//
// Send a START Condition
//
// The SDA and SCL should already be high.
//
// The SDA and SCL will both be low after this function.
// When writing the address, the Master makes them high.
//
// Return value:
// true : software i2c bus is okay.
// false : failed, some kind of hardware bus error.
//
boolean SoftwareWire::i2c_start(void)
{
i2c_sda_hi(); // can perhaps be removed some day ? if the rest of the code is okay
i2c_scl_hi(); // can perhaps be removed some day ? if the rest of the code is okay
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
// Both the sda and scl should be high.
// If not, there might be a hardware problem with the i2c bus signal lines.
// This check was added to prevent that a shortcut of sda would be seen as a valid ACK
// from a i2c Slave.
uint8_t sda_status = i2c_sda_read();
uint8_t scl_status = i2c_scl_read();
if(sda_status == 0 || scl_status == 0)
{
return(false);
}
else
{
i2c_sda_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_scl_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
}
return(true);
}
uint8_t SoftwareWire::i2c_readbit(void)
{
i2c_sda_hi(); // 'hi' is the same as releasing the line
i2c_scl_hi();
// Check if clock stretching by the Slave should be detected.
if( _stretch)
{
// Wait until the clock is high, the Slave could keep it low for clock stretching.
unsigned long prevMillis = millis();
while( i2c_scl_read() == 0)
{
if( millis() - prevMillis >= _timeout)
break;
};
}
// After the clock stretching, this delay has still be done before reading sda.
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
uint8_t c = i2c_sda_read();
i2c_scl_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
return(c);
}
uint8_t SoftI2CMaster::i2c_readbit(void)
{
i2c_sda_hi();
i2c_scl_hi();
_delay_us(i2cbitdelay);
uint8_t port = digitalPinToPort(_sdaPin);
volatile uint8_t* pinReg = portInputRegister(port);
uint8_t c = *pinReg; // I2C_PIN;
i2c_scl_lo();
_delay_us(i2cbitdelay);
return ( c & _sdaBitMask) ? 1 : 0;
}
// Send a START Condition
//
void SoftI2CMaster::i2c_start(void)
{
// set both to high at the same time
//I2C_DDR &=~ (_BV( I2C_SDA ) | _BV( I2C_SCL ));
//*_sclDirReg &=~ (_sdaBitMask | _sclBitMask);
i2c_sda_hi();
i2c_scl_hi();
_delay_us(i2cbitdelay);
i2c_sda_lo();
_delay_us(i2cbitdelay);
i2c_scl_lo();
_delay_us(i2cbitdelay);
}
void SoftI2CMaster::i2c_writebit( uint8_t c )
{
if ( c > 0 ) {
i2c_sda_hi();
} else {
i2c_sda_lo();
}
i2c_scl_hi();
_delay_us(i2cbitdelay);
i2c_scl_lo();
_delay_us(i2cbitdelay);
if ( c > 0 ) {
i2c_sda_lo();
}
_delay_us(i2cbitdelay);
}
void SoftI2CMaster::i2c_repstart(void)
{
// set both to high at the same time (releases drive on both lines)
//I2C_DDR &=~ (_BV( I2C_SDA ) | _BV( I2C_SCL ));
//*_sclDirReg &=~ (_sdaBitMask | _sclBitMask);
i2c_sda_hi();
i2c_scl_hi();
i2c_scl_lo(); // force SCL low
_delay_us(i2cbitdelay);
i2c_sda_release(); // release SDA
_delay_us(i2cbitdelay);
i2c_scl_release(); // release SCL
_delay_us(i2cbitdelay);
i2c_sda_lo(); // force SDA low
_delay_us(i2cbitdelay);
}
//
// The i2c_writebit and i2c_readbit could be make "inline", but that
// didn't increase the speed, and the code size increases.
//
// The sda is low after the start condition.
// Therefor the sda is low for the first bit.
//
void SoftwareWire::i2c_writebit(uint8_t c)
{
if(c==0)
{
i2c_sda_lo();
}
else
{
i2c_sda_hi();
}
if (_i2cdelay != 0) // This delay is not needed, but it makes it safer
delayMicroseconds(_i2cdelay); // This delay is not needed, but it makes it safer
i2c_scl_hi(); // clock high: the Slave will read the sda signal
// Check if clock stretching by the Slave should be detected.
if( _stretch)
{
// If the Slave was strechting the clock pulse, the clock would not go high immediately.
// For example if the Slave is an Arduino, that has other interrupts running (for example Serial data).
unsigned long prevMillis = millis();
while( i2c_scl_read() == 0)
{
if( millis() - prevMillis >= _timeout)
break;
};
}
// After the clock stretching, the clock must be high for the normal duration.
// That is why this delay has still to be done.
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_scl_lo();
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
}
//
// Repeated START instead of a STOP
//
// TODO: check if the repeated start actually works.
//
void SoftwareWire::i2c_repstart(void)
{
i2c_sda_hi();
// i2c_scl_hi(); // ??????
i2c_scl_lo(); // force SCL low
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_sda_hi(); // release SDA
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_scl_hi(); // release SCL
// Check if clock stretching by the Slave should be detected.
if( _stretch)
{
// If the Slave was strechting the clock pulse, the clock would not go high immediately.
// For example if the Slave is an Arduino, that has other interrupts running (for example Serial data).
unsigned long prevMillis = millis();
while( i2c_scl_read() == 0)
{
if( millis() - prevMillis >= _timeout)
break;
};
}
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
i2c_sda_lo(); // force SDA low
if (_i2cdelay != 0)
delayMicroseconds(_i2cdelay);
}
