EK-TM4C1294XL timer query

Khalid Mirza38

Other Parts Discussed in Thread: EK-TM4C1294XL

Dear All,

I am programming the EK-TM4C1294XL. I am using the timer.c example from the list of examples provided by TI. The timer in that example has an interrupt of 1seconds. I was aimiing to have the timer interrupt at every 4 microsecond. The minimum interrupt time I was able to achieve was 2.3 ms.

Can anyone please explain how why this is the case and how I can achieve lower interrupt time ?

Thanks in advance

over 10 years ago

0 Amit Ashara over 10 years ago

TI__Guru**** 244440 points

Hello Khalid

Can you please share the code which is giving an interrupt at 2.3ms instead of expected 4 us?

Regards
Amit

0 Khalid Mirza38 over 10 years ago in reply to Amit Ashara

Prodigy 70 points

Hello Amit,

I set the clock at 12 MHz from the following code :

g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
SYSCTL_OSC_MAIN |
SYSCTL_USE_PLL |
SYSCTL_CFG_VCO_480), 120000000);
I configure the timer as usual... I then set the load value of the timer as :

ROM_TimerLoadSet(TIMER0_BASE, TIMER_A, 480 ); g_ui32SysClock/

If I use the above line as follows, then the interval is 1 second

ROM_TimerLoadSet(TIMER0_BASE, TIMER_A, g_ui32SysClock );

thanks

Khalid

0 Khalid Mirza38 over 10 years ago in reply to Khalid Mirza38

Prodigy 70 points

Hello Amit,

Sorry I made some mistakes in my last post, so posting again after correction :

I set the clock at 120 MHz from the following code :

g_ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
SYSCTL_OSC_MAIN |
SYSCTL_USE_PLL |
SYSCTL_CFG_VCO_480), 120000000);
I configure the timer as usual... I then set the load value of the timer as :

ROM_TimerLoadSet(TIMER0_BASE, TIMER_A, 480 );

If I use the above line as follows, then the interval is 1 second

ROM_TimerLoadSet(TIMER0_BASE, TIMER_A, g_ui32SysClock /2);

thanks

Khalid

0 Amit Ashara over 10 years ago in reply to Khalid Mirza38

TI__Guru**** 244440 points

Hello Khalid

Setting the timer load to g_ui32SysClock /2 would not be 1 second but 0.5 sec

Setting the timer load to 480 will produce a timer interval of 4us. But then how are you toggling the pin, via interrupt?

Regards
Amit

0 Khalid Mirza38 over 10 years ago in reply to Amit Ashara

Prodigy 70 points

Hi Amit.

Yes that's right, it will be 0.5 s.

I am toggling the pin via interrupt. The code is given below :

void
Timer0IntHandler(void)
{
//
// Clear the timer interrupt.
//
ROM_TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);

//
// Toggle the flag for the first timer.
//
HWREGBITW(&g_ui32Flags, 0) ^= 1;

//
// Use the flags to Toggle the LED for this timer
//
GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, g_ui32Flags);

//
// Update the interrupt status.
//
ROM_IntMasterDisable();
ROM_IntMasterEnable();

}

0 Khalid Mirza38 over 10 years ago in reply to Amit Ashara

Prodigy 70 points

Hello Amit,

Will it be possible for you to send some pre-tested code to achieve this ? If yes, could you please share it ?

Regards,
Khalid

0 Amit Ashara over 10 years ago in reply to Khalid Mirza38

TI__Guru**** 244440 points

Hello Khalid

You do not need to do the following

//
// Toggle the flag for the first timer.
//
HWREGBITW(&g_ui32Flags, 0) ^= 1;

//
// Use the flags to Toggle the LED for this timer
//
GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, g_ui32Flags);

//
// Update the interrupt status.
//
ROM_IntMasterDisable();
ROM_IntMasterEnable();

Instead it can be made as.

GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, ~(GPIOPinRead(GPIO_PORTN_BASE, GPIO_PIN_0)));

Regards
Amit