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.