diff --git a/.gitmodules b/.gitmodules
index c71a746..a89dd6c 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -13,3 +13,6 @@
 [submodule "ds3231/type"]
 	path = ds3231/type
 	url = git@git.blackmark.me:avr/type.git
+[submodule "ds3231/i2c"]
+	path = ds3231/i2c
+	url = git@git.blackmark.me:avr/i2c.git
diff --git a/ds3231/ds3231 b/ds3231/ds3231
index 04af54e..2768009 160000
--- a/ds3231/ds3231
+++ b/ds3231/ds3231
@@ -1 +1 @@
-Subproject commit 04af54e7c8029f05a999f85afa0bcc194f654fed
+Subproject commit 27680097203f1482ba61a9cceef689305d7eadc4
diff --git a/ds3231/ds3231.cppproj b/ds3231/ds3231.cppproj
index 0b055a6..9715776 100644
--- a/ds3231/ds3231.cppproj
+++ b/ds3231/ds3231.cppproj
@@ -83,6 +83,17 @@
     </custom>
     <AAFDebugger>
       <AAFDebugFiles>
+        <DebugFile>
+          <path>\Debug\ds3231.lss</path>
+          <AAFSetting>
+            <Label>Lss Files</Label>
+            <Extention>.lss</Extention>
+            <Regex>^\s*(?&lt;address&gt;[a-f0-9]*):\s*.*$</Regex>
+            <DebugEnabled>true</DebugEnabled>
+            <RegexGroups>address</RegexGroups>
+            <DebuggerExpression>$pc</DebuggerExpression>
+          </AAFSetting>
+        </DebugFile>
       </AAFDebugFiles>
     </AAFDebugger>
   </PropertyGroup>
@@ -213,21 +224,15 @@
     <Compile Include="ds3231\rtc.h">
       <SubType>compile</SubType>
     </Compile>
-    <Compile Include="ds3231\twi-lowlevel.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="ds3231\twi-lowlevel.h">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="ds3231\twi.cpp">
-      <SubType>compile</SubType>
-    </Compile>
-    <Compile Include="ds3231\twi.h">
-      <SubType>compile</SubType>
-    </Compile>
     <Compile Include="flash\flash.hpp">
       <SubType>compile</SubType>
     </Compile>
+    <Compile Include="i2c\hardware.hpp">
+      <SubType>compile</SubType>
+    </Compile>
+    <Compile Include="i2c\i2c.hpp">
+      <SubType>compile</SubType>
+    </Compile>
     <Compile Include="io\io.hpp">
       <SubType>compile</SubType>
     </Compile>
@@ -266,6 +271,7 @@
     <Folder Include="ds3231" />
     <Folder Include="io" />
     <Folder Include="flash" />
+    <Folder Include="i2c" />
     <Folder Include="uart" />
     <Folder Include="type" />
   </ItemGroup>
diff --git a/ds3231/i2c b/ds3231/i2c
new file mode 160000
index 0000000..ff131d9
--- /dev/null
+++ b/ds3231/i2c
@@ -0,0 +1 @@
+Subproject commit ff131d92a1b8e92efc2ae24306d7b7cac3cfb28a
diff --git a/ds3231/main.cpp b/ds3231/main.cpp
index b2e7da5..7301d90 100644
--- a/ds3231/main.cpp
+++ b/ds3231/main.cpp
@@ -1,14 +1,16 @@
 #include "clock.hpp"
 
-#include <avr/interrupt.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
 
-#include "systime.h"
+#include <avr/interrupt.h>
+
 #include "uart/uart.hpp"
 
+#include "systime.h"
+
 using uart_t = uart::Uart0<>;
 
 REGISTER_UART0_INT_VECTORS(uart_t);
diff --git a/ds3231/systime.cpp b/ds3231/systime.cpp
index 315f255..4f79579 100644
--- a/ds3231/systime.cpp
+++ b/ds3231/systime.cpp
@@ -22,7 +22,6 @@ int SysTime::euDST( const time_t *pTime, int32_t *pZ )
 //////////////////////////////////////////////////////////////////////////
 bool SysTime::init()
 {
-	twi_init_master();
 	rtc_init();
 
 	if( !rtc_is_ds3231() )
@@ -104,4 +103,4 @@ void SysTime::setTime( const tm &sTime )
 	rtc_set_time( pRtcTime );
 
 	syncSysTime();
-}
\ No newline at end of file
+}
diff --git a/ds3231/systime.h b/ds3231/systime.h
index af8e0bc..d7c4d7a 100644
--- a/ds3231/systime.h
+++ b/ds3231/systime.h
@@ -9,7 +9,6 @@
 
 #include <time.h>
 
-#include "ds3231/twi.h"
 #include "ds3231/rtc.h"
 
 class SysTime