TM4C129DNCPDT: Timer counter without interrupt

Hi, Charles thank you for help.

    Actual Charles i am measuring pulse with of 10us to 150us. Most of the time i am getting very close value like 12us/11us/10us. But sometime i am getting 20us/17us. one or two sample(pulse width) out off 10 sample(pulse width) i am getting like this. I am following your suggest example (C:\ti\TivaWare_C_Series-2.2.0.295\examples\boards\ek-tm4c1294xl\timer_edge_capture). I am using only one Timer. we are generating pulse from Function generator.

How to solve this problem?

Please Check my configuration once.

void timer_Init(void)
{
MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);

while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_TIMER0))
{

}
MAP_TimerClockSourceSet(TIMER0_BASE, TIMER_CLOCK_SYSTEM);
MAP_TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC_UP);
MAP_TimerLoadSet(TIMER0_BASE,TIMER_A,0xFFFF);
MAP_TimerPrescaleSet(TIMER0_BASE,TIMER_A,0xFF);
MAP_TimerIntDisable(TIMER0_BASE,TIMER_A);
MAP_TimerEnable(TIMER0_BASE, TIMER_A);
}

void PP3_ISR()

{

MAP_GPIOIntClear(GPIO_PORTP_BASE, GPIO_INT_PIN_3);
EdgD = MAP_GPIOPinRead(GPIO_PORTP_BASE, GPIO_PIN_3);
switch (EdgD)
{
        case 8:    //Rising edge
        PR = (MAP_TimerValueGet(TIMER0_BASE, TIMER_A)) +(MAP_TimerPrescaleGet(TIMER0_BASE, TIMER_A) << 16);
        break;

        case 0:     // Falling Edge
        PF = (MAP_TimerValueGet(TIMER0_BASE, TIMER_A))+ (MAP_TimerPrescaleGet(TIMER0_BASE, TIMER_A) << 16);
        if(PF> PR)
        {
          PLSWArry[Pc++]=((PF-PR)/120); // clock = 120
        }
        else
             PLSWArry[Pc++]= ((PF + 16777215) - PR)/120; //clock =120

        break;
}
}

Regards,

Sumit 

Hi,

Please refer the example I provided at C:\ti\TivaWare_C_Series-2.2.0.295\examples\boards\ek-tm4c1294xl\timer_edge_capture. If you want to measure the an input pin then you should configure the timer in ' Input Edge Time Capture' mode as in TIMER_CFG_A_CAP_TIME_UP. Refer to Input Edge-Time mode in the datasheet. 

Since you are not measuring a  long pulse, you can just use either Timer_A or Timer_B in 24bit resolution. You can configure the capture event to be both edges so it will measure both the high and low phases of the input. 

Hi, Charles.

      Actually Timer capture and compare mode is not available for PP3, and in our hardware it is connected to PP3 for both edge.

 init_PP3_ISR()

{

MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOP);
while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOP))
{

}
MAP_GPIOPinTypeGPIOInput(GPIO_PORTP_BASE, GPIO_PIN_3);
MAP_GPIODMATriggerEnable(GPIO_PORTP_BASE, GPIO_PIN_3);
MAP_GPIOIntTypeSet(GPIO_PORTP_BASE, GPIO_PIN_3, GPIO_BOTH_EDGES); // GPIO_RISING_EDGE and falling edge
MAP_GPIOIntEnable(GPIO_PORTP_BASE, GPIO_INT_PIN_3);

}

gpioPulse_hwi = Hwi_create(INT_GPIOP3_TM4C129, Pulse_Detect_ISR, &gpioPulse_hwiParams, &eb_HiPulse); // hardware interrupt enable
if( gpioPulse_hwi == NULL)
{
System_abort(" *** Hardware interrupt create fail for pulse monitor");
}

Hwi_enableInterrupt(INT_GPIOP3_TM4C129);   

So, Is there any other way to solve with this hardware(PP3)? 

Thanks and Regards,

Sumit Chaulya

Hi,

  There is an issue to your approach. If the next edge comes too quick you may just miss it using one timer. Think about that you get a PP3 interrupt for a rise edge. It takes some time/cycles for the processor to respond to it and jumps to the ISR. In your ISR, you are clearing the PP3 interrupt flag. What if the next falling edge comes quickly around the same time you are clear the flag? Since you just clear the flag, you lose the falling edge event. In the next rise edge interrupt, you will be measuring the period instead of duty cycle. The solution is to use two timers on two different pins with one generating an interrupt for rise edge and the other generating interrupt on fall edge. This is how the example was developed to address capturing short pulses. 

Hi, Charles.

      My pulse measurement is working fine with TIMER0_BASE, TIMER_A.

      But  if  use TIMER0_BASE,TIMER_B i am not getting correct value.

      Am i doing something wrong ??

void timer_config(void)
{
MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);

while(!MAP_SysCtlPeripheralReady(SYSCTL_PERIPH_TIMER0))
{

}
MAP_TimerClockSourceSet(TIMER0_BASE, TIMER_CLOCK_SYSTEM);
MAP_TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC_UP);
MAP_TimerLoadSet(TIMER0_BASE,TIMER_B,0xFFFF); 
MAP_TimerPrescaleSet(TIMER0_BASE,TIMER_B,0xFF);
MAP_TimerIntDisable(TIMER0_BASE,TIMER_B);
MAP_TimerDisable(TIMER0_BASE, TIMER_B);
}

//measurement 

void measure_func()

{

MAP_GPIOIntClear(GPIO_PORTP_BASE, GPIO_INT_PIN_3);
EdgD = MAP_GPIOPinRead(GPIO_PORTP_BASE, GPIO_PIN_3);
switch (EdgD)
{
case 8: // Rising edge
PR = (MAP_TimerValueGet(TIMER0_BASE, TIMER_B)) +(MAP_TimerPrescaleGet(TIMER0_BASE, TIMER_B) << 16);
break;

case 0: // falling edge
PF = (MAP_TimerValueGet(TIMER0_BASE, TIMER_B))+ (MAP_TimerPrescaleGet(TIMER0_BASE, TIMER_B) << 16);
Swi_post(Pulse_Detect_Swi); // call Pulse_Detect_Swi_func
break;
}

}

Regards,

Sumit 

Hi,

SUMIT CHAULYA said:

MAP_TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC_UP);

This line is wrong if you want to use Timer-B. When you use TIMER_CFG_PERIODIC_UP, this is to use the full-width timer, meaning to combine Timer_A and Timer_B as one 32-bit timer.

You should use as follows if you want to use just timer_B. 

TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_B_PERIODIC_UP);