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Explain statements in the program blinking leds

NeihtGnod
Prodigy 65 points


Hi all

You to explain his statements in the program blinking leds

#include "lm4f120h5qr.h"

void main(void)
{
long i;
SYSCTL_RCGC2_R = SYSCTL_RCGC2_GPIOF;
GPIO_PORTF_DEN_R = 0x08+0x04+0x02;
GPIO_PORTF_DIR_R = 0x08+0x04+0x02;
while(1)
{
GPIO_PORTF_DATA_R=0x02;
for(i=0;i<3000000;i++);
GPIO_PORTF_DATA_R=0x00;
for(i=0;i<5000000;i++);
}
}

Because his new learn lm4f120 should difficult to understand, hope you to explain the above statement 

Thank :)

  • 0
    Guru 47900 points

    Suspect you question:

    a) GPIO_PORTF_DEN_R = 0x08+0x04+0x02;   enables bits 3, 2, and 1 PortF.   Better to use |= to avoid "disturbance" to other bits

    b) GPIO_PORTF_DIR_R = 0x08+0x04+0x02;   configures same bits as above as outputs.  Again better to use |=

    c) the while loop seems bit strange - again "heavy handed" use of = sets only bit 1, delays, then 2nd "heavy handing" resets all bits.  (&= better)

    Doubt that the single #include you list is adequate for this piece of code to run.  Further review of the original code will assist...