diff --git a/src/ds1307/ds1307.cxx b/src/ds1307/ds1307.cxx
index bc748e6b..8c7b167e 100644
--- a/src/ds1307/ds1307.cxx
+++ b/src/ds1307/ds1307.cxx
@@ -50,10 +50,10 @@ DS1307::~DS1307()
   mraa_i2c_stop(m_i2c);
 }
 
-mraa_result_t DS1307::writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
+mraa::Result DS1307::writeBytes(uint8_t reg, uint8_t *buffer, int len)
 {
   if (!len || !buffer)
-    return MRAA_ERROR_INVALID_PARAMETER;
+    return mraa::ERROR_INVALID_PARAMETER;
 
   // create a buffer 1 byte larger than the supplied buffer,
   // store the register in the first byte
@@ -67,10 +67,10 @@ mraa_result_t DS1307::writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
 
   mraa_i2c_address(m_i2c, DS1307_I2C_ADDR);
 
-  return mraa_i2c_write(m_i2c, buf2, len + 1);
+  return (mraa::Result) mraa_i2c_write(m_i2c, buf2, len + 1);
 }
 
-uint8_t DS1307::readBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
+int DS1307::readBytes(uint8_t reg, uint8_t *buffer, int len)
 {
   if (!len || !buffer)
     return 0;
@@ -166,7 +166,7 @@ bool DS1307::setTime()
   return writeBytes(0, buffer, 7);
 }
 
-mraa_result_t DS1307::enableClock()
+mraa::Result DS1307::enableClock()
 {
   // the oscillator enable bit is the high bit of reg 0
   // so read it, clear it, and write it back.
@@ -179,7 +179,7 @@ mraa_result_t DS1307::enableClock()
   return writeBytes(0, &buf, 1);
 }
 
-mraa_result_t DS1307::disableClock()
+mraa::Result DS1307::disableClock()
 {
   // the oscillator enable bit is the high bit of reg 0
   // so read it, set it, and write it back.
diff --git a/src/ds1307/ds1307.h b/src/ds1307/ds1307.h
index be169bfd..376f3fb2 100644
--- a/src/ds1307/ds1307.h
+++ b/src/ds1307/ds1307.h
@@ -27,7 +27,7 @@
 #pragma once
 
 #include <string>
-#include <mraa/i2c.h>
+#include <mraa/i2c.hpp>
 
 #define DS1307_I2C_BUS     0
 #define DS1307_I2C_ADDR    0x68
@@ -102,7 +102,7 @@ namespace upm {
      *
      * @return 0 (MRAA_SUCCESS) if successful; non-zero otherwise
      */
-    mraa_result_t enableClock();
+    mraa::Result enableClock();
 
     /**
      * Disables the oscillator on the clock. This prevents the clock
@@ -110,7 +110,7 @@ namespace upm {
      *
      * @return 0 (MRAA_SUCCESS) if successful; non-zero otherwise
      */
-    mraa_result_t disableClock();
+    mraa::Result disableClock();
 
     /**
      * Writes value(s) into registers
@@ -120,7 +120,7 @@ namespace upm {
      * @param len Number of bytes to write
      * @return 0 (MRAA_SUCCESS) if successful; non-zero otherwise
      */
-    mraa_result_t writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len);
+    mraa::Result writeBytes(uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * Reads value(s) from registers
@@ -130,7 +130,7 @@ namespace upm {
      * @param len Number of bytes to read
      * @return Number of bytes read
      */
-    uint8_t readBytes(uint8_t reg, uint8_t *buffer, unsigned int len);
+    int readBytes(uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * Converts a BCD value into decimal
diff --git a/src/ds1307/javaupm_ds1307.i b/src/ds1307/javaupm_ds1307.i
index 2171974a..4fecc345 100644
--- a/src/ds1307/javaupm_ds1307.i
+++ b/src/ds1307/javaupm_ds1307.i
@@ -1,24 +1,10 @@
 %module javaupm_ds1307
 %include "../upm.i"
 %include "arrays_java.i";
+%include "../java_buffer.i"
 
 %{
     #include "ds1307.h"
 %}
 
-%typemap(jni) (uint8_t *buffer, unsigned int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buffer, unsigned int len) "byte[]";
-%typemap(jstype) (uint8_t *buffer, unsigned int len) "byte[]";
-
-%typemap(javain) (uint8_t *buffer, unsigned int len) "$javainput";
-
-%typemap(in) (uint8_t *buffer, unsigned int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buffer, unsigned int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "ds1307.h"
diff --git a/src/gas/gas.cxx b/src/gas/gas.cxx
index 64415f1d..1d256825 100644
--- a/src/gas/gas.cxx
+++ b/src/gas/gas.cxx
@@ -46,7 +46,7 @@ Gas::~Gas() {
 }
 
 int
-Gas::getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples,
+Gas::getSampledWindow (unsigned int freqMS, int numberOfSamples,
                             uint16_t * buffer) {
     int sampleIdx = 0;
 
@@ -70,7 +70,7 @@ Gas::getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples,
 
 int
 Gas::findThreshold (thresholdContext* ctx, unsigned int threshold,
-                                uint16_t * buffer, unsigned int len) {
+                                uint16_t * buffer, int len) {
     long sum = 0;
     for (unsigned int i = 0; i < len; i++) {
         sum += buffer[i];
diff --git a/src/gas/gas.h b/src/gas/gas.h
index 13eb0b27..dbc68bbb 100644
--- a/src/gas/gas.h
+++ b/src/gas/gas.h
@@ -65,7 +65,7 @@ class Gas {
          * @param numberOfSamples Number of sample to sample for this window
          * @param buffer Buffer with sampled data
          */
-        virtual int getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples, uint16_t * buffer);
+        virtual int getSampledWindow (unsigned int freqMS, int numberOfSamples, uint16_t * buffer);
 
         /**
          * Given the sampled buffer, this method returns TRUE/FALSE if the threshold
@@ -76,7 +76,7 @@ class Gas {
          * @param buffer Buffer with samples
          * @param len Buffer length
          */
-        virtual int findThreshold (thresholdContext* ctx, unsigned int threshold, uint16_t * buffer, unsigned int len);
+        virtual int findThreshold (thresholdContext* ctx, unsigned int threshold, uint16_t * buffer, int len);
 
         /**
          * Returns average data for the sampled window
diff --git a/src/gas/javaupm_gas.i b/src/gas/javaupm_gas.i
index ef7b03b6..78d38727 100644
--- a/src/gas/javaupm_gas.i
+++ b/src/gas/javaupm_gas.i
@@ -11,33 +11,33 @@
     #include "tp401.h"
 %}
 
-%typemap(jni) (uint16_t *buffer, unsigned int len) "jshortArray";
-%typemap(jtype) (uint16_t *buffer, unsigned int len) "short[]";
-%typemap(jstype) (uint16_t *buffer, unsigned int len) "short[]";
+%typemap(jni) (uint16_t *buffer, int len) "jshortArray";
+%typemap(jtype) (uint16_t *buffer, int len) "short[]";
+%typemap(jstype) (uint16_t *buffer, int len) "short[]";
 
-%typemap(javain) (uint16_t *buffer, unsigned int len) "$javainput";
+%typemap(javain) (uint16_t *buffer, int len) "$javainput";
 
-%typemap(in) (uint16_t *buffer, unsigned int len) {
+%typemap(in) (uint16_t *buffer, int len) {
         $1 = (uint16_t *) JCALL2(GetShortArrayElements, jenv, $input, NULL);
         $2 = JCALL1(GetArrayLength, jenv, $input);
 }
 
-%typemap(freearg) (uint16_t *buffer, unsigned int len) {
+%typemap(freearg) (uint16_t *buffer, int len) {
         JCALL3(ReleaseShortArrayElements, jenv, $input, (jshort *)$1, 0);
 }
 
-%typemap(jni) (unsigned int numberOfSamples, uint16_t *buffer) "jshortArray";
-%typemap(jtype) (unsigned int numberOfSamples, uint16_t *buffer) "short[]";
-%typemap(jstype) (unsigned int numberOfSamples, uint16_t *buffer) "short[]";
+%typemap(jni) (int numberOfSamples, uint16_t *buffer) "jshortArray";
+%typemap(jtype) (int numberOfSamples, uint16_t *buffer) "short[]";
+%typemap(jstype) (int numberOfSamples, uint16_t *buffer) "short[]";
 
-%typemap(javain) (unsigned int numberOfSamples, uint16_t *buffer) "$javainput";
+%typemap(javain) (int numberOfSamples, uint16_t *buffer) "$javainput";
 
-%typemap(in) (unsigned int numberOfSamples, uint16_t *buffer) {
+%typemap(in) (int numberOfSamples, uint16_t *buffer) {
         $2 = (uint16_t *) JCALL2(GetShortArrayElements, jenv, $input, NULL);
         $1 = JCALL1(GetArrayLength, jenv, $input);
 }
 
-%typemap(freearg) (unsigned int numberOfSamples, uint16_t *buffer) {
+%typemap(freearg) (int numberOfSamples, uint16_t *buffer) {
         JCALL3(ReleaseShortArrayElements, jenv, $input, (jshort *)$2, 0);
 }
 
diff --git a/src/grovemd/grovemd.cxx b/src/grovemd/grovemd.cxx
index 2a965dd7..78a3eeba 100644
--- a/src/grovemd/grovemd.cxx
+++ b/src/grovemd/grovemd.cxx
@@ -45,12 +45,12 @@ GroveMD::GroveMD(int bus, uint8_t address)
 
   // this board *requires* 100Khz i2c bus only
   mraa_result_t rv;
-  if ( (rv = mraa_i2c_frequency(m_i2c, MRAA_I2C_STD)) != MRAA_SUCCESS )
-    {
-      cerr << "GroveMD: Could not set i2c frequency (MRAA_I2C_STD). " << endl;
-      mraa_result_print(rv);
-      return;
-    }
+  //if ( (rv = mraa_i2c_frequency(m_i2c, MRAA_I2C_STD)) != MRAA_SUCCESS )
+    //{
+      //cerr << "GroveMD: Could not set i2c frequency (MRAA_I2C_STD). " << endl;
+      //mraa_result_print(rv);
+      //return;
+    //}
 
   if (mraa_i2c_address(m_i2c, m_addr))
     {
diff --git a/src/grovescam/grovescam.cxx b/src/grovescam/grovescam.cxx
index 222848ce..18432399 100644
--- a/src/grovescam/grovescam.cxx
+++ b/src/grovescam/grovescam.cxx
@@ -105,7 +105,7 @@ bool GROVESCAM::dataAvailable(unsigned int millis)
     return false;
 }
 
-int GROVESCAM::readData(uint8_t *buffer, size_t len)
+int GROVESCAM::readData(uint8_t *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -118,7 +118,7 @@ int GROVESCAM::readData(uint8_t *buffer, size_t len)
   return rv;
 }
 
-int GROVESCAM::writeData(uint8_t *buffer, size_t len)
+int GROVESCAM::writeData(uint8_t *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
diff --git a/src/grovescam/grovescam.h b/src/grovescam/grovescam.h
index 34b4e6f8..052cdba3 100644
--- a/src/grovescam/grovescam.h
+++ b/src/grovescam/grovescam.h
@@ -117,7 +117,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes read
      */
-    int readData(uint8_t *buffer, size_t len);
+    int readData(uint8_t *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -126,7 +126,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(uint8_t *buffer, size_t len);
+    int writeData(uint8_t *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. For this device, the default
diff --git a/src/grovescam/javaupm_grovescam.i b/src/grovescam/javaupm_grovescam.i
index 5f8a789d..bd352b6e 100644
--- a/src/grovescam/javaupm_grovescam.i
+++ b/src/grovescam/javaupm_grovescam.i
@@ -1,23 +1,9 @@
 %module javaupm_grovescam
 %include "../upm.i"
+%include "../java_buffer.i"
 
 %{
     #include "grovescam.h"
 %}
 
-%typemap(jni) (uint8_t *buffer, size_t len) "jbyteArray";
-%typemap(jtype) (uint8_t *buffer, size_t len) "byte[]";
-%typemap(jstype) (uint8_t *buffer, size_t len) "byte[]";
-
-%typemap(javain) (uint8_t *buffer, size_t len) "$javainput";
-
-%typemap(in) (uint8_t *buffer, size_t len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buffer, size_t len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "grovescam.h"
diff --git a/src/hm11/hm11.cxx b/src/hm11/hm11.cxx
index e033eaf4..81e33be1 100644
--- a/src/hm11/hm11.cxx
+++ b/src/hm11/hm11.cxx
@@ -89,7 +89,7 @@ bool HM11::dataAvailable(unsigned int millis)
     return false;
 }
 
-int HM11::readData(char *buffer, size_t len)
+int HM11::readData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -102,7 +102,7 @@ int HM11::readData(char *buffer, size_t len)
   return rv;
 }
 
-int HM11::writeData(char *buffer, size_t len)
+int HM11::writeData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
diff --git a/src/hm11/hm11.h b/src/hm11/hm11.h
index 59aef369..4b59f5f2 100644
--- a/src/hm11/hm11.h
+++ b/src/hm11/hm11.h
@@ -111,7 +111,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes read
      */
-    int readData(char *buffer, size_t len);
+    int readData(char *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -120,7 +120,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. For this device, the default
diff --git a/src/hm11/javaupm_hm11.i b/src/hm11/javaupm_hm11.i
index 17a3cbc9..7475551d 100644
--- a/src/hm11/javaupm_hm11.i
+++ b/src/hm11/javaupm_hm11.i
@@ -1,6 +1,7 @@
 %module javaupm_hm11
 %include "../upm.i"
 %include "carrays.i"
+%include "../java_buffer.i"
 
 %{
     #include "hm11.h"
diff --git a/src/hmtrp/hmtrp.cxx b/src/hmtrp/hmtrp.cxx
index cfc0b6b5..95722dc9 100644
--- a/src/hmtrp/hmtrp.cxx
+++ b/src/hmtrp/hmtrp.cxx
@@ -94,7 +94,7 @@ bool HMTRP::dataAvailable(unsigned int millis)
     return false;
 }
 
-int HMTRP::readData(char *buffer, size_t len, int millis)
+int HMTRP::readData(char *buffer, int len, int millis)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -114,7 +114,7 @@ int HMTRP::readData(char *buffer, size_t len, int millis)
   return rv;
 }
 
-int HMTRP::writeData(char *buffer, size_t len)
+int HMTRP::writeData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
diff --git a/src/hmtrp/hmtrp.h b/src/hmtrp/hmtrp.h
index 9aa7b3d7..47d272e7 100644
--- a/src/hmtrp/hmtrp.h
+++ b/src/hmtrp/hmtrp.h
@@ -124,7 +124,7 @@ namespace upm {
      * waiting forever (default).
      * @return Number of bytes read; 0 if timed out and millis is >= 0
      */
-    int readData(char *buffer, size_t len, int millis=-1);
+    int readData(char *buffer, int len, int millis=-1);
 
     /**
      * Writes the data in the buffer to the device
@@ -133,7 +133,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. The default
diff --git a/src/hmtrp/javaupm_hmtrp.i b/src/hmtrp/javaupm_hmtrp.i
index 8f1d6caa..c02e34a1 100644
--- a/src/hmtrp/javaupm_hmtrp.i
+++ b/src/hmtrp/javaupm_hmtrp.i
@@ -2,6 +2,7 @@
 %include "../upm.i"
 %include "stdint.i"
 %include "typemaps.i"
+%include "../java_buffer.i"
 
 %apply uint32_t *OUTPUT { uint32_t *freq, uint32_t *dataRate };
 %apply uint16_t *OUTPUT { uint16_t *rxBandwidth };
diff --git a/src/java_buffer.i b/src/java_buffer.i
new file mode 100644
index 00000000..6fec084d
--- /dev/null
+++ b/src/java_buffer.i
@@ -0,0 +1,45 @@
+
+%typemap(jni) (uint8_t *buffer, int len) "jbyteArray";
+%typemap(jtype) (uint8_t *buffer, int len) "byte[]";
+%typemap(jstype) (uint8_t *buffer, int len) "byte[]";
+
+%typemap(javain) (uint8_t *buffer, int len) "$javainput";
+
+%typemap(in) (uint8_t *buffer, int len) {
+        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
+        $2 = JCALL1(GetArrayLength, jenv, $input);
+}
+
+%typemap(freearg) (uint8_t *buffer, int len) {
+        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
+}
+
+%typemap(jni) (uint8_t *pkt, int len) "jbyteArray";
+%typemap(jtype) (uint8_t *pkt, int len) "byte[]";
+%typemap(jstype) (uint8_t *pkt, int len) "byte[]";
+
+%typemap(javain) (uint8_t *pkt, int len) "$javainput";
+
+%typemap(in) (uint8_t *pkt, int len) {
+        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
+        $2 = JCALL1(GetArrayLength, jenv, $input);
+}
+
+%typemap(freearg) (uint8_t *pkt, int len) {
+        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
+}
+
+%typemap(jni) (char *buffer, int len) "jbyteArray";
+%typemap(jtype) (char *buffer, int len) "byte[]";
+%typemap(jstype) (char *buffer, int len) "byte[]";
+
+%typemap(javain) (char *buffer, int len) "$javainput";
+
+%typemap(in) (char *buffer, int len) {
+        $1 = (char *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
+        $2 = JCALL1(GetArrayLength, jenv, $input);
+}
+
+%typemap(freearg) (char *buffer, int len) {
+        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
+}
diff --git a/src/lcd/javaupm_i2clcd.i b/src/lcd/javaupm_i2clcd.i
index 71839978..4d3cd20a 100644
--- a/src/lcd/javaupm_i2clcd.i
+++ b/src/lcd/javaupm_i2clcd.i
@@ -6,18 +6,6 @@
 
 %apply signed char[] {uint8_t []};
 
-%{
-    #include "lcd.h"
-    #include "ssd.h"
-    #include "ssd1327.h"
-    #include "ssd1308.h"
-    #include "eboled.h"
-    #include "lcm1602.h"
-    #include "jhd1313m1.h"
-    #include "sainsmartks.h"
-%}
-
-
 %typemap(jni) (uint8_t *data, int bytes) "jbyteArray";
 %typemap(jtype) (uint8_t *data, int bytes) "byte[]";
 %typemap(jstype) (uint8_t *data, int bytes) "byte[]";
@@ -33,6 +21,17 @@
         JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
 }
 
+%{
+    #include "lcd.h"
+    #include "ssd.h"
+    #include "ssd1327.h"
+    #include "ssd1308.h"
+    #include "eboled.h"
+    #include "lcm1602.h"
+    #include "jhd1313m1.h"
+    #include "sainsmartks.h"
+%}
+
 %include "lcd.h"
 %include "ssd.h"
 %include "ssd1327.h"
diff --git a/src/lsm9ds0/javaupm_lsm9ds0.i b/src/lsm9ds0/javaupm_lsm9ds0.i
index ca63616d..efc15125 100644
--- a/src/lsm9ds0/javaupm_lsm9ds0.i
+++ b/src/lsm9ds0/javaupm_lsm9ds0.i
@@ -3,6 +3,7 @@
 %include "cpointer.i"
 %include "typemaps.i"
 %include "arrays_java.i";
+%include "../java_buffer.i"
 
 %feature("director") IsrCallback;
 
@@ -12,10 +13,6 @@
 %apply int {mraa::Edge};
 %apply float *INOUT { float *x, float *y, float *z };
 
-%{
-    #include "lsm9ds0.h"
-%}
-
 %typemap(jni) float* "jfloatArray"
 %typemap(jstype) float* "float[]"
 %typemap(jtype) float* "float[]"
@@ -46,19 +43,8 @@
 %ignore getGyroscope(float *, float *, float *);
 %ignore getMagnetometer(float *, float *, float *);
 
-%typemap(jni) (uint8_t *buf, int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buf, int len) "byte[]";
-%typemap(jstype) (uint8_t *buf, int len) "byte[]";
-
-%typemap(javain) (uint8_t *buf, int len) "$javainput";
-
-%typemap(in) (uint8_t *buf, int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buf, int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
+%{
+    #include "lsm9ds0.h"
+%}
 
 %include "lsm9ds0.h"
diff --git a/src/lsm9ds0/lsm9ds0.cxx b/src/lsm9ds0/lsm9ds0.cxx
index 32e568cf..045dc633 100644
--- a/src/lsm9ds0/lsm9ds0.cxx
+++ b/src/lsm9ds0/lsm9ds0.cxx
@@ -287,7 +287,7 @@ uint8_t LSM9DS0::readReg(DEVICE_T dev, uint8_t reg)
   return device->readReg(reg);
 }
 
-void LSM9DS0::readRegs(DEVICE_T dev, uint8_t reg, uint8_t *buf, int len)
+void LSM9DS0::readRegs(DEVICE_T dev, uint8_t reg, uint8_t *buffer, int len)
 {
   mraa::I2c *device;
 
@@ -302,7 +302,7 @@ void LSM9DS0::readRegs(DEVICE_T dev, uint8_t reg, uint8_t *buf, int len)
 
   // We need to set the high bit of the register to enable
   // auto-increment mode for reading multiple registers in one go.
-  device->readBytesReg(reg | m_autoIncrementMode, buf, len);
+  device->readBytesReg(reg | m_autoIncrementMode, buffer, len);
 }
 
 bool LSM9DS0::writeReg(DEVICE_T dev, uint8_t reg, uint8_t val)
diff --git a/src/lsm9ds0/lsm9ds0.h b/src/lsm9ds0/lsm9ds0.h
index 6580c25e..7b47fbbd 100644
--- a/src/lsm9ds0/lsm9ds0.h
+++ b/src/lsm9ds0/lsm9ds0.h
@@ -1126,7 +1126,7 @@ namespace upm {
      * @param len the number of registers to read
      * @return the value of the register
      */
-    void readRegs(DEVICE_T dev, uint8_t reg, uint8_t *buf, int len);
+    void readRegs(DEVICE_T dev, uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * write to a register
diff --git a/src/m24lr64e/javaupm_m24lr64e.i b/src/m24lr64e/javaupm_m24lr64e.i
index ae61d31d..78142030 100644
--- a/src/m24lr64e/javaupm_m24lr64e.i
+++ b/src/m24lr64e/javaupm_m24lr64e.i
@@ -2,24 +2,10 @@
 %include "../upm.i"
 %include "stdint.i"
 %include "arrays_java.i";
+%include "../java_buffer.i"
 
 %{
     #include "m24lr64e.h"
 %}
 
-%typemap(jni) (uint8_t *buf, unsigned int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buf, unsigned int len) "byte[]";
-%typemap(jstype) (uint8_t *buf, unsigned int len) "byte[]";
-
-%typemap(javain) (uint8_t *buf, unsigned int len) "$javainput";
-
-%typemap(in) (uint8_t *buf, unsigned int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buf, unsigned int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "m24lr64e.h"
diff --git a/src/m24lr64e/m24lr64e.cxx b/src/m24lr64e/m24lr64e.cxx
index 76355bf9..3fe9bcbd 100644
--- a/src/m24lr64e/m24lr64e.cxx
+++ b/src/m24lr64e/m24lr64e.cxx
@@ -163,9 +163,9 @@ uint8_t M24LR64E::getAFI()
   return EEPROM_Read_Byte(AFI_ADDR);
 }
 
-void M24LR64E::getUID(uint8_t* buf)
+void M24LR64E::getUID(uint8_t* buffer)
 {
-  EEPROM_Read_Bytes(UID_ADDR,buf,UID_LENGTH);    
+  EEPROM_Read_Bytes(UID_ADDR, buffer, UID_LENGTH);
 }
 
 uint32_t M24LR64E::getMemorySize()
@@ -184,14 +184,14 @@ void M24LR64E::clearMemory()
   }
 }
 
-void M24LR64E::writeByte(unsigned int address, uint8_t data)
+mraa::Result M24LR64E::writeByte(unsigned int address, uint8_t data)
 {
-  EEPROM_Write_Byte(address, data);
+  return EEPROM_Write_Byte(address, data);
 }
 
-void M24LR64E::writeBytes(unsigned int address, uint8_t* buf, unsigned int len)
+mraa::Result M24LR64E::writeBytes(unsigned int address, uint8_t* buffer, int len)
 {
-  EEPROM_Write_Bytes(address, buf, len);
+  return EEPROM_Write_Bytes(address, buffer, len);
 }
 
 uint8_t M24LR64E::readByte(unsigned int address)
@@ -199,31 +199,34 @@ uint8_t M24LR64E::readByte(unsigned int address)
   return EEPROM_Read_Byte(address);
 }
 
-void M24LR64E::readBytes(unsigned int address, uint8_t* buf, unsigned int len)
+int M24LR64E::readBytes(unsigned int address, uint8_t* buffer, int len)
 {
-  EEPROM_Read_Bytes(address, buf, len);
+  return EEPROM_Read_Bytes(address, buffer, len);
 }
 
-void M24LR64E::EEPROM_Write_Byte(unsigned int address, uint8_t data)
+mraa::Result M24LR64E::EEPROM_Write_Byte(unsigned int address, uint8_t data)
 {
   const int pktLen = 3;
   uint8_t buf[pktLen];
+  mraa::Result rv;
   
   buf[0] = ((address >> 8) & 0xff);
   buf[1] = (address & 0xff);
   buf[2] = data;
 
-  if (m_i2c.write(buf, pktLen))
+  if ((rv = m_i2c.write(buf, pktLen)))
     cerr << __FUNCTION__ << "@" << __LINE__ << ": write failed" << endl;
 
   usleep(I2C_WRITE_TIME * 1000);
+  return rv;
 }
 
-void M24LR64E::EEPROM_Write_Bytes(unsigned int address, uint8_t* data,
-                                  unsigned int len)
+mraa::Result M24LR64E::EEPROM_Write_Bytes(unsigned int address, uint8_t* data,
+                                  int len)
 {
   const int pktLen = 2 + len;
   uint8_t buf[pktLen];
+  mraa::Result rv;
   
   buf[0] = ((address >> 8) & 0xff);
   buf[1] = (address & 0xff);
@@ -231,10 +234,12 @@ void M24LR64E::EEPROM_Write_Bytes(unsigned int address, uint8_t* data,
   for (int i=0; i<len; i++)
     buf[2+i] = data[i];
 
-  if (m_i2c.write(buf, pktLen))
+  if ((rv = m_i2c.write(buf, pktLen)))
     cerr << __FUNCTION__ << "@" << __LINE__ << ": write failed" << endl;
 
   usleep(I2C_WRITE_TIME * 1000);
+
+  return rv;
 }
 
 uint8_t M24LR64E::EEPROM_Read_Byte(unsigned int address)
@@ -265,8 +270,8 @@ uint8_t M24LR64E::EEPROM_Read_Byte(unsigned int address)
   return buf[0];
 }
 
-unsigned int M24LR64E::EEPROM_Read_Bytes(unsigned int address, 
-                                         uint8_t* buf, unsigned int len)
+int M24LR64E::EEPROM_Read_Bytes(unsigned int address, 
+                                         uint8_t* buffer, int len)
 {
   const int apktLen = 2;
   uint8_t abuf[apktLen];
@@ -280,7 +285,7 @@ unsigned int M24LR64E::EEPROM_Read_Bytes(unsigned int address,
       return false;
     }
 
-  int rv = m_i2c.read(buf, len);
+  int rv = m_i2c.read(buffer, len);
   if (rv != len)
     {
       cerr << __FUNCTION__ << "@" << __LINE__ << ": read failed" << endl;
diff --git a/src/m24lr64e/m24lr64e.h b/src/m24lr64e/m24lr64e.h
index 54236c92..053b6bff 100644
--- a/src/m24lr64e/m24lr64e.h
+++ b/src/m24lr64e/m24lr64e.h
@@ -218,7 +218,7 @@ namespace upm {
      *
      * @param buf Buffer to hold the returned UID. Must be UID_LENGTH bytes.
      */
-    void getUID(uint8_t* buf);
+    void getUID(uint8_t* buffer);
 
     /**
      * Returns the memory size
@@ -239,7 +239,7 @@ namespace upm {
      * @param address Address to write to
      * @param data Data to write
      */
-    void writeByte(unsigned int address, uint8_t data);
+    mraa::Result writeByte(unsigned int address, uint8_t data);
 
     /**
      * Writes bytes to the EEPROM
@@ -248,7 +248,7 @@ namespace upm {
      * @param data Data to write
      * @param data Length of the data buffer
      */
-    void writeBytes(unsigned int address, uint8_t* buf, unsigned int len);
+    mraa::Result writeBytes(unsigned int address, uint8_t* buffer, int len);
 
     /**
      * Reads a byte from the EEPROM
@@ -265,16 +265,16 @@ namespace upm {
      * @param buffer Buffer to store data
      * @param len Number of bytes to read
      */
-    void readBytes(unsigned int address, uint8_t* buf, unsigned int len);
+    int readBytes(unsigned int address, uint8_t* buffer, int len);
 
   protected:
     mraa::I2c m_i2c;
-    void EEPROM_Write_Byte(unsigned int address, uint8_t data);
-    void EEPROM_Write_Bytes(unsigned int address, uint8_t* data,
-                            unsigned int len);
+    mraa::Result EEPROM_Write_Byte(unsigned int address, uint8_t data);
+    mraa::Result EEPROM_Write_Bytes(unsigned int address, uint8_t* data,
+                            int len);
     uint8_t EEPROM_Read_Byte(unsigned int address);
-    unsigned int EEPROM_Read_Bytes(unsigned int address, 
-                                   uint8_t* buf, unsigned int len);
+    int EEPROM_Read_Bytes(unsigned int address, 
+                                   uint8_t* buffer, int len);
 
   private:
     uint8_t m_addr;
diff --git a/src/mhz16/javaupm_mhz16.i b/src/mhz16/javaupm_mhz16.i
index 9a555a71..1d50fb71 100644
--- a/src/mhz16/javaupm_mhz16.i
+++ b/src/mhz16/javaupm_mhz16.i
@@ -3,8 +3,7 @@
 %include "cpointer.i"
 %include "typemaps.i"
 %include "arrays_java.i";
-
-%apply signed char[] {unsigned char *};
+%include "../java_buffer.i"
 
 %apply int *OUTPUT { int *gas, int *temp };
 
diff --git a/src/mhz16/mhz16.cxx b/src/mhz16/mhz16.cxx
index 38b24714..93884a55 100644
--- a/src/mhz16/mhz16.cxx
+++ b/src/mhz16/mhz16.cxx
@@ -91,7 +91,7 @@ bool MHZ16::dataAvailable(unsigned int millis)
     return false;
 }
 
-int MHZ16::readData(char *buffer, size_t len)
+int MHZ16::readData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -107,7 +107,7 @@ int MHZ16::readData(char *buffer, size_t len)
   return rv;
 }
 
-int MHZ16::writeData(char *buffer, size_t len)
+int MHZ16::writeData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -156,7 +156,7 @@ bool MHZ16::setupTty(speed_t baud)
   return true;
 }
 
-bool MHZ16::verifyPacket(unsigned char *pkt)
+bool MHZ16::verifyPacket(uint8_t *pkt, int len)
 {
   if (pkt[0] != 0xff || pkt[1] != 0x86)
     {
@@ -193,7 +193,7 @@ bool MHZ16::getData(int *gas, int *temp)
       return false;
     }
   
-  if (!verifyPacket(packet))
+  if (!verifyPacket(packet, 9))
     {
       cerr << __FUNCTION__ << ": Packet verify failed." << endl;
       return false;
diff --git a/src/mhz16/mhz16.h b/src/mhz16/mhz16.h
index 7cf822d9..6389aa29 100644
--- a/src/mhz16/mhz16.h
+++ b/src/mhz16/mhz16.h
@@ -106,7 +106,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes read
      */
-    int readData(char *buffer, size_t len);
+    int readData(char *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -115,7 +115,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. The default
@@ -132,7 +132,7 @@ namespace upm {
      * @param pkt Packet to check
      * @return True if the checksum is valid, false otherwise
      */
-    bool verifyPacket(unsigned char *pkt);
+    bool verifyPacket(uint8_t *pkt, int len);
 
     /**
      * Queries the sensor and returns gas (CO2) concentration and
diff --git a/src/mic/javaupm_mic.i b/src/mic/javaupm_mic.i
index cdb0ce20..4d3f5d52 100644
--- a/src/mic/javaupm_mic.i
+++ b/src/mic/javaupm_mic.i
@@ -7,33 +7,33 @@
     #include "mic.h"
 %}
 
-%typemap(jni) (uint16_t *buffer, unsigned int len) "jshortArray";
-%typemap(jtype) (uint16_t *buffer, unsigned int len) "short[]";
-%typemap(jstype) (uint16_t *buffer, unsigned int len) "short[]";
+%typemap(jni) (uint16_t *buffer, int len) "jshortArray";
+%typemap(jtype) (uint16_t *buffer, int len) "short[]";
+%typemap(jstype) (uint16_t *buffer, int len) "short[]";
 
-%typemap(javain) (uint16_t *buffer, unsigned int len) "$javainput";
+%typemap(javain) (uint16_t *buffer, int len) "$javainput";
 
-%typemap(in) (uint16_t *buffer, unsigned int len) {
+%typemap(in) (uint16_t *buffer, int len) {
         $1 = (uint16_t *) JCALL2(GetShortArrayElements, jenv, $input, NULL);
         $2 = JCALL1(GetArrayLength, jenv, $input);
 }
 
-%typemap(freearg) (uint16_t *buffer, unsigned int len) {
+%typemap(freearg) (uint16_t *buffer, int len) {
         JCALL3(ReleaseShortArrayElements, jenv, $input, (jshort *)$1, 0);
 }
 
-%typemap(jni) (unsigned int numberOfSamples, uint16_t *buffer) "jshortArray";
-%typemap(jtype) (unsigned int numberOfSamples, uint16_t *buffer) "short[]";
-%typemap(jstype) (unsigned int numberOfSamples, uint16_t *buffer) "short[]";
+%typemap(jni) (int numberOfSamples, uint16_t *buffer) "jshortArray";
+%typemap(jtype) (int numberOfSamples, uint16_t *buffer) "short[]";
+%typemap(jstype) (int numberOfSamples, uint16_t *buffer) "short[]";
 
-%typemap(javain) (unsigned int numberOfSamples, uint16_t *buffer) "$javainput";
+%typemap(javain) (int numberOfSamples, uint16_t *buffer) "$javainput";
 
-%typemap(in) (unsigned int numberOfSamples, uint16_t *buffer) {
+%typemap(in) (int numberOfSamples, uint16_t *buffer) {
         $2 = (uint16_t *) JCALL2(GetShortArrayElements, jenv, $input, NULL);
         $1 = JCALL1(GetArrayLength, jenv, $input);
 }
 
-%typemap(freearg) (unsigned int numberOfSamples, uint16_t *buffer) {
+%typemap(freearg) (int numberOfSamples, uint16_t *buffer) {
         JCALL3(ReleaseShortArrayElements, jenv, $input, (jshort *)$2, 0);
 }
 
diff --git a/src/mic/mic.cxx b/src/mic/mic.cxx
index 79073269..b2688615 100644
--- a/src/mic/mic.cxx
+++ b/src/mic/mic.cxx
@@ -48,7 +48,7 @@ Microphone::~Microphone() {
 }
 
 int
-Microphone::getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples,
+Microphone::getSampledWindow (unsigned int freqMS, int numberOfSamples,
                             uint16_t * buffer) {
     int sampleIdx = 0;
 
@@ -72,7 +72,7 @@ Microphone::getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples,
 
 int
 Microphone::findThreshold (thresholdContext* ctx, unsigned int threshold,
-                                uint16_t * buffer, unsigned int len) {
+                                uint16_t * buffer, int len) {
     long sum = 0;
     for (unsigned int i = 0; i < len; i++) {
         sum += buffer[i];
diff --git a/src/mic/mic.h b/src/mic/mic.h
index e0a8ee2f..70033797 100644
--- a/src/mic/mic.h
+++ b/src/mic/mic.h
@@ -80,7 +80,7 @@ class Microphone {
          * @param numberOfSamples Number of sample to sample for this window
          * @param buffer Buffer with sampled data
          */
-        int getSampledWindow (unsigned int freqMS, unsigned int numberOfSamples, uint16_t * buffer);
+        int getSampledWindow (unsigned int freqMS, int numberOfSamples, uint16_t * buffer);
 
         /**
          * Given the sampled buffer, this method returns TRUE/FALSE if threshold
@@ -91,7 +91,7 @@ class Microphone {
          * @param buffer Buffer with samples
          * @param len Buffer length
          */
-        int findThreshold (thresholdContext* ctx, unsigned int threshold, uint16_t * buffer, unsigned int len);
+        int findThreshold (thresholdContext* ctx, unsigned int threshold, uint16_t * buffer, int len);
 
         /**
          *
diff --git a/src/mma7455/javaupm_mma7455.i b/src/mma7455/javaupm_mma7455.i
index 160b88f6..3d4724ba 100644
--- a/src/mma7455/javaupm_mma7455.i
+++ b/src/mma7455/javaupm_mma7455.i
@@ -2,13 +2,10 @@
 %include "../upm.i"
 %include "typemaps.i"
 %include "arrays_java.i";
+%include "../java_buffer.i"
 
 %apply short *OUTPUT { short * ptrX, short * ptrY, short * ptrZ };
 
-%{
-    #include "mma7455.h"
-%}
-
 %typemap(jni) short* "jshortArray"
 %typemap(jstype) short* "short[]"
 %typemap(jtype) short* "short[]"
@@ -25,19 +22,8 @@
 
 %ignore readData(short *, short *, short *);
 
-%typemap(jni) (unsigned char *buf, unsigned char size) "jbyteArray";
-%typemap(jtype) (unsigned char *buf, unsigned char size) "byte[]";
-%typemap(jstype) (unsigned char *buf, unsigned char size) "byte[]";
-
-%typemap(javain) (unsigned char *buf, unsigned char size) "$javainput";
-
-%typemap(in) (unsigned char *buf, unsigned char size) {
-        $1 = (unsigned char *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (unsigned char *buf, unsigned char size) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
+%{
+    #include "mma7455.h"
+%}
 
 %include "mma7455.h"
diff --git a/src/mma7455/mma7455.cxx b/src/mma7455/mma7455.cxx
index 74286a3a..f071fae0 100644
--- a/src/mma7455/mma7455.cxx
+++ b/src/mma7455/mma7455.cxx
@@ -50,7 +50,7 @@ MMA7455::MMA7455 (int bus, int devAddr) : m_i2ControlCtx(bus) {
 
     // setting GLVL 0x1 (64LSB/g) and MODE 0x1 (Measurement Mode)
     data = (BIT (MMA7455_GLVL0) | BIT (MMA7455_MODE0));
-    error = ic2WriteReg (MMA7455_MCTL, &data, 0x1);
+    error = i2cWriteReg (MMA7455_MCTL, &data, 0x1);
     if (error != mraa::SUCCESS) {
         std::cout << "ERROR :: MMA7455 instance wan not created (Mode)" << std::endl;
         return;
@@ -80,7 +80,7 @@ MMA7455::calibrate () {
         xyz.value.y += 2 * -xyz.value.y;
         xyz.value.z += 2 * -(xyz.value.z - 64);
 
-        error = ic2WriteReg (MMA7455_XOFFL,  (unsigned char *) &xyz, 0x6);
+        error = i2cWriteReg (MMA7455_XOFFL,  (unsigned char *) &xyz, 0x6);
         if (error != mraa::SUCCESS) {
             return error;
         }
@@ -97,7 +97,7 @@ MMA7455::readData (short * ptrX, short * ptrY, short * ptrZ) {
     int nBytes = 0;
 
     /*do {
-        nBytes = ic2ReadReg (MMA7455_STATUS, &data, 0x1);
+        nBytes = i2cReadReg (MMA7455_STATUS, &data, 0x1);
     } while ( !(data & MMA7455_DRDY) && nBytes == mraa::SUCCESS);
 
     if (nBytes == mraa::SUCCESS) {
@@ -105,7 +105,7 @@ MMA7455::readData (short * ptrX, short * ptrY, short * ptrZ) {
         return mraa::SUCCESS;
     }*/
 
-    nBytes = ic2ReadReg (MMA7455_XOUTL, (unsigned char *) &xyz, 0x6);
+    nBytes = i2cReadReg (MMA7455_XOUTL, (unsigned char *) &xyz, 0x6);
     if (nBytes == 0) {
         std::cout << "NO_GDB :: 2" << std::endl;
         return mraa::ERROR_UNSPECIFIED;
@@ -140,7 +140,7 @@ short *MMA7455::readData() {
 #endif
 
 int
-MMA7455::ic2ReadReg (unsigned char reg, unsigned char * buf, unsigned char size) {
+MMA7455::i2cReadReg (unsigned char reg, uint8_t *buffer, int len) {
     if (mraa::SUCCESS != m_i2ControlCtx.address(m_controlAddr)) {
         return 0;
     }
@@ -153,22 +153,22 @@ MMA7455::ic2ReadReg (unsigned char reg, unsigned char * buf, unsigned char size)
         return 0;
     }
 
-    return (int) m_i2ControlCtx.read(buf, size);
+    return (int) m_i2ControlCtx.read(buffer, len);
 }
 
 mraa::Result
-MMA7455::ic2WriteReg (unsigned char reg, unsigned char * buf, unsigned char size) {
+MMA7455::i2cWriteReg (unsigned char reg, uint8_t *buffer, int len) {
     mraa::Result error = mraa::SUCCESS;
 
-    uint8_t data[size + 1];
+    uint8_t data[len + 1];
     data[0] = reg;
-    memcpy(&data[1], buf, size);
+    memcpy(&data[1], buffer, len);
 
     error = m_i2ControlCtx.address (m_controlAddr);
     if (error != mraa::SUCCESS) {
         return error;
     }
-    error = m_i2ControlCtx.write (data, size + 1);
+    error = m_i2ControlCtx.write (data, len + 1);
     if (error != mraa::SUCCESS) {
         return error;
     }
diff --git a/src/mma7455/mma7455.h b/src/mma7455/mma7455.h
index 08d7b843..e6982f38 100644
--- a/src/mma7455/mma7455.h
+++ b/src/mma7455/mma7455.h
@@ -214,19 +214,19 @@ class MMA7455 {
          *
          *
          * @param reg Register address
-         * @param buf Register data buffer
+         * @param buffer Register data buffer
          * @param size Buffer size
          */
-        int ic2ReadReg (unsigned char reg, unsigned char * buf, unsigned char size);
+        int i2cReadReg (unsigned char reg, uint8_t *buffer, int len);
 
         /**
          *
          *
          * @param reg Register address
-         * @param buf Register data buffer
+         * @param buffer Register data buffer
          * @param size Buffer size
          */
-        mraa::Result ic2WriteReg (unsigned char reg, unsigned char * buf, unsigned char size);
+        mraa::Result i2cWriteReg (unsigned char reg, uint8_t *buffer, int len);
 
     private:
         std::string m_name;
diff --git a/src/mpr121/javaupm_mpr121.i b/src/mpr121/javaupm_mpr121.i
index a9e853f3..f045e0ea 100644
--- a/src/mpr121/javaupm_mpr121.i
+++ b/src/mpr121/javaupm_mpr121.i
@@ -1,24 +1,10 @@
 %module javaupm_mpr121
 %include "../upm.i"
 %include "arrays_java.i";
+%include "../java_buffer.i"
 
 %{
     #include "mpr121.h"
 %}
 
-%typemap(jni) (uint8_t *buffer, unsigned int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buffer, unsigned int len) "byte[]";
-%typemap(jstype) (uint8_t *buffer, unsigned int len) "byte[]";
-
-%typemap(javain) (uint8_t *buffer, unsigned int len) "$javainput";
-
-%typemap(in) (uint8_t *buffer, unsigned int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buffer, unsigned int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "mpr121.h"
diff --git a/src/mpr121/mpr121.cxx b/src/mpr121/mpr121.cxx
index b316c6c4..3462f4cf 100644
--- a/src/mpr121/mpr121.cxx
+++ b/src/mpr121/mpr121.cxx
@@ -44,7 +44,7 @@ MPR121::MPR121(int bus, uint8_t address) : m_i2c(bus)
   m_overCurrentFault = false;
 }
 
-mraa::Result MPR121::writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
+mraa::Result MPR121::writeBytes(uint8_t reg, uint8_t *buffer, int len)
 {
   if (!len || !buffer)
     return mraa::SUCCESS;
@@ -64,17 +64,17 @@ mraa::Result MPR121::writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
   return m_i2c.write(buf2, len + 1);
 }
 
-void MPR121::readBytes(uint8_t reg, uint8_t *buffer, unsigned int len)
+int MPR121::readBytes(uint8_t reg, uint8_t *buffer, int len)
 {
   if (!len || !buffer)
-    return;
+    return 0;
 
   // The usual m_i2c.read() does not work here, so we need to
   // read each byte individually.
   for (int i=0; i<len; i++)
     buffer[i] = m_i2c.readReg(reg + i);
 
-  return;
+  return len;
 }
 
 bool MPR121::configAN3944()
diff --git a/src/mpr121/mpr121.h b/src/mpr121/mpr121.h
index 581b4915..3b01071b 100644
--- a/src/mpr121/mpr121.h
+++ b/src/mpr121/mpr121.h
@@ -93,7 +93,7 @@ namespace upm {
      * @param len Number of bytes to write
      * @return mraa::Result
      */
-    mraa::Result writeBytes(uint8_t reg, uint8_t *buffer, unsigned int len);
+    mraa::Result writeBytes(uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * Reads value(s) from registers
@@ -102,7 +102,7 @@ namespace upm {
      * @param buffer Buffer for data storage
      * @param len Number of bytes to read
      */
-    void readBytes(uint8_t reg, uint8_t *buffer, unsigned int len);
+    int readBytes(uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * Button states
diff --git a/src/mpu9150/javaupm_mpu9150.i b/src/mpu9150/javaupm_mpu9150.i
index 8fd838b4..86580b61 100644
--- a/src/mpu9150/javaupm_mpu9150.i
+++ b/src/mpu9150/javaupm_mpu9150.i
@@ -2,6 +2,7 @@
 %include "../upm.i"
 %include "typemaps.i"
 %include "arrays_java.i"
+%include "../java_buffer.i"
 
 %feature("director") IsrCallback;
 
@@ -34,20 +35,5 @@
 %ignore getGyroscope(float *, float *, float *);
 %ignore getMagnetometer(float *, float *, float *);
 
-%typemap(jni) (uint8_t *buf, int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buf, int len) "byte[]";
-%typemap(jstype) (uint8_t *buf, int len) "byte[]";
-
-%typemap(javain) (uint8_t *buf, int len) "$javainput";
-
-%typemap(in) (uint8_t *buf, int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buf, int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "mpu60x0.h"
 %include "mpu9150.h"
diff --git a/src/mpu9150/mpu60x0.cxx b/src/mpu9150/mpu60x0.cxx
index b48a468a..b03489cf 100644
--- a/src/mpu9150/mpu60x0.cxx
+++ b/src/mpu9150/mpu60x0.cxx
@@ -139,9 +139,9 @@ uint8_t MPU60X0::readReg(uint8_t reg)
   return m_i2c.readReg(reg);
 }
 
-void MPU60X0::readRegs(uint8_t reg, uint8_t *buf, int len)
+void MPU60X0::readRegs(uint8_t reg, uint8_t *buffer, int len)
 {
-  m_i2c.readBytesReg(reg, buf, len);
+  m_i2c.readBytesReg(reg, buffer, len);
 }
 
 bool MPU60X0::writeReg(uint8_t reg, uint8_t val)
diff --git a/src/mpu9150/mpu60x0.h b/src/mpu9150/mpu60x0.h
index d64d4dcf..1ab96d19 100644
--- a/src/mpu9150/mpu60x0.h
+++ b/src/mpu9150/mpu60x0.h
@@ -706,11 +706,11 @@ namespace upm {
      * read contiguous refister into a buffer
      *
      * @param reg the register to start reading at
-     * @param buf the buffer to store the results
+     * @param buffer the buffer to store the results
      * @param len the number of registers to read
      * @return the value of the register
      */
-    void readRegs(uint8_t reg, uint8_t *buf, int len);
+    void readRegs(uint8_t reg, uint8_t *buffer, int len);
 
     /**
      * write to a register
diff --git a/src/nunchuck/javaupm_nunchuck.i b/src/nunchuck/javaupm_nunchuck.i
index 9cadad62..a87273f2 100644
--- a/src/nunchuck/javaupm_nunchuck.i
+++ b/src/nunchuck/javaupm_nunchuck.i
@@ -1,23 +1,9 @@
 %module javaupm_nunchuck
 %include "../upm.i"
+%include "../java_buffer.i"
 
 %{
     #include "nunchuck.h"
 %}
 
-%typemap(jni) (uint8_t *buffer, int len) "jbyteArray";
-%typemap(jtype) (uint8_t *buffer, int len) "byte[]";
-%typemap(jstype) (uint8_t *buffer, int len) "byte[]";
-
-%typemap(javain) (uint8_t *buffer, int len) "$javainput";
-
-%typemap(in) (uint8_t *buffer, int len) {
-        $1 = (uint8_t *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (uint8_t *buffer, int len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
 %include "nunchuck.h"
diff --git a/src/ublox6/javaupm_ublox6.i b/src/ublox6/javaupm_ublox6.i
index 965bf7c2..164bd298 100644
--- a/src/ublox6/javaupm_ublox6.i
+++ b/src/ublox6/javaupm_ublox6.i
@@ -1,25 +1,11 @@
 %module javaupm_ublox6
 %include "../upm.i"
+%include "../java_buffer.i"
 
 %{
     #include "ublox6.h"
     speed_t int_B9600 = B9600;
 %}
 
-%typemap(jni) (char *buffer, size_t len) "jbyteArray";
-%typemap(jtype) (char *buffer, size_t len) "byte[]";
-%typemap(jstype) (char *buffer, size_t len) "byte[]";
-
-%typemap(javain) (char *buffer, size_t len) "$javainput";
-
-%typemap(in) (char *buffer, size_t len) {
-        $1 = (char *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (char *buffer, size_t len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *) $1, 0);
-}
-
 %include "ublox6.h"
 speed_t int_B9600 = B9600;
diff --git a/src/ublox6/ublox6.cxx b/src/ublox6/ublox6.cxx
index 45e440f1..bc282148 100644
--- a/src/ublox6/ublox6.cxx
+++ b/src/ublox6/ublox6.cxx
@@ -87,7 +87,7 @@ bool Ublox6::dataAvailable()
     return false;
 }
 
-int Ublox6::readData(char *buffer, size_t len)
+int Ublox6::readData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -100,7 +100,7 @@ int Ublox6::readData(char *buffer, size_t len)
   return rv;
 }
 
-int Ublox6::writeData(char * buffer, size_t len)
+int Ublox6::writeData(char * buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
diff --git a/src/ublox6/ublox6.h b/src/ublox6/ublox6.h
index f9ceef35..9eb57d7f 100644
--- a/src/ublox6/ublox6.h
+++ b/src/ublox6/ublox6.h
@@ -98,7 +98,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return the Number of bytes read
      */
-    int readData(char *buffer, size_t len);
+    int readData(char *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -107,7 +107,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. The default
diff --git a/src/upm.i b/src/upm.i
index f7d82ca6..37708673 100644
--- a/src/upm.i
+++ b/src/upm.i
@@ -4,9 +4,8 @@
 
 
 #if (SWIGJAVA)
-    /*    %include "arrays_java.i";*/
-    /*    %apply unsigned char[] {uint8_t *mama}; */
- 
+        /* %include "arrays_java.i"; */
+        /* %apply unsigned char[] {uint8_t *mama}; */
         %apply int { speed_t };
         %apply int { mraa_result_t };
         %apply int { mraa::Result };
@@ -32,3 +31,6 @@
 %}
 void cleanUp();
 #endif
+
+#if (SWIGJAVA)
+#endif
diff --git a/src/wt5001/javaupm_wt5001.i b/src/wt5001/javaupm_wt5001.i
index 7fabed2d..34753f95 100644
--- a/src/wt5001/javaupm_wt5001.i
+++ b/src/wt5001/javaupm_wt5001.i
@@ -2,6 +2,7 @@
 %include "../upm.i"
 %include "stdint.i"
 %include "typemaps.i"
+%include "../java_buffer.i"
 
 %apply uint8_t *OUTPUT { uint8_t *vol };
 %apply uint8_t *OUTPUT { uint8_t *ps };
diff --git a/src/wt5001/wt5001.cxx b/src/wt5001/wt5001.cxx
index c192521e..bbcf7597 100644
--- a/src/wt5001/wt5001.cxx
+++ b/src/wt5001/wt5001.cxx
@@ -91,7 +91,7 @@ bool WT5001::dataAvailable(unsigned int millis)
     return false;
 }
 
-int WT5001::readData(char *buffer, size_t len)
+int WT5001::readData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -107,7 +107,7 @@ int WT5001::readData(char *buffer, size_t len)
   return rv;
 }
 
-int WT5001::writeData(char *buffer, size_t len)
+int WT5001::writeData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
diff --git a/src/wt5001/wt5001.h b/src/wt5001/wt5001.h
index 35015c40..32b4c8f0 100644
--- a/src/wt5001/wt5001.h
+++ b/src/wt5001/wt5001.h
@@ -149,7 +149,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes read
      */
-    int readData(char *buffer, size_t len);
+    int readData(char *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -158,7 +158,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. The default
diff --git a/src/zfm20/javaupm_zfm20.i b/src/zfm20/javaupm_zfm20.i
index 1941d4af..b466dbe0 100644
--- a/src/zfm20/javaupm_zfm20.i
+++ b/src/zfm20/javaupm_zfm20.i
@@ -3,6 +3,7 @@
 %include "stdint.i"
 %include "typemaps.i"
 %include "arrays_java.i";
+%include "../java_buffer.i";
 
 %apply uint16_t *OUTPUT { uint16_t *id, uint16_t *score };
 
@@ -12,22 +13,5 @@
 %}
 
 
-%typemap(jni) (char *buffer, size_t len) "jbyteArray";
-%typemap(jtype) (char *buffer, size_t len) "byte[]";
-%typemap(jstype) (char *buffer, size_t len) "byte[]";
-
-%typemap(javain) (char *buffer, size_t len) "$javainput";
-
-%typemap(in) (char *buffer, size_t len) {
-        $1 = (char *) JCALL2(GetByteArrayElements, jenv, $input, NULL);
-        $2 = JCALL1(GetArrayLength, jenv, $input);
-}
-
-%typemap(freearg) (char *buffer, size_t len) {
-        JCALL3(ReleaseByteArrayElements, jenv, $input, (jbyte *)$1, 0);
-}
-
-%apply (char *buffer, size_t len) { (unsigned char *pkt, int len) };
-
 %include "zfm20.h"
 speed_t int_B57600 = B57600;
diff --git a/src/zfm20/zfm20.cxx b/src/zfm20/zfm20.cxx
index 1b5ee9ad..bf34071a 100644
--- a/src/zfm20/zfm20.cxx
+++ b/src/zfm20/zfm20.cxx
@@ -97,7 +97,7 @@ bool ZFM20::dataAvailable(unsigned int millis)
     return false;
 }
 
-int ZFM20::readData(char *buffer, size_t len)
+int ZFM20::readData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -113,7 +113,7 @@ int ZFM20::readData(char *buffer, size_t len)
   return rv;
 }
 
-int ZFM20::writeData(char *buffer, size_t len)
+int ZFM20::writeData(char *buffer, int len)
 {
   if (m_ttyFd == -1)
     return(-1);
@@ -162,9 +162,9 @@ bool ZFM20::setupTty(speed_t baud)
   return true;
 }
 
-int ZFM20::writeCmdPacket(unsigned char *pkt, int len)
+int ZFM20::writeCmdPacket(uint8_t *pkt, int len)
 {
-  unsigned char rPkt[ZFM20_MAX_PKT_LEN];
+  uint8_t rPkt[ZFM20_MAX_PKT_LEN];
 
   rPkt[0] = ZFM20_START1;             // header bytes
   rPkt[1] = ZFM20_START2;
@@ -229,7 +229,7 @@ uint32_t ZFM20::getMillis()
   return elapse;
 }
 
-bool ZFM20::verifyPacket(unsigned char *pkt, int len)
+bool ZFM20::verifyPacket(uint8_t *pkt, int len)
 {
   // verify packet header
   if (pkt[0] != ZFM20_START1 || pkt[1] != ZFM20_START2)
@@ -249,7 +249,7 @@ bool ZFM20::verifyPacket(unsigned char *pkt, int len)
   return true;
 }
 
-bool ZFM20::getResponse(unsigned char *pkt, int len)
+bool ZFM20::getResponse(uint8_t *pkt, int len)
 {
   char buf[ZFM20_MAX_PKT_LEN];
 
@@ -311,7 +311,7 @@ bool ZFM20::verifyPassword()
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -335,7 +335,7 @@ int ZFM20::getNumTemplates()
 
   // now read a response
   const int rPktLen = 14;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -371,7 +371,7 @@ bool ZFM20::setNewPassword(uint32_t pwd)
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -409,7 +409,7 @@ bool ZFM20::setNewAddress(uint32_t addr)
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -443,7 +443,7 @@ uint8_t ZFM20::generateImage()
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -474,7 +474,7 @@ uint8_t ZFM20::image2Tz(int slot)
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -498,7 +498,7 @@ uint8_t ZFM20::createModel()
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -531,7 +531,7 @@ uint8_t ZFM20::storeModel(int slot, uint16_t id)
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -559,7 +559,7 @@ uint8_t ZFM20::deleteModel(uint16_t id)
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -583,7 +583,7 @@ uint8_t ZFM20::deleteDB()
 
   // now read a response
   const int rPktLen = 12;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -622,7 +622,7 @@ uint8_t ZFM20::search(int slot, uint16_t *id, uint16_t *score)
 
   // now read a response
   const int rPktLen = 16;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
@@ -655,7 +655,7 @@ uint8_t ZFM20::match(uint16_t *score)
 
   // now read a response
   const int rPktLen = 14;
-  unsigned char rPkt[rPktLen];
+  uint8_t rPkt[rPktLen];
 
   if (!getResponse(rPkt, rPktLen))
     {
diff --git a/src/zfm20/zfm20.h b/src/zfm20/zfm20.h
index 6625e9d7..324c9ec4 100644
--- a/src/zfm20/zfm20.h
+++ b/src/zfm20/zfm20.h
@@ -179,7 +179,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes read
      */
-    int readData(char *buffer, size_t len);
+    int readData(char *buffer, int len);
 
     /**
      * Writes the data in the buffer to the device
@@ -188,7 +188,7 @@ namespace upm {
      * @param len Length of the buffer
      * @return Number of bytes written
      */
-    int writeData(char *buffer, size_t len);
+    int writeData(char *buffer, int len);
 
     /**
      * Sets up proper tty I/O modes and the baud rate. For this device,
@@ -206,7 +206,7 @@ namespace upm {
      * @param len Length of packet
      * @return Number of bytes written
      */
-    int writeCmdPacket(unsigned char *pkt, int len);
+    int writeCmdPacket(uint8_t *pkt, int len);
 
     /**
      * Verifies the packet header and indicates its validity
@@ -215,7 +215,7 @@ namespace upm {
      * @param len Length of packet
      * @return True if the packet is valid, false otherwise
      */
-    bool verifyPacket(unsigned char *pkt, int len);
+    bool verifyPacket(uint8_t *pkt, int len);
 
     /**
      * Returns the number of milliseconds elapsed since initClock()
@@ -253,7 +253,7 @@ namespace upm {
      * large
      * @return True if successful
      */
-    bool getResponse(unsigned char *pkt, int len);
+    bool getResponse(uint8_t *pkt, int len);
 
     /**
      * Verifies and authenticates to the module. The password used is