From 5e0fd7741125d4c933127ecf31d0a98a930e121c Mon Sep 17 00:00:00 2001
From: Dan Nixon <dan@dan-nixon.com>
Date: Sat, 1 Feb 2014 21:29:44 +0000
Subject: [PATCH 1/2] Added TWI max iteration timeout to while loops

---
 libraries/Wire/utility/twi.c | 34 +++++++++++++++++++++++++++++-----
 libraries/Wire/utility/twi.h |  3 +++
 2 files changed, 32 insertions(+), 5 deletions(-)
 mode change 100755 => 100644 libraries/Wire/utility/twi.h

diff --git a/libraries/Wire/utility/twi.c b/libraries/Wire/utility/twi.c
index 201d7d1bbbf..a16829213a5 100644
--- a/libraries/Wire/utility/twi.c
+++ b/libraries/Wire/utility/twi.c
@@ -59,6 +59,8 @@ static volatile uint8_t twi_rxBufferIndex;
 
 static volatile uint8_t twi_error;
 
+volatile uint32_t twi_tog_count;
+
 /* 
  * Function twi_init
  * Desc     readys twi pins and sets twi bitrate
@@ -122,7 +124,8 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen
   }
 
   // wait until twi is ready, become master receiver
-  while(TWI_READY != twi_state){
+  twi_timeout_guard(1);
+  while((TWI_READY != twi_state) && !twi_timeout_guard(0)){
     continue;
   }
   twi_state = TWI_MRX;
@@ -159,7 +162,8 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sen
     TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
 
   // wait for read operation to complete
-  while(TWI_MRX == twi_state){
+  twi_timeout_guard(1);
+  while((TWI_MRX == twi_state) && !twi_timeout_guard(0)){
     continue;
   }
 
@@ -199,7 +203,8 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait
   }
 
   // wait until twi is ready, become master transmitter
-  while(TWI_READY != twi_state){
+  twi_timeout_guard(1);
+  while((TWI_READY != twi_state) && !twi_timeout_guard(0)){
     continue;
   }
   twi_state = TWI_MTX;
@@ -239,7 +244,8 @@ uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait
     TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA);	// enable INTs
 
   // wait for write operation to complete
-  while(wait && (TWI_MTX == twi_state)){
+  twi_timeout_guard(1);
+  while((wait && (TWI_MTX == twi_state)) && !twi_timeout_guard(0)){
     continue;
   }
   
@@ -337,7 +343,8 @@ void twi_stop(void)
 
   // wait for stop condition to be exectued on bus
   // TWINT is not set after a stop condition!
-  while(TWCR & _BV(TWSTO)){
+  twi_timeout_guard(1);
+  while((TWCR & _BV(TWSTO)) && !twi_timeout_guard(0)){
     continue;
   }
 
@@ -525,3 +532,20 @@ ISR(TWI_vect)
   }
 }
 
+uint8_t twi_timeout_guard(uint8_t init)
+{
+  if(init)
+    twi_tog_count = 0;
+  else
+  {
+    twi_tog_count++;
+    if(twi_tog_count > TWI_MAX_ITERS)
+    {
+      twi_init();
+      TWCR = 0;
+      return 1;
+    }
+  }
+  return 0;
+}
+
diff --git a/libraries/Wire/utility/twi.h b/libraries/Wire/utility/twi.h
old mode 100755
new mode 100644
index 6526593394e..8b8699ffbf1
--- a/libraries/Wire/utility/twi.h
+++ b/libraries/Wire/utility/twi.h
@@ -37,6 +37,8 @@
   #define TWI_MTX   2
   #define TWI_SRX   3
   #define TWI_STX   4
+
+  #define TWI_MAX_ITERS 100000UL
   
   void twi_init(void);
   void twi_setAddress(uint8_t);
@@ -48,6 +50,7 @@
   void twi_reply(uint8_t);
   void twi_stop(void);
   void twi_releaseBus(void);
+  uint8_t twi_timeout_guard(uint8_t);
 
 #endif
 

From 6169a08763e6f00d0f17293ac60aacbf3061f3d6 Mon Sep 17 00:00:00 2001
From: Dan Nixon <dan@dan-nixon.com>
Date: Sat, 1 Feb 2014 21:33:06 +0000
Subject: [PATCH 2/2] Refactoring

---
 libraries/Wire/utility/twi.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libraries/Wire/utility/twi.c b/libraries/Wire/utility/twi.c
index a16829213a5..94e2df191f4 100644
--- a/libraries/Wire/utility/twi.c
+++ b/libraries/Wire/utility/twi.c
@@ -59,7 +59,7 @@ static volatile uint8_t twi_rxBufferIndex;
 
 static volatile uint8_t twi_error;
 
-volatile uint32_t twi_tog_count;
+volatile uint32_t twi_iter_count;
 
 /* 
  * Function twi_init
@@ -535,11 +535,11 @@ ISR(TWI_vect)
 uint8_t twi_timeout_guard(uint8_t init)
 {
   if(init)
-    twi_tog_count = 0;
+    twi_iter_count = 0;
   else
   {
-    twi_tog_count++;
-    if(twi_tog_count > TWI_MAX_ITERS)
+    twi_iter_count++;
+    if(twi_iter_count > TWI_MAX_ITERS)
     {
       twi_init();
       TWCR = 0;