i2c-test.c - test correctness of I2C controller block. Use voltage meter to
	check if SDA/SCL on both PCFs goes up/down as the test program sets
	them up/down. Check if read values are same as set values.

	SDA high - set:
		LPT pin 9 should be low
		LPT pin 11 should be low
		pins 1 and 4 on 74LS05 should be high
	SDA low gives opposite values (i.e. high instead of low,
		low instead of high)

	SCL high - set:
		LPT pin 17 should be low
		LPT pin 15 should be high
		pins 6 and 9 on 74LS05 should be high
		pins 8 and 11 on 74LS05 should be low
	SCL low gives opposite values.