- // reset TWI control register
- TWCR = 0;
- // transmit START condition
- TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
- // wait for end of transmission
- while( !(TWCR & (1<<TWINT)) );
-
- // check if the start condition was successfully transmitted
- if((TWSR & 0xF8) != TW_START){ return 1; }
-
- // load slave address into data register
- TWDR = address;
- // start transmission of address
- TWCR = (1<<TWINT) | (1<<TWEN);
- // wait for end of transmission
- while( !(TWCR & (1<<TWINT)) );
-
- // check if the device has acknowledged the READ / WRITE mode
- uint8_t twst = TW_STATUS & 0xF8;
- if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;
-
- return 0;
+ // reset TWI control register
+ TWCR = 0;
+ // transmit START condition
+ TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
+
+ uint16_t timeout_timer = timer_read();
+ while( !(TWCR & (1<<TWINT)) ) {
+ if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
+ return I2C_STATUS_TIMEOUT;
+ }
+ }
+
+ // check if the start condition was successfully transmitted
+ if(((TW_STATUS & 0xF8) != TW_START) && ((TW_STATUS & 0xF8) != TW_REP_START)){ return I2C_STATUS_ERROR; }
+
+ // load slave address into data register
+ TWDR = address;
+ // start transmission of address
+ TWCR = (1<<TWINT) | (1<<TWEN);
+
+ timeout_timer = timer_read();
+ while( !(TWCR & (1<<TWINT)) ) {
+ if ((timeout != I2C_TIMEOUT_INFINITE) && ((timer_read() - timeout_timer) >= timeout)) {
+ return I2C_STATUS_TIMEOUT;
+ }
+ }
+
+ // check if the device has acknowledged the READ / WRITE mode
+ uint8_t twst = TW_STATUS & 0xF8;
+ if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return I2C_STATUS_ERROR;
+
+ return I2C_STATUS_SUCCESS;