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@@ -57,34 +57,52 @@ void twi_disable(void)
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digitalWrite(SCL, 0);
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}
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-uint8_t twi_waitfor(uint8_t status)
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+static void twi_wait()
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{
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while(!(TWCR & _BV(TWINT)));
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- return (TW_STATUS != status);
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}
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uint8_t twi_rw8(uint8_t address, uint8_t mode, uint8_t* data)
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{
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// send start condition
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TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWSTA);
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- if(twi_waitfor(TW_START))
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+ twi_wait();
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+ if(TW_STATUS != TW_START)
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return 1;
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// send address
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TWDR = mode;
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TWDR |= (address << 1);
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TWCR = _BV(TWEN) | _BV(TWINT);
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- if(twi_waitfor(mode == TW_READ? TW_MR_SLA_ACK: TW_MT_SLA_ACK))
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- return 2;
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+ twi_wait();
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- // send or receive data
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if(mode == TW_WRITE)
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+ {
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+ if(TW_STATUS != TW_MT_SLA_ACK)
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+ return 2;
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+
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+ // send data
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TWDR = *data;
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- TWCR = _BV(TWEN) | _BV(TWINT);
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- if(twi_waitfor(mode == TW_READ? TW_MR_DATA_NACK: TW_MT_DATA_ACK))
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- return 3;
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- if(mode == TW_READ)
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+ TWCR = _BV(TWEN) | _BV(TWINT);
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+ twi_wait();
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+ if(TW_STATUS != TW_MT_DATA_ACK)
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+ return 3;
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+ }
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+ else
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+ {
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+ if(TW_STATUS != TW_MR_SLA_ACK)
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+ return 2;
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+
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+ // receive data
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+ TWCR = _BV(TWEN) | _BV(TWINT);
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+ twi_wait();
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+
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+ // accept ACK or NACK (since only 1 byte is read)
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+ if(!(TW_STATUS & TW_MR_DATA_ACK))
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+ return 3;
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+
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*data = TWDR;
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+ }
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// send stop
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TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWSTO);
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