--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/kstmApp/src/pi_2_mmio.c	Fri Aug 14 11:30:43 2015 +0200
@@ -0,0 +1,71 @@
+// Copyright (c) 2014 Adafruit Industries
+// Author: Tony DiCola
+// Based on code from Gert van Loo & Dom: http://elinux.org/RPi_Low-level_peripherals#GPIO_Code_examples
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "pi_2_mmio.h"
+
+#define GPIO_BASE_OFFSET 0x200000
+#define GPIO_LENGTH 4096
+
+volatile uint32_t* pi_2_mmio_gpio = NULL;
+
+int pi_2_mmio_init(void) {
+  if (pi_2_mmio_gpio == NULL) {
+    // Check for GPIO and peripheral addresses from device tree.
+    // Adapted from code in the RPi.GPIO library at:
+    //   http://sourceforge.net/p/raspberry-gpio-python/
+    FILE *fp = fopen("/proc/device-tree/soc/ranges", "rb");
+    if (fp == NULL) {
+      return MMIO_ERROR_OFFSET;
+    }
+    fseek(fp, 4, SEEK_SET);
+    unsigned char buf[4];
+    if (fread(buf, 1, sizeof(buf), fp) != sizeof(buf)) {
+      return MMIO_ERROR_OFFSET;
+    }
+    uint32_t peri_base = buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3] << 0;
+    uint32_t gpio_base = peri_base + GPIO_BASE_OFFSET;
+    fclose(fp);
+
+    int fd = open("/dev/mem", O_RDWR | O_SYNC);
+    if (fd == -1) {
+      // Error opening /dev/mem.  Probably not running as root.
+      return MMIO_ERROR_DEVMEM;
+    }
+    // Map GPIO memory to location in process space.
+    pi_2_mmio_gpio = (uint32_t*)mmap(NULL, GPIO_LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, fd, gpio_base);
+    close(fd);
+    if (pi_2_mmio_gpio == MAP_FAILED) {
+      // Don't save the result if the memory mapping failed.
+      pi_2_mmio_gpio = NULL;
+      return MMIO_ERROR_MMAP;
+    }
+  }
+  return MMIO_SUCCESS;
+}