;***************************************
;func: data = i2c_read(void) // always NAK
;***************************************
i2c_read:
	clc			; comment out this for ACK if .cs
	ldi	temp,(1<<TWINT)|(1<<TWEN)
	brcc	i2c_nak
	ori	temp,(1<<TWEA)
i2c_nak:
	STORE	TWCR,temp
	rcall	i2c_wait
	LOAD	data,TWDR
	ret
	
;***** internal function wait for TWI operation to complete ***
i2c_wait:
	LOAD	temp,TWCR	; use register cos sfr is out of range
	sbrs	temp,TWINT
	rjmp	i2c_wait
	ret

;****************************
;func: void I2C_Stop(void)
;****************************
I2C_Stop: 
	ldi	temp,(1<<TWINT)|(1<<TWEN)|(1<<TWSTO)
	STORE	TWCR,temp
stop_w:	LOAD	temp,TWCR	; wait for TWSTO to clear
	sbrc	temp,TWSTO
	rjmp	stop_w
	ret