Added a timeout value to the TWI_StartTransmission() function, within which the addressed device must respond.

Fixed TWI_StartTransmission() corrupting the contents of the GPIOR0 register.

LUFA/Drivers/Peripheral/AVRU4U6U7/TWI.h

@@ -56,6 +56,7 @@
 		#include <avr/io.h>
 		#include <stdbool.h>
 		#include <util/twi.h>
+		#include <util/delay.h>
 		
 	/* Enable C linkage for C++ Compilers: */
 		#if defined(__cplusplus)
@@ -131,10 +132,11 @@
 			/** Begins a master mode TWI bus communication with the given slave device address.
 			 *
 			 *  \param[in] SlaveAddress  Address of the slave TWI device to communicate with
+			 *  \param[in] TimeoutMS     Timeout period within which the slave must respond, in milliseconds
 			 *
 			 *  \return Boolean true if the device is ready for data, false otherwise
 			 */
-			bool TWI_StartTransmission(uint8_t SlaveAddress);
+			bool TWI_StartTransmission(uint8_t SlaveAddress, uint8_t TimeoutMS);
 
 	/* Disable C linkage for C++ Compilers: */
 		#if defined(__cplusplus)

LUFA/Drivers/Peripheral/TWI.c

@@ -7,39 +7,58 @@
 
 #include "TWI.h"
 
-bool TWI_StartTransmission(uint8_t SlaveAddress)
+bool TWI_StartTransmission(uint8_t SlaveAddress, uint8_t TimeoutMS)
 {
 	for (;;)
 	{
-		uint8_t IterationsRemaining = 50;
-		bool    BusCaptured = false;
+		bool     BusCaptured = false;
+		uint16_t TimeoutRemaining;
 
-		while (IterationsRemaining-- && !BusCaptured)
+		TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));	
+
+		TimeoutRemaining = (TimeoutMS * 100);
+		while (TimeoutRemaining-- && !BusCaptured)
 		{
-			TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));	
-			while (!(TWCR & (1 << TWINT)));
-				
-			switch (TWSR & TW_STATUS_MASK)
+			if (TWCR & (1 << TWINT))
 			{
-				case TW_START:
-				case TW_REP_START:
-					BusCaptured = true;
-					break;
-				case TW_MT_ARB_LOST:
-					continue;
-				default:
-					return false;
+				switch (TWSR & TW_STATUS_MASK)
+				{
+					case TW_START:
+					case TW_REP_START:
+						BusCaptured = true;
+						break;
+					case TW_MT_ARB_LOST:
+						TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));	
+						continue;
+					default:
+						TWCR = (1 << TWEN);
+						return false;
+				}
 			}
+			
+			_delay_us(10);
 		}
 		
 		if (!(BusCaptured))
-		  return false;
-		  
+		{
+			TWCR = (1 << TWEN);
+			return false;
+		}
+		
 		TWDR = SlaveAddress;
 		TWCR = ((1 << TWINT) | (1 << TWEN));
-		while (!(TWCR & (1 << TWINT)));
 		
-		GPIOR0 = (TWSR & TW_STATUS_MASK);
+		TimeoutRemaining = (TimeoutMS * 100);
+		while (TimeoutRemaining--)
+		{
+			if (TWCR & (1 << TWINT))
+			  break;
+			  
+			_delay_us(10);
+		}
+		
+		if (!(TimeoutRemaining))
+		  return false;
 
 		switch (TWSR & TW_STATUS_MASK)
 		{
@@ -49,6 +68,6 @@ bool TWI_StartTransmission(uint8_t SlaveAddress)
 			default:
 				TWI_StopTransmission();
 				break;
-		}		  
+		}
 	}
 }

LUFA/ManPages/ChangeLog.txt

@@ -15,9 +15,11 @@
   *  - AVRISP programmer project now has a more robust timeout system, allowing for a doubling of the software USART speed
   *    for PDI and TPI programming
   *  - Increased the speed of both software and hardware TPI/PDI programming modes of the AVRISP project
+  *  - Added a timeout value to the TWI_StartTransmission() function, within which the addressed device must respond
   *
   *  <b>Fixed:</b>
   *  - Fixed software PDI/TPI programming mode in the AVRISP project not correctly toggling just the clock pin
+  *  - Fixed TWI_StartTransmission() corrupting the contents of the GPIOR0 register
   *
   *  \section Sec_ChangeLog100219 Version 100219
   *

LUFA/ManPages/MigrationInformation.txt

@@ -12,8 +12,11 @@
  *
  * \section Sec_MigrationXXXXXX Migrating from 100219 to XXXXXX
  *
+ *  <b>Non-USB Library Components</b>
+ *    - The \ref TWI_StartTransmission() function now takes in a timeout period, expressed in milliseconds, within which the addressed
+ *      device must respond or the function will abort.
+ *
  * \section Sec_Migration100219 Migrating from 091223 to 100219
- *    - (None)
  *
  *  <b>Non-USB Library Components</b>
  *    - Due to some ADC channels not being identical to their ADC MUX selection masks for single-ended conversions on some AVR models,