_led_f3 -1);
TimerMatchSet(TIMER1_BASE, TIMER_B, dutyCycle_led_f3); // PWM
TimerEnable(TIMER1_BASE, TIMER_B);

while(1) { // The following code varies the duty cycle over time, it cycles duty cycles at different rates
TimerMatchSet(TIMER0_BASE, TIMER_A, dutyCycle_led_f1++);
TimerMatchSet(TIMER1_BASE, TIMER_A, dutyCycle_led_f2=dutyCycle_led_f2+2);
TimerMatchSet(TIMER1_BASE, TIMER_B, dutyCycle_led_f3=dutyCycle_led_f3+4);

if(dutyCycle_led_f1 >= ulPeriod_led_f1 – 1)
dutyCycle_led_f1 = 0;

if(dutyCycle_led_f2 >= ulPeriod_led_f2 – 1)
dutyCycle_led_f2 = 0;

if(dutyCycle_led_f3 >= ulPeriod_led_f3 – 1)
dutyCycle_led_f3 = 0;

SysCtlDelay(200000);
}
}

scompo:

A solution to fire both interrupts on capture and on timer reset would be to use 2 syncronized timers one as PWM and the other just as a periodic one as suggested .

jokkebk:

Thanks for your input! Sorry that your comments took some time to appear, for some reason Akismet thought they were spam, which they definitely were not. :)

GMB:

Thank you!
Have you tried this code?
There is something wrong!

JimBob:

You might want to check out the Stellaris PinMux utility on the TI website. It helps in setting up the alternate pin functions. I have found the learning curve for Stellaris steep, owing largely to a dearth of (clear) documentation. Your example also cleared up an issue I just ran into while using the UARTs-some constants used by the pin mapping were indefined even though the compiler was finding the include file. One would assume that specifying the chip when the project was created would have resulted in PART_LM4F120H5QR being defined. Apparently not so. I cannot see any reason for this not being an automatic feature.

Labeeb:

What compiler are you using?It looks like you are using etheir CCS or IAR, this code is not compatible with etheir oneyou may have to enable the interrupt another way (gie bit), and you will have to change how the interrupt is called (#pragma)please let me know how you get it to work and i will update my post to add your changes

Astro75:

I made more user friendly methods for controlling pwm.
https://github.com/astro75/stellaris-pwm/blob/master/main.c

M.Fatih İNANÇ:

Hello,

The wrong line is;
GPIOPinConfigure(GPIO_PF1_T0CCP1|GPIO_PF2_T1CCP0|GPIO_PF3_T1CCP1);

It should be as follows;
ROM_GPIOPinConfigure(GPIO_PF3_T1CCP1);
ROM_GPIOPinConfigure(GPIO_PF2_T1CCP0);
ROM_GPIOPinConfigure(GPIO_PF1_T0CCP1);

And good point to add invert outputs;
// invert PWM outputs
TIMER0_CTL_R |= 0x4000;
TIMER1_CTL_R |= 0x4000;
TIMER1_CTL_R |= 0x40;

Misael Lafuente:

Thanks I was very helpfull for me. I also spended so much time trying to configure the PWM output

Ivan Babatov:

Here is how I managed to use interrupts with timer0 in PWM mode. Hope it helps.

in main(void) :

/*#include all necessary headers from previous examples */
#include “inc/hw_timer.h” /* to gain access to TIMER_O_TAMR, etc. timer registers */

/* As in the previous examples – setup clock, enable used peripherals, setup GPIOs here */

TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_PWM | TIMER_CFG_B_PWM);

/* Make corresponding CCP pin go HIGH (going LOW is the default legacy operation) in the beginning of the PWM period (TAPLO = 1)
* (not really needed if we only care for interrupts);
* Make the changes to match registers take effect on the start of the next PWM period, not immediately (TAMRSU = 1);
* Make the changes to reload (period) registers take effect on the start of the next PWM period, not immediately (TAILD = 1);
*
* NOTE: the PWM with interrupts should work even without this line, but the datasheet says it’s better to set the MR this way */
HWREG(TIMER0_BASE + TIMER_O_TAMR) |= (TIMER_TAMR_TAMRSU | TIMER_TAMR_TAPLO | TIMER_TAMR_TAILD);

/* Make the timer generate events on both rising and falling PWM edges */
TimerControlEvent(TIMER0_BASE, TIMER_A, TIMER_EVENT_BOTH_EDGES);

/* Setup interrupts */
TimerIntEnable(TIMER0_BASE, TIMER_CAPA_EVENT);
IntEnable(INT_TIMER0A);
IntMasterEnable();
TimerEnable(TIMER0_BASE, TIMER_A);
while(1)
{
/* main loop here */
}

Ivan Babatov:

Wrong again :( :(
Last attempt, if this does not work, please erase all the mess and mail me to (address removed) – I will send you the project.

void Timer0IntHandler(void)
{
uint32_t tmr_val;
uint32_t tmr_match;
uint32_t InterruptStatus = TimerIntStatus(TIMER0_BASE, true);

Ivan Babatov:

Ah, this time it’s OK. I really hope this will be of some use to someone :)

Ivan Babatov:

Please, look below for the Timer ISR

Anthony:

Thank you very much I was able to get this working but may I ask for future reference…What is the point of defining the symbol “PART_LM4F120H5QR” ? Is it so that the compiler knows which device to look under in the pin_map? That’s just my wild guess since I was finding that CSS kept telling me GPIO_PF1_T0CCP1 was an unrecognized symbol up until I pre-defined the PART_LM4F120H5QR symbol in the project options.

igor:

There is an error in the tutorial code

under Step 1: Setting up the timer0 PWM mode

In the second code box dutyCycle is never used.

I believe the line that reads
TimerMatchSet(TIMER0_BASE, TIMER_A, ulPeriod / 2);
should read
TimerMatchSet(TIMER0_BASE, TIMER_A, dutyCycle);
as it does in the final code box.

Greg Oberfield:

It’s so that the proper pin mappings from pin_map.h are pulled into the project. Believe me, took a little bit for me to figure that out the first time until I looked in the file, saw all the defines and went “aww hell!”

Savita:

Hey all!. This one has helped me a lot. i want to do a down counter. So i need to use TimerB of the timer0 and use the same way as above?

Barty79:

To configure interrupts for PWM:

TimerIntEnable(TIMER0_BASE, TIMER_CAPA_EVENT);
TimerControlEvent(TIMER0_BASE, TIMER_A, TIMER_EVENT_POS_EDGE);
TimerIntRegister(TIMER0_BASE, TIMER_A, Timer0AIntHandler);

void Timer0AIntHandler(void) {
TimerIntClear(TIMER0_BASE, TIMER_EVENT_POS_EDGE);
...
}


Barty79:

Sorry, it should be:

void Timer0AIntHandler(void) {
TimerIntClear(TIMER0_BASE, TIMER_CAPA_EVENT);
...
}


Lippy:

Hey I love this tutorial!!! Great work. I do have two questions though.

1. Can you change the frequency of the PWM wave? Currently mines is at 40 kHz which is great but it would be nice to change the frequency for applications like servo driving.

2. Can you achieve a 0% duty cycle? when I enter in 0% (1000) the PWM wave goes to 100% (3.3V)

Thanks for your help

Lippy:

Excuse my stupidity, for some reason I completely missed ulPeriod lol

Brandon:

Thanks for the detailed write-up!

Dutchpainter:

I had the same problem, changed the mentioned line to:


GPIOPinConfigure(GPIO_PF1_T0CCP1);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_1);
GPIOPinConfigure(GPIO_PF2_T1CCP0);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_2);
GPIOPinConfigure(GPIO_PF3_T1CCP1);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_3);


that seems to work. See also page 159 of the Stellaris Peripheral Driver Library

jokkebk:

Thanks for noticing that. Fixed it now.

jokkebk:

Yes, one would assume the correct part constant is defined by other include files based on build target platform (one needs to set it when creating project, anyways), but no, you actually have to define that yourself. Very counterintuitive and there’s no mention of that in the documentation..

Larissa:

Just wanted to say thank you so much for such a detailed and throughout write-up.
Side note: We did include the PWM in the next revision of the board :-), but this helps give all of the Stellaris ones in the ecosystem a way to do it!

Thank you again!

Emmanuel:

Thank you very much. I really needed the info

José Tejero:

The wrong is

while(1) { // The following code varies the duty cycle over time, it cycles duty cycles at different rates
TimerMatchSet(TIMER0_BASE, TIMER_A, dutyCycle_led_f1++);

It should be

while(1) { // The following code varies the duty cycle over time, it cycles duty cycles at different rates
TimerMatchSet(TIMER0_BASE, TIMER_B, dutyCycle_led_f1++);

yakdag:

both GPIOPinConfigure(GPIO_PF1_T0CCP1|GPIO_PF2_T1CCP0|GPIO_PF3_T1CCP1); and ROM_GPIOPinConfigure(GPIO_PF3_T1CCP1);
ROM_GPIOPinConfigure(GPIO_PF2_T1CCP0);
ROM_GPIOPinConfigure(GPIO_PF1_T0CCP1); is same mistake; #20 identifier “GPIO_PF3_T1CCP1” is undefined

what would be problem. I’m stuck here. ı m using CCS 5.3

prasad chitta:

hi….
I need a small nformation, Is pwm code of stellaris launch pad work on c2000 launch pad…?

Dasaev:

Hi Ivan, may you send me your project please. I need it
Thank you

Ivan Babatov:

Hi,
I will gladly send you the project, I just need to get home – its on the PC there. However…. I would need your e-mail, and I am afraid this site won’t let you publish it. Try mailing me at babatowatyahoodotcom (hope this does not get filtered).
Looking forward to hearing from you,
Ivan.

Sam:

Having the same error: GPIO_PF3_T1CCP1 is undefined. Any ideas?