diff --git a/Makefile b/Makefile
index 9514ba9..1932f3c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,8 @@
 CC=gcc
-CFLAGS=-O2 -std=c89 -W -Werror -Wall -Wextra -pedantic -I. 
+CFLAGS=-O0 -g3 -ggdb -std=c89 -W -Werror -Wall -Wextra -Wpedantic -pedantic-errors -Wformat-signedness -I.
+CFLAGS+=-Wlogical-op -Wmissing-declarations -Wswitch-default -Wundef -Wformat=2
 LFLAGS=-lm
-CFILES=$(wildcard ./*.c)
+CFILES=$(wildcard *.c)
 all:
 	$(CC) $(CFLAGS) $(CFILES) -o lis3dh $(LFLAGS)
 
diff --git a/README.md b/README.md
index 4128a20..f7b3e78 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,8 @@ int deinit(void);
 ```
 All above functions return `0` on success.
 
+The `init` and `deinit` pointers can both be set to `NULL` and they won't be run.
+
 ## Usage
 Simple example:
 ```c
@@ -146,6 +148,7 @@ x: 0.518000, y: -0.846000, z: -0.100000
 Instead of polling for every single [x y z] set, a FIFO with programmable capacity ("watermark") can be used like such:
 
 All FIFO readings use 10-bit resolution regardless of the mode set in `lis.cfg.mode`.
+
 The watermark level can also be adjusted to a value [0-31] inclusive by modifying the `lis.cfg.fifo.fth` property before calling configure().
 ```c
 #define _GNU_SOURCE
diff --git a/lis3dh.c b/lis3dh.c
index 5b21aba..45b2c4e 100644
--- a/lis3dh.c
+++ b/lis3dh.c
@@ -1,3 +1,5 @@
+#include <stddef.h>
+#include <string.h>
 #include "lis3dh.h"
 #include "registers.h"
 
@@ -38,8 +40,11 @@ int lis3dh_init(lis3dh_t *lis3dh) {
     uint8_t result;
     int err = 0;
 
-    if (lis3dh->dev.init() != 0) {
-        return 1;
+    /* if init has been given, check it */
+    if (lis3dh->dev.init != NULL) {
+        if (lis3dh->dev.init() != 0) {
+            return 1;
+        }
     }
 
     err |= lis3dh->dev.read(REG_WHO_AM_I, &result, 1);
@@ -97,10 +102,10 @@ int lis3dh_configure(lis3dh_t *lis3dh) {
     int err = 0;
 
     /* the 0x07 enables Z, Y and X axis in that order */
-    ctrl_reg1 = 0 | (lis3dh->cfg.rate << 4) | 0x07;
+    ctrl_reg1 = (lis3dh->cfg.rate << 4) | 0x07;
     ctrl_reg2 = 0;
     ctrl_reg3 = 0;
-    ctrl_reg4 = 0 | (lis3dh->cfg.range << 4);
+    ctrl_reg4 = (lis3dh->cfg.range << 4);
     ctrl_reg5 = 0;
     ctrl_reg6 = 0;
     fifo_ctrl_reg = 0;
@@ -204,77 +209,36 @@ int lis3dh_poll_fifo(lis3dh_t *lis3dh) {
 /* the real size of the int you get back from reading the acc u16 
    depends on the power mode. 
    shift down the 16 bit word by this amount: */
-static uint8_t acc_shift(lis3dh_t *lis3dh) {
-    switch (lis3dh->cfg.mode) {
-        case LIS3DH_MODE_HR:
-            return 4; /* i12 */
-        case LIS3DH_MODE_NORMAL:
-            return 6; /* i10 */
-        case LIS3DH_MODE_LP:
-            return 8; /* i8 */
+static uint8_t acc_shift(uint8_t mode) {
+    switch (mode) {
+        case LIS3DH_MODE_HR:     return 4;  /* i12 */
+        case LIS3DH_MODE_NORMAL: return 6;  /* i10 */
+        case LIS3DH_MODE_LP:     return 8;  /* i8 */
+        default:                 return 0;
     }
-
-    return 0;
 }
 
 /* returns a scalar that when multiplied with axis reading
    turns it to a multiple of mg. */
-static uint8_t acc_sensitivity(lis3dh_t *lis3dh) {
-    uint8_t mode = lis3dh->cfg.mode;
-
-    switch (lis3dh->cfg.range) {
-        case LIS3DH_FS_2G:
-            if (mode == LIS3DH_MODE_LP) {
-                return 16;
-            } else if (mode == LIS3DH_MODE_NORMAL) {
-                return 4;
-            } else {
-                return 1;
-            }
-            break;
-
-        case LIS3DH_FS_4G:
-            if (mode == LIS3DH_MODE_LP) {
-                return 32;
-            } else if (mode == LIS3DH_MODE_NORMAL) {
-                return 8;
-            } else {
-                return 2;
-            }
-            break;
-
-        case LIS3DH_FS_8G:
-            if (mode == LIS3DH_MODE_LP) {
-                return 64;
-            } else if (mode == LIS3DH_MODE_NORMAL) {
-                return 16;
-            } else {
-                return 4;
-            }
-            break;
-
-        case LIS3DH_FS_16G:
-            if (mode == LIS3DH_MODE_LP) {
-                return 192;
-            } else if (mode == LIS3DH_MODE_NORMAL) {
-                return 48;
-            } else {
-                return 12;
-            }
-            break;
+static uint8_t acc_sensitivity(uint8_t mode, uint8_t range) {
+    switch (range) {
+        case LIS3DH_FS_2G:    return (mode == LIS3DH_MODE_LP) ? 16  : (mode == LIS3DH_MODE_NORMAL) ? 4  : 1;
+        case LIS3DH_FS_4G:    return (mode == LIS3DH_MODE_LP) ? 32  : (mode == LIS3DH_MODE_NORMAL) ? 8  : 2;
+        case LIS3DH_FS_8G:    return (mode == LIS3DH_MODE_LP) ? 64  : (mode == LIS3DH_MODE_NORMAL) ? 16 : 4;
+        case LIS3DH_FS_16G:   return (mode == LIS3DH_MODE_LP) ? 192 : (mode == LIS3DH_MODE_NORMAL) ? 48 : 12;
+        default:              return 0;
     }
-
-    return 0;
 }
 
+
 int lis3dh_read(lis3dh_t *lis3dh) {
     uint8_t data[6];
     int32_t x, y, z;
     uint8_t scale, sens;
     int err = 0;
 
-    scale = acc_shift(lis3dh);
-    sens = acc_sensitivity(lis3dh);
+    scale = acc_shift(lis3dh->cfg.mode);
+    sens = acc_sensitivity(lis3dh->cfg.mode, lis3dh->cfg.range);
 
     /* must set MSbit of the address to multi-read and 
        have the device auto-increment the address. */
@@ -301,17 +265,7 @@ int lis3dh_read_fifo(lis3dh_t *lis3dh, struct lis3dh_fifo_data *fifo) {
 
     /* FIFO is always 10-bit */
     scale = 6;
-
-    /* normal mode */
-    if (lis3dh->cfg.range == LIS3DH_FS_2G) {
-        sens = 4;
-    } else if (lis3dh->cfg.range == LIS3DH_FS_4G) {
-        sens = 8;
-    } else if (lis3dh->cfg.range == LIS3DH_FS_8G) {
-        sens = 16;
-    } else { /* 16G */
-        sens = 48;
-    }
+    sens = acc_sensitivity(lis3dh->cfg.mode, lis3dh->cfg.range);
 
     /* fifo buffer is max 32 */
     fifo->size = lis3dh->cfg.fifo.fth > 32 ? 32 : lis3dh->cfg.fifo.fth;
@@ -334,8 +288,13 @@ int lis3dh_read_fifo(lis3dh_t *lis3dh, struct lis3dh_fifo_data *fifo) {
     return err;
 }
 
+/* if NULL, this function doesn't have to be called */
 int lis3dh_deinit(lis3dh_t *lis3dh) {
-    return lis3dh->dev.deinit();
+    if (lis3dh->dev.deinit != NULL) {
+        return lis3dh->dev.deinit();
+    }
+
+    return 0;
 }
 
 /* read INT1_SRC to clear latched INT1 irq */
diff --git a/main.c b/main.c
index 6c005d0..88b08cd 100644
--- a/main.c
+++ b/main.c
@@ -10,12 +10,12 @@
 #define GPIO_INTERRUPT_PIN 12
 
 /* calc magnitude of accel [x y z] vector */
-float mag(float x, float y, float z) {
+static float mag(float x, float y, float z) {
     return sqrt( powf(x, 2) + powf(y, 2) + powf(z, 2) );
 }
 
 /* print message then exit */
-void quit(const char *msg, lis3dh_t *lis) {
+static void quit(const char *msg, lis3dh_t *lis) {
     lis->dev.deinit();
     fprintf(stderr, "%s\n", msg);
     exit(1);
@@ -25,7 +25,7 @@ int main() {
 
     lis3dh_t lis;
     struct lis3dh_fifo_data fifo;
-    int k;
+    int i, k;
 
     /* set fn ptrs to rw on bus (i2c or SPI) */
     lis.dev.init = i2c_init;
@@ -53,6 +53,8 @@ int main() {
     lis.cfg.fifo.trig = LIS3DH_FIFO_TRIG_INT1;
     lis.cfg.int1.wtm = 1;
     lis.cfg.int1.latch = 1;
+    lis.cfg.filter.mode = LIS3DH_FILTER_MODE_REFERENCE;
+    lis.cfg.filter.cutoff = LIS3DH_FILTER_CUTOFF_8;
     
 
     /* write device config */
@@ -60,24 +62,28 @@ int main() {
         quit("configure()", &lis);
     }
     
-    /* wait for interrupt from LIS3DH */
-    if (int_poll(GPIO_INTERRUPT_PIN)) {
-        quit("int_poll()", &lis);
-    }
+    for(i=0; i<50; i++) {
+            /* wait for interrupt from LIS3DH */
+        if (int_poll(GPIO_INTERRUPT_PIN)) {
+            quit("int_poll()", &lis);
+        }
 
-    if (lis3dh_clear_int1(&lis)) {
-        quit("clear_int1()", &lis);
-    }
+        if (lis3dh_clear_int1(&lis)) {
+            quit("clear_int1()", &lis);
+        }
 
-    /* read stored fifo data into `fifo' struct */
-    if (lis3dh_read_fifo(&lis, &fifo)) {
-        quit("read_fifo()", &lis);
-    }
+        /* read stored fifo data into `fifo' struct */
+        if (lis3dh_read_fifo(&lis, &fifo)) {
+            quit("read_fifo()", &lis);
+        }
 
-    for(k=0; k<fifo.size; k++) {
-        printf("%04.04f %04.04f %04.04f %04.04f\n",
-            fifo.x[k], fifo.y[k], fifo.z[k],
-            mag(fifo.x[k], fifo.y[k], fifo.z[k]));
+        for(k=0; k<fifo.size; k++) {
+            printf("%04.04f %04.04f %04.04f %04.04f\n",
+                fifo.x[k], fifo.y[k], fifo.z[k],
+                mag(fifo.x[k], fifo.y[k], fifo.z[k]));
+        }
+
+        lis3dh_reference(&lis);
     }
     
     /* unregister interrupt */