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io.c
// filename button.c
// connect a button to DIO pin 1 and ground
// blinks green and red led on the ts-7200 when button is pressed
//
// compile arm-linux-gcc -o button button.c
//

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

int main(int argc, char **argv)
{
   volatile unsigned int *PEDR, *PEDDR, *PBDR, *PBDDR, *GPIOBDB;
   int i;
   unsigned char state;
   unsigned char *start;
   int fd = open("/dev/mem", O_RDWR|O_SYNC);

   start = mmap(0, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x80840000);
   PBDR = (unsigned int *)(start + 0x04);     // port b
   PBDDR = (unsigned int *)(start + 0x14);    // port b direction register
   PEDR = (unsigned int *)(start + 0x20);     // port e data
   PEDDR = (unsigned int *)(start + 0x24);    // port e direction register
   GPIOBDB = (unsigned int *)(start + 0xC4);  // debounce on port b

   *PBDDR = 0xf0;                   // upper nibble output, lower nibble input
   *PEDDR = 0xff;                             // all output (just 2 bits)
   *GPIOBDB = 0x01;                       // enable debounce on bit 0

   state = *PBDR;                             // read initial state
   while (state & 0x01) {                     // wait until button goes low
      state = *PBDR;                          // remember bit 0 is pulled up with 4.7k ohm
   }


   // blink 5 times, sleep 1 second so it's visible
   for (i = 0; i < 5; i++) {
      *PEDR = 0xff;
      sleep(1);
      *PEDR = 0x00;
      sleep(1);
   }
   close(fd);
   return 0;
}

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