The main components of Optii are the bi-directional I2C transducer, the transducer for the test pins an the internal power supply as shown in Figure 1.

Figure 1 Schematic Diagram

Optii uses different low-voltages to code and detect activities on the I2C lines. An internal reference voltage, called Uref, defines the threshold for this decision. While Optii’s own low-signal remains a voltage (Ulow) slightly higher than this reference voltage, external devices have to pull down the line lower than Uref. Only in this case, Optii transmits this signal to the other bus. This is done to maintain the bi-directional behavior in all cases of I2C transmissions.

The resulting voltages during an imaginary transfer on the SCL lines are shown schematically in Figure 2.

Figure 2 Schematic Bus States

A more detailed view of one I2C-transducer is shown in Figure 3.

All four transducers are built analogically.

Figure 3 Optiis I2C-Transducer

In addition to the I2C lines Optii offers two test pins for general purposes, one in each direction. These test pins are unidirectional signal lines. The inputs detect high level at about 0,85 V. The outputs are open-drain outputs pulled up by a 10 kOhm resistor.

Figure 4 Test Pin Configuration