Using transceiver between DALI and microcontroller

Question

Does anyone have experience using a transceiver between a microcontroller and DALI bus? Please see the attached wiring diagram. I am not sure what is wrong with the circuit, but when I measure the voltage on the DALI bus, I get a reading of 18.5VDC, which is within the expected range of 16-22VDC. However, when I connect the positive or negative terminal to the MAX485 transceiver, the voltage drops to 3VDC?

#include <Dali.h>

void setup() {
Dali.begin(0, 1);
}

void loop() {
Dali.sendCmd(1, Dali.CMD_UP);
delay(1000);
}

Answer 1

MAX485 is an RS-485 transceiver.

DALI is not an RS-485 bus and not in any way compatible with an RS-485 bus, because it's a DALI bus.

There is no way connecting DALI bus to a MAX485 in any way can achieve anything useful.

Your diagram also connects the 18V DALI bus to MAX485 DE and DI pins, which make no sense and just damages the MAX485 chip.