init

gpio-raw.c

@@ -0,0 +1,56 @@
+#include "gpio-raw.h"
+
+int  mem_fd;
+char *gpio_mem, *gpio_map;
+char *spi0_mem, *spi0_map;
+
+
+// I/O access
+volatile unsigned *gpio;
+
+//
+// Set up a memory regions to access GPIO
+//
+bool setup_io()
+{
+   /* open /dev/mem */
+   if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
+      /*printf("can't open /dev/mem \n");
+      exit (-1);*/
+     return false;
+   }
+
+   /* mmap GPIO */
+
+   // Allocate MAP block
+   if ((gpio_mem = (char*)malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
+      /*printf("allocation error \n");
+      exit (-1);*/
+     return false;
+   }
+
+   // Make sure pointer is on 4K boundary
+   if ((unsigned long)gpio_mem % PAGE_SIZE)
+     gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
+
+   // Now map it
+   gpio_map = (char *)mmap(
+      (caddr_t)gpio_mem,
+      BLOCK_SIZE,
+      PROT_READ|PROT_WRITE,
+      MAP_SHARED|MAP_FIXED,
+      mem_fd,
+      GPIO_BASE
+   );
+
+   if ((long)gpio_map < 0) {
+      /*printf("mmap error %d\n", (int)gpio_map);
+      exit (-1);*/
+     return false;
+   }
+
+   // Always use volatile pointer!
+   gpio = (volatile unsigned *)gpio_map;
+  return true;
+
+} // setup_io

gpio-raw.h

@@ -0,0 +1,39 @@
+#ifndef GPIO_RAW_H
+#define GPIO_RAW_H
+#define BCM2708_PERI_BASE        0x20000000
+#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+
+#include <unistd.h>
+
+#define PAGE_SIZE (4*1024)
+#define BLOCK_SIZE (4*1024)
+
+extern int  mem_fd;
+extern char *gpio_mem, *gpio_map;
+extern char *spi0_mem, *spi0_map;
+
+
+// I/O access
+extern volatile unsigned *gpio;
+
+// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
+#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
+#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
+#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
+
+#define GPIO_SET *(gpio+7)  // sets   bits which are 1 ignores bits which are 0
+#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
+#define GPIO_LEV *(gpio+13)
+#define GPIO_VALUE(PIN) ((GPIO_LEV & (1 << PIN)) != 0)
+
+bool setup_io();
+
+#endif // GPIO_RAW_H

main.c

@@ -0,0 +1,58 @@
+#define _POSIX_C_SOURCE 199309L
+#include <sys/time.h>
+#include <time.h>
+#include <iostream>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+
+#include "gpio-raw.h"
+
+bool thread_exit = false;
+
+static void signal_handler(int signo)
+{
+    thread_exit = true;
+}
+
+void* worker(void*)
+{
+  FILE* fd = fopen("clock.out", "w");
+  while (!thread_exit)
+    sleep(1);
+  fclose(fd);
+  return 0;
+}
+
+int main(int argc, char* argv[])
+{
+  signal(SIGINT, signal_handler);
+  setup_io();
+  INP_GPIO(4); // must use INP_GPIO before we can use OUT_GPIO
+
+  struct timeval t1, t2;
+  const int n = argc == 2 ? atoi(argv[1]) : 1000000;
+  pthread_t thread;
+  pthread_create(&thread, 0, worker, 0);
+
+  gettimeofday(&t1, NULL);
+  for (int i = 0; !thread_exit; ++i)
+  {
+    //GPIO_VALUE(6);
+    //tab[i] = GPIO_VALUE(6);
+    printf("%i\n", GPIO_VALUE(6));
+    //fprintf(fd, "%i\n", v);
+    //GPIO_SET = 1<<4;
+    //GPIO_CLR = 1<<4;
+  }
+  gettimeofday(&t2, NULL);
+  pthread_join(thread, 0);
+  unsigned long long ut1 = (__suseconds_t)(1000000L * t1.tv_sec + t1.tv_usec);
+  unsigned long long ut2 = (__suseconds_t)(1000000L * t2.tv_sec + t2.tv_usec);
+  std::cout << ut1 << " " << ut2 << " ";
+  std::cout << (ut2 - ut1) << " " << (float)(ut2 - ut1) / n << std::endl;
+  return 0;
+}