/* sla includes all 8 bits (with r/w bit), assums master transmit */
uint8_t u8g_i2c_start(uint8_t sla)
{
register uint8_t status;
/* send start */
TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);
/* wait */
if ( u8g_i2c_wait(_BV(TWINT), 1) == 0 )
return 0;
status = TW_STATUS;
/* check status after start */
if ( status != TW_START && status != TW_REP_START )
{
u8g_i2c_set_error(U8G_I2C_ERR_BUS, 1);
return 0;
}
/* set slave address */
TWDR = sla;
/* enable sla transfer */
TWCR = _BV(TWINT) | _BV(TWEN);
/* wait */
if ( u8g_i2c_wait(_BV(TWINT), 2) == 0 )
return 0;
if ( u8g_i2c_opt & U8G_I2C_OPT_NO_ACK )
{
/* do not check for ACK */
}
else
{
status = TW_STATUS;
/* check status after sla */
if ( status != TW_MT_SLA_ACK )
{
u8g_i2c_set_error(U8G_I2C_ERR_BUS, 2);
return 0;
}
}
return 1;
}
uint8_t u8g_i2c_wait(uint8_t mask, uint8_t pos)
{
volatile uint16_t cnt = 2000; /* timout value should be > 280 for 50KHz Bus and 16 Mhz CPU, however the start condition might need longer */
while( !(TWCR & mask) )
{
if ( cnt == 0 )
{
u8g_i2c_set_error(U8G_I2C_ERR_TIMEOUT, pos);
return 0; /* error */
}
cnt--;
}
return 1; /* all ok */
}
uint8_t u8g_i2c_send_byte(uint8_t data)
{
register uint8_t status;
TWDR = data;
TWCR = _BV(TWINT) | _BV(TWEN);
if ( u8g_i2c_wait(_BV(TWINT), 3) == 0 )
return 0;
status = TW_STATUS;
if ( status != TW_MT_DATA_ACK )
{
u8g_i2c_set_error(U8G_I2C_ERR_BUS, 3);
return 0;
}
return 1;
}
uint8_t u8g_i2c_send_byte(uint8_t data)
{
register uint8_t status;
TWDR = data;
TWCR = _BV(TWINT) | _BV(TWEN);
if ( u8g_i2c_wait(_BV(TWINT), 3) == 0 )
return 0;
if ( u8g_i2c_opt & U8G_I2C_OPT_NO_ACK )
{
/* do not check for ACK */
}
else
{
status = TW_STATUS;
if ( status != TW_MT_DATA_ACK )
{
u8g_i2c_set_error(U8G_I2C_ERR_BUS, 3);
return 0;
}
}
return 1;
}