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.

2 files changed, 43 insertions, 22 deletions

diff --git a/LUFA/Drivers/Peripheral/AVRU4U6U7/TWI.h b/LUFA/Drivers/Peripheral/AVRU4U6U7/TWI.h
index 13db86e69..2d8e6df1e 100644
--- a/LUFA/Drivers/Peripheral/AVRU4U6U7/TWI.h
+++ b/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)

diff --git a/LUFA/Drivers/Peripheral/TWI.c b/LUFA/Drivers/Peripheral/TWI.c
index 6028bbae9..eb513c454 100644
--- a/LUFA/Drivers/Peripheral/TWI.c
+++ b/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;

-		}		  

+		}

 	}

 }