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

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Fixed TWI_StartTransmission() corrupting the contents of the GPIOR0 register.
This commit is contained in:
Dean Camera
2010-02-24 09:49:19 +00:00
parent 14a5a94084
commit c0c982df7a
6 changed files with 56 additions and 30 deletions
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4
LUFA/Drivers/Peripheral/AVRU4U6U7/TWI.h
View File

@@ -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)

61
LUFA/Drivers/Peripheral/TWI.c
View File

@@ -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;
}
}
}
}