1.2 DALI Interface

DALI Interface circuit handles the communication between the MCU and the DALI bus.

Following the DALI protocol, the DALI bus carries a differential signal, the DALI interface circuit transfer the communication between the MCU and DALI bus.

The DALI bus is differential pair, to avoid the risk of sharing common ground, the DALI interface circuit is isolated with the MCU part via two optocouplers. The repetitive peak isolation voltage of these two optocouplers reached 890V as described in datasheet.

For decoding, the DALI interface uses constant current source to provide a stable power supply for the comparator MIC834. As its internal stable reference, the output of comparator depends on the regular input. The output signal drives the optocoupler to transfer the signal to the MCU. For coding, the MCU drives the optocoupler directly to get the DALI bus modulated via a MOSFET.

All components on the board are designed with a high reliable consideration, which makes the system working stable within the temperature range from -40°C to +105°C.

Figure 1-3. DALI Interface
Figure 1-4. Schematic of the DALI Interface