Added a Makefile to make building less ambiguous.

Added an example program to demonstrate library usage.
Added additional information to the README to provide instructions on building and usage.

Makefile

@@ -0,0 +1,30 @@
+CC=gcc
+CFLAGS=-fPIC
+CFLAGS_SHARED=-shared
+OBJ=mma8451.o
+LIBNAME=libmma8451.so
+TESTOBJ=mma8451-test.o
+TESTNAME=mma8451-test
+
+all: compile
+
+compile: $(LIBNAME) $(TESTNAME)
+
+install: $(LIBNAME)
+	cp $(LIBNAME) /usr/lib/$(LIBNAME)
+	cp $(TESTNAME) /usr/bin/$(TESTNAME)
+
+fix-i2c:
+	echo -n 1 > /sys/module/i2c_bcm2708/parameters/combined
+
+clean:
+	rm -f $(OBJ) $(TESTOBJ) $(LIBNAME) $(TESTNAME)
+
+%.o: %.c
+	$(CC) -c -o $@ $< $(CFLAGS)
+
+$(LIBNAME): $(OBJ)
+	gcc -o $@ $^ $(CFLAGS) $(CFLAGS_SHARED)
+
+$(TESTNAME): $(LIBNAME) $(TESTOBJ)
+	gcc -o $@ $^ $(CFLAGS) -L. -lmma8451

README.md

@@ -1,2 +1,28 @@
 # libmma8451
-A small C library for interacting with a MMA8451 accelerometer using libi2c.
+A small C library for interacting with a [MMA8451 accelerometer](https://www.adafruit.com/product/2019)
+using libi2c.
+
+Built from the [reference documentation](https://www.nxp.com/docs/en/data-sheet/MMA8451Q.pdf)
+provided by NXP.
+
+The software was built originally for use with the Raspberry Pi but should work with
+any Linux system with the I2C kernel module and libi2c installed. The library supports working
+with multiple accelerometers at once.
+
+To build and install the library and test application:
+
+    $ make
+    $ sudo make install
+
+To run the test application:
+
+    $ mma8451-test /dev/i2c-1 0x1c
+    Attempting to open /dev/i2c-1 and talk to I2C device at 0x1c
+    Successfully opened device, initializing...
+    Successfully initialized, starting capture. (Press Ctrl-C to stop)
+    x=-0.612916, y=-9.040505, z=3.524265, samplesPerSecond=1477.832512
+
+On older versions of Raspbian the i2c_bcm2708 kernel module needed to be set to combined mode.
+This can be done by doing the following:
+
+    $ sudo sh -c "echo -n 1 > /sys/module/i2c_bcm2708/parameters/combined"

mma8451-test.c

@@ -0,0 +1,136 @@
+/*
+ * libmma8451 - Library for controlling and reading from MMA8451 accelerometers.
+ * Copyright (C) 2017  Michael Powers
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+/*
+ * This is a simple example of how to open and read from an
+ * accelerometer using the libmma8451 library.
+ */
+#include "mma8451.h"
+#include <stdio.h>
+#include <time.h>
+
+/**
+ * Prints the usage statement for this application.
+ */
+void printUsage() {
+    printf("Usage: mma8451-test [device path] [i2c address]\n");
+    printf("  e.g. mma8451 /dev/i2c-1 0x1c\n\n");
+}
+
+/**
+ * Initializes the accelerometer and gets it ready to capture.
+ * @param dev Device to initialize.
+ * @return 1 on success, 0 on failure.
+ */
+int initializeDevice(mma8451* dev) {
+    //Reset the device back to defaults.
+	mma8451_reset(dev);
+
+    //Wait one second, it takes the device a short amount of time
+    //to come back.
+    sleep(1);
+
+    //Set the bit width of the acceleration values.
+    if(!mma8451_set_output_size(dev, MMA8451_8BIT_OUTPUT)) return 0;
+    //Set the noise mode.
+    if(!mma8451_set_low_noise(dev, 1)) return 0;
+    //Set the power mode.
+    if(!mma8451_set_power_mode(dev, MMA8451_POWER_MODE_HIGH_RES)) return 0;
+    //Turn on orientation detection.
+    if(!mma8451_set_orientation_detection(dev, 1)) return 0;
+    //Set the accuracy range.
+    if(!mma8451_set_range(dev, MMA8451_RANGE_2G)) return 0;
+    //Enable interrupts.
+    if(!mma8451_set_interrupt_enable(dev, 1)) return 0;
+    //Set interrupts for pin1 on the accelerometer.
+    if(!mma8451_set_interrupt_pin1(dev, 1)) return 0;
+    //Start capturing.
+    if(!mma8451_set_active(dev, 1)) return 0;
+
+    return 1;
+}
+
+/**
+ * Main function, starts the program and attempts to open the accelerometer
+ * and read from it.
+ */
+int main(int argc, char** argv) {
+    struct timespec start;
+    struct timespec sample;
+    unsigned int samples = 0;
+    char* path;
+    unsigned char address;
+
+    //Make sure we have the right number of command line arguments.
+    if(argc != 3) {
+        printUsage();
+        return -1;
+    }
+
+    //Parse the arguments.
+    path = argv[1];
+    address = (unsigned char)strtol(argv[2], NULL, 0);
+
+    printf("Attempting to open %s and talk to I2C device at 0x%02x\n", path, address);
+    mma8451* dev = mma8451_open(path, address);
+    if(dev == NULL) {
+        perror("Unable to open device.");
+        return -1;
+    }
+
+    printf("Successfully opened device, initializing...\n");
+    if(!initializeDevice(dev)) {
+        perror("Unable to initialize device.");
+        return -2;
+    }
+
+    printf("Successfully initialized, starting capture. (Press Ctrl-C to stop)\n");
+    clock_gettime(CLOCK_REALTIME, &start);
+
+    printf("\n");
+    while(1) {
+        mma8451_acceleration data;
+        long long duration;
+        double samplesPerSecond;
+
+        //Actually read the acceleration data from the accelerometer.
+        if(!mma8451_get_acceleration(dev, &data)) {
+            return 0;
+        }
+
+        clock_gettime(CLOCK_REALTIME, &sample);
+        samples++;
+
+        //Calculate the samples per second.
+        duration = ((sample.tv_sec - start.tv_sec) * 1000);
+        duration += (sample.tv_nsec - start.tv_nsec) / 1.0e6;
+        samplesPerSecond = (duration > 0) ? samples / ((double)duration / 1000) : 0;
+
+        //Every 100th sample, print a message showing the latest measurements.
+        if(samples % 100 == 0) {
+            //Move up a line and clear to the beginning of the line.
+            printf("%c[1A%c[K", 0x1b, 0x1b);
+            //Print the sample.
+            printf("x=%f, y=%f, z=%f, samplesPerSecond=%f\n", data.x, data.y, data.z, samplesPerSecond);
+        }
+    }
+
+    mma8451_close(dev);
+    return 0;
+}