Using Beagle Board xM GPIO as input

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Hi everyone

I am working on a ultrasound imaging project which involves using the Beagle Board SPI interface to communicate with another board.

I am planning to use the GPIO pin(24) at the expansion connector as input to monitor the interrupt signal from another board. I read the DM37x TRM and followed those steps closely, but it did not work out as expected.

This is my program which is based on the example program i found herehttp://41j.com/blog/2011/09/beagleboard-gpio-input-driverless/

#include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/mman.h>

int main(void)
 {
  printf ("open file descriptor for PADCONFIG\n");
  int fd = open("/dev/mem", O_RDWR | O_SYNC); //O_SYNC makes the memory uncacheable
  if (fd < 0) {
    printf("Could not open PADCONFIG memory fd\n");
  return 0;
 }

// Pad configuration
printf ("map PINCONFIG\n");
volatile ulong *pinconf;
pinconf = (ulong*) mmap(NULL, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED, fd,              0x48000000);
if (pinconf == MAP_FAILED) {
    printf("Pinconf Mapping failed\n");
    close(fd);
return 0;
}
printf ("set pinconfig GPIO\n");

    pinconf[0x21BC/4] = 0x011C011C;//mux gpio168 as input
    close(fd);
   /* -------------------------------------- */

printf ("open file descriptor for GPIO\n");
int gpio_fd = open("/dev/mem", O_RDWR | O_SYNC);
if (gpio_fd < 0) {
    printf("Could not open GPIO memory fd\n");
return 0;
}

// GPIO configuratio
printf ("map GPIO\n");
volatile ulong *gpio;
gpio = (ulong*) mmap(NULL, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED,                                                                                                                                                         g       gpio_fd, 0x49050000);
if (gpio == MAP_FAILED) {
    printf ("GPIO Mapping failed\n");
    close(gpio_fd);
    return 0;
}
printf ("set GPIO config\n");
    // Configure GPIO pin on bank 6 as output.
gpio[0x8034/4] |=0x00000100; //set gpio168 in bank 6 as input
gpio[0x8080/4] = 0x00000100;  //clear the wake-up enable in GPIO_WAKEUPENABLE page 3520
gpio[0x8060/4] = 0x00000100; // clear the the corresponding bit in the                         
gpio[0x8070/4] = 0x00000100;//0x1: Clear the corresponding bit in the GPIO_IRQENABLE2 register page 351
if(gpio[0x8038/4]&&0x00000100)
    printf("The out put is 1\n");//not sure about this part
  else
    printf("The out put is 0\n");

close(gpio_fd);
 }

`

`

I am having the problem when the program runs here.(set the corresponding bit in the GPIO_OE reg)

gpio[0x8034/4] |=0x00000100; //set gpio168(pin24) in bank 6 as input

`

`

I am very new to bit wise operation and not sure if i am doing it right.

Also, I want to check the level of my input by check the data in GPIO_DATAIN registor(0x8038) It is legal to do something like this to check that bit?

for(;;){ 
   if(gpio[0x8038/4]&&0x00000100)
      printf("The input is 1\n");//not sure about this part
    else
      printf("The input is 0\n");
      }

`

`

The way they do it in the example program is like:

  for(;;) {
  if(gpio[0x6038/4] == 201390076) printf("1\n");
  // printf("gpio5: %d \n",gpio[0x6038/4]);
    }

I have no idea how they got this 201390076 number.

Please advise, thanks.