TMS320F28335: TMS320F28335 Gpio speed

"The maximum toggling frequency of the GPIO pin is 20 MHz for the F281x devices and
25 MHz for the F280x/F28xxx devices." (from SPRAAS1C "Hardware Design Guide)

Thanks for the reply Todd.

I am facing an issue, that whenever my input signal (square wave of 100 kHz) at GPIO pin( which i have configured as XINT1) makes transition from low to high, why my GPIO pin (which i have configured as an output ) is taking 250 ns to make transition from low to high.

I wonder if that has to do with the interrupt service routine - there is some latency involved before getting to the first line of an interrupt service routine. You may be seeing something related to that. Have you seen the write-up on interrupts in the F28335 of C2000 Archived Workshops? processors.wiki.ti.com/.../C2000_Archived_Workshops -> F28335 -> Student Guide -> Chapter 4 (Interrupts) [as I remember...]

Hello Todd, 

I read the interrupt part of the archived workshop. I found that external interrupt takes a minimum of 16 cycles (100ns) before going into the ISR. That may explain one part of the delay. I suppose the other part of the delay is because of the involved wait states. 

Thanks for your help Todd.

Regards

Nikhil

Nikhil,

Can you describe your desired system behavior? There may be other approaches depending on your end goal.

-Tommy

Hi Tommy,

I am using an external interrupt (frequency of 100 kHz) to toggle the state of a GPIO30 ( configured as an output pin).

This is my code:

//GPIO30 as an output 

GpioCtrlRegs.GPAMUX2.bit.GPIO30 = 0; //GPIO30
GpioCtrlRegs.GPADIR.bit.GPIO30 = 1; //Output

//GPIO21 as an input

GpioCtrlRegs.GPAMUX2.bit.GPIO21 = 0; // GPIO
GpioCtrlRegs.GPADIR.bit.GPIO21 = 0; // input
GpioCtrlRegs.GPAQSEL2.bit.GPIO21 = 0; // Xint1 Synch to SYSCLKOUT only

//GPIO21 is XINT1

GpioIntRegs.GPIOXINT1SEL.bit.GPIOSEL = 0x0015; // Xint1 is GPIO0
XIntruptRegs.XINT1CR.bit.POLARITY = 01; // XINT1 Polarity configuration
XIntruptRegs.XINT1CR.bit.ENABLE = 1; //enable Xint1

 EDIS;

interrupt void xint1_isr(void)
{
counterxint++ ;

GpioDataRegs.GPATOGGLE.bit.GPIO30=1;

PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;

EINT;

}

The blue curve represents the external interrupt and yellow curve represents output of my GPIO30. I wanted to reduce the time gap between them as low as possible.

Nikhil,

Do you think that the EPWM would work for you? The EPWM hardware trip response latency should be quicker than an XINT+software response.

-Tommy

No. EPWM wont work, because i have to use an external signal (my sense signal from a control board) to generate an interrupt.

Regards
Nikhil