diff --git a/avr/libraries/Wire/src/Wire.cpp b/avr/libraries/Wire/src/Wire.cpp
index 6c1e48c74..3dcdeb148 100755
--- a/avr/libraries/Wire/src/Wire.cpp
+++ b/avr/libraries/Wire/src/Wire.cpp
@@ -17,6 +17,7 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  
   Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts
+  Modified 2017 by Chuck Todd (ctodd@cableone.net) to correct Unconfigured Slave Mode reboot
 */
 
 extern "C" {
@@ -60,14 +61,16 @@ void TwoWire::begin(void)
   txBufferLength = 0;
 
   twi_init();
+  twi_attachSlaveTxEvent(onRequestService); // default callback must exist
+  twi_attachSlaveRxEvent(onReceiveService); // default callback must exist
 }
 
 void TwoWire::begin(uint8_t address)
 {
-  twi_setAddress(address);
+  begin();
   twi_attachSlaveTxEvent(onRequestService);
   twi_attachSlaveRxEvent(onReceiveService);
-  begin();
+  twi_setAddress(address);
 }
 
 void TwoWire::begin(int address)
@@ -80,9 +83,9 @@ void TwoWire::end(void)
   twi_disable();
 }
 
-void TwoWire::setClock(uint32_t frequency)
+void TwoWire::setClock(uint32_t clock)
 {
-  TWBR = ((F_CPU / frequency) - 16) / 2;
+  twi_setFrequency(clock);
 }
 
 uint8_t TwoWire::requestFrom(uint8_t address, uint8_t quantity, uint32_t iaddress, uint8_t isize, uint8_t sendStop)
diff --git a/avr/libraries/Wire/src/utility/twi.c b/avr/libraries/Wire/src/utility/twi.c
index 8a674c654..6882a3d2c 100755
--- a/avr/libraries/Wire/src/utility/twi.c
+++ b/avr/libraries/Wire/src/utility/twi.c
@@ -118,6 +118,22 @@ void twi_setAddress(uint8_t address)
   TWAR = address << 1;
 }
 
+/*
+ * Function twi_setFrequency
+ * Desc     sets twi bit rate
+ * Input    Clock frequency
+ * Output   none
+ */
+void twi_setFrequency(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+
+  /* twi bit rate formula from atmega128 manual pg 204
+  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
+  note: TWBR should be 10 or higher for master mode
+  It is 72 for a 16mhz Wiring board with 100kHz TWI */
+}
+
 /* 
  * Function twi_readFrom
  * Desc     attempts to become twi bus master and read a
@@ -288,7 +304,7 @@ uint8_t twi_transmit(const uint8_t* data, uint8_t length)
   uint8_t i;
 
   // ensure data will fit into buffer
-  if(TWI_BUFFER_SIZE < length){
+  if(TWI_BUFFER_SIZE < (twi_txBufferLength+length)){
     return 1;
   }
   
@@ -300,9 +316,10 @@ uint8_t twi_transmit(const uint8_t* data, uint8_t length)
   // set length and copy data into tx buffer
   twi_txBufferLength = length;
   for(i = 0; i < length; ++i){
-    twi_txBuffer[i] = data[i];
+    twi_txBuffer[twi_txBufferLength+i] = data[i];
   }
-  
+  twi_txBufferLength += length;
+
   return 0;
 }
 
@@ -429,6 +446,7 @@ ISR(TWI_vect)
     case TW_MR_DATA_ACK: // data received, ack sent
       // put byte into buffer
       twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
+      __attribute__ ((fallthrough));
     case TW_MR_SLA_ACK:  // address sent, ack received
       // ack if more bytes are expected, otherwise nack
       if(twi_masterBufferIndex < twi_masterBufferLength){
@@ -515,6 +533,7 @@ ISR(TWI_vect)
         twi_txBuffer[0] = 0x00;
       }
       // transmit first byte from buffer, fall
+      __attribute__ ((fallthrough));
     case TW_ST_DATA_ACK: // byte sent, ack returned
       // copy data to output register
       TWDR = twi_txBuffer[twi_txBufferIndex++];
@@ -542,4 +561,3 @@ ISR(TWI_vect)
       break;
   }
 }
-
diff --git a/avr/libraries/Wire/src/utility/twi.h b/avr/libraries/Wire/src/utility/twi.h
index 62d97c068..b836d9f71 100755
--- a/avr/libraries/Wire/src/utility/twi.h
+++ b/avr/libraries/Wire/src/utility/twi.h
@@ -22,15 +22,12 @@
 
   #include <inttypes.h>
 
-  //#define ATMEGA8
-
   #ifndef TWI_FREQ
   #define TWI_FREQ 100000L
   #endif
 
   #ifndef TWI_BUFFER_SIZE
   #define TWI_BUFFER_SIZE 32
-  #define BUFFER_LENGTH TWI_BUFFER_SIZE // For backwards compatibility
   #endif
 
   #define TWI_READY 0
@@ -42,6 +39,7 @@
   void twi_init(void);
   void twi_disable(void);
   void twi_setAddress(uint8_t);
+  void twi_setFrequency(uint32_t);
   uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t, uint8_t);
   uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t);
   uint8_t twi_transmit(const uint8_t*, uint8_t);
diff --git a/avr/libraries/Wire1/keywords.txt b/avr/libraries/Wire1/keywords.txt
index 47ffd52d0..a5c1e7f75 100755
--- a/avr/libraries/Wire1/keywords.txt
+++ b/avr/libraries/Wire1/keywords.txt
@@ -22,7 +22,6 @@ onRequest	KEYWORD2
 # Instances (KEYWORD2)
 #######################################
 
-Wire	KEYWORD2
 Wire1	KEYWORD2
 
 #######################################
diff --git a/avr/libraries/Wire1/src/Wire1.cpp b/avr/libraries/Wire1/src/Wire1.cpp
index 74df6114c..41db40190 100755
--- a/avr/libraries/Wire1/src/Wire1.cpp
+++ b/avr/libraries/Wire1/src/Wire1.cpp
@@ -17,6 +17,7 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  
   Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts
+  Modified 2017 by Chuck Todd (ctodd@cableone.net) to correct Unconfigured Slave Mode reboot
 */
 
 extern "C" {
@@ -60,14 +61,16 @@ void TwoWire1::begin(void)
   txBufferLength = 0;
 
   twi_init1();
+  twi_attachSlaveTxEvent1(onRequestService); // default callback must exist
+  twi_attachSlaveRxEvent1(onReceiveService); // default callback must exist
 }
 
 void TwoWire1::begin(uint8_t address)
 {
-  twi_setAddress1(address);
+  begin();
   twi_attachSlaveTxEvent1(onRequestService);
   twi_attachSlaveRxEvent1(onReceiveService);
-  begin();
+  twi_setAddress1(address);
 }
 
 void TwoWire1::begin(int address)
@@ -80,9 +83,9 @@ void TwoWire1::end(void)
   twi_disable1();
 }
 
-void TwoWire1::setClock(uint32_t frequency)
+void TwoWire1::setClock(uint32_t clock)
 {
-  TWBR1 = ((F_CPU / frequency) - 16) / 2;
+  twi_setFrequency1(clock);
 }
 
 uint8_t TwoWire1::requestFrom(uint8_t address, uint8_t quantity, uint32_t iaddress, uint8_t isize, uint8_t sendStop)
diff --git a/avr/libraries/Wire1/src/utility/twi1.c b/avr/libraries/Wire1/src/utility/twi1.c
index 8be7de815..4929ad627 100755
--- a/avr/libraries/Wire1/src/utility/twi1.c
+++ b/avr/libraries/Wire1/src/utility/twi1.c
@@ -90,7 +90,7 @@ void twi_init1(void)
   TWCR1 = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
 }
 
-/* 
+/*
  * Function twi_disable
  * Desc     disables twi pins
  * Input    none
@@ -106,7 +106,7 @@ void twi_disable1(void)
   digitalWrite(SCL, 0);
 }
 
-/* 
+/*
  * Function twi_slaveInit
  * Desc     sets slave address and enables interrupt
  * Input    none
@@ -118,6 +118,22 @@ void twi_setAddress1(uint8_t address)
   TWAR1 = address << 1;
 }
 
+/*
+ * Function twi_setFrequency
+ * Desc     sets twi bit rate
+ * Input    Clock frequency
+ * Output   none
+ */
+void twi_setFrequency1(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+
+  /* twi bit rate formula from atmega128 manual pg 204
+  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR1))
+  note: TWBR1 should be 10 or higher for master mode
+  It is 72 for a 16mhz Wiring board with 100kHz TWI */
+}
+
 /* 
  * Function twi_readFrom
  * Desc     attempts to become twi bus master and read a
@@ -288,7 +304,7 @@ uint8_t twi_transmit1(const uint8_t* data, uint8_t length)
   uint8_t i;
 
   // ensure data will fit into buffer
-  if(TWI1_BUFFER_SIZE < length){
+  if(TWI1_BUFFER_SIZE < (twi_txBufferLength+length)){
     return 1;
   }
   
@@ -300,8 +316,9 @@ uint8_t twi_transmit1(const uint8_t* data, uint8_t length)
   // set length and copy data into tx buffer
   twi_txBufferLength = length;
   for(i = 0; i < length; ++i){
-    twi_txBuffer[i] = data[i];
+    twi_txBuffer[twi_txBufferLength+i] = data[i];
   }
+  twi_txBufferLength += length;
   
   return 0;
 }
@@ -430,6 +447,7 @@ ISR(TWI1_vect)
     case TW_MR_DATA_ACK: // data received, ack sent
       // put byte into buffer
       twi_masterBuffer[twi_masterBufferIndex++] = TWDR1;
+      __attribute__ ((fallthrough));
     case TW_MR_SLA_ACK:  // address sent, ack received
       // ack if more bytes are expected, otherwise nack
       if(twi_masterBufferIndex < twi_masterBufferLength){
@@ -516,6 +534,7 @@ ISR(TWI1_vect)
         twi_txBuffer[0] = 0x00;
       }
       // transmit first byte from buffer, fall
+      __attribute__ ((fallthrough));
     case TW_ST_DATA_ACK: // byte sent, ack returned
       // copy data to output register
       TWDR1 = twi_txBuffer[twi_txBufferIndex++];
diff --git a/avr/libraries/Wire1/src/utility/twi1.h b/avr/libraries/Wire1/src/utility/twi1.h
index eabbea0be..a62709e35 100755
--- a/avr/libraries/Wire1/src/utility/twi1.h
+++ b/avr/libraries/Wire1/src/utility/twi1.h
@@ -22,15 +22,12 @@
 
   #include <inttypes.h>
 
-  //#define ATMEGA8
-
   #ifndef TWI_FREQ
   #define TWI_FREQ 100000L
   #endif
 
   #ifndef TWI1_BUFFER_SIZE
   #define TWI1_BUFFER_SIZE 32
-  #define BUFFER_LENGTH1 TWI1_BUFFER_SIZE // For backwards compatibility
   #endif
 
   #define TWI_READY 0
@@ -42,6 +39,7 @@
   void twi_init1(void);
   void twi_disable1(void);
   void twi_setAddress1(uint8_t);
+  void twi_setFrequency1(uint32_t);
   uint8_t twi_readFrom1(uint8_t, uint8_t*, uint8_t, uint8_t);
   uint8_t twi_writeTo1(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t);
   uint8_t twi_transmit1(const uint8_t*, uint8_t);