TM4C123GH6PZ: Generate a precise pulse with minimum Duration

Hi,

I am using 8MHz external crystal as clock source. So in such case what will be the minimum pulse duration I can achieve. Only direct port toggling is enough for generating a pulse. 

Thank you,

Alphy

Hi,

I used 80 MHz PLL as the clock source and I am getting signal having following features,

Period 1.6 us
Rise time = 44 ns
Fall time = 52 to 60 ns
 On time = 728 ns
Off time = 872 ns

I want signal of 1us But not able to get signal while using API functions.

The given below is the program,

int main()
{
SysCtlClockSet(SYSCTL_SYSDIV_1|SYSCTL_USE_PLL |SYSCTL_XTAL_8MHZ|SYSCTL_OSC_MAIN);//80MHz crystall oscilator
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_7);
	
  while(1)
  {
   GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_7,GPIO_PIN_7); //No delay

    GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_7,0);
  }

}

I tried to with direct memory write and signal features are,

Period 1.4 us
Rise time = 48 ns to 43
Fall time = 67 to 60
 On time = 574 ns
Off time = 868 ns

code given below.

int main()
{
SysCtlClockSet(SYSCTL_SYSDIV_1|SYSCTL_USE_PLL |SYSCTL_XTAL_8MHZ|SYSCTL_OSC_MAIN);//80MHz crystall oscilator
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_7);
	
	while(1)
	{
	 // GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_7,GPIO_PIN_7);
		 GPIO_PORTA_DATA_R |= 0x80;  //Data write
	
	  GPIO_PORTA_DATA_R &= ~(0x80);  // Turn off the LED.
        }
}

Please let me know is there any other way to reduce this time to 1us range.or is any way to write the pin high and low by writing directly to the respective register.

Thank you,

Alphy

Hello Alphy,

For one, that is about as fast as you can make it go.

Also, I didn't even think about accounting for the response time in terms of signal rising, so sorry for that.

But I am not following regarding the issue now. You wanted a 'single pulse' shorter than 1 us, but I see these stats:

Rise time = 48 ns to 43
Fall time = 67 to 60
 On time = 574 ns

That adds up to be shorter than 1 us for a single pulse. If you want a continuous pulse, that is an entirely different topic...