@Lars-Tobias-Skjong-Børsting said in Connect Omega 2 to UART tx1 and rx1 using Mini Dock: I have this TTL UART to RS-485 board: https://www.aliexpress.com/item/5PCS-MAX485-RS-485-Module-TTL-to-RS-485-module-Raspberry-pi/32579369267.html I think your module is same or very similar like this: MAX485 MODULE RS-485 TO TTL CONVERTER so it is not designed for Raspberry Pi. On Omega2 at least at the RO pin of MAX485 some kind of 5V to 3.3V level shifting is needed. The simplest solution: put a voltage divider between RO and RX1. And you should connect the pull-up resistors of input pins (DI, DE, RE) to 3.3V. RS-485 can be made full-duplex by using four wires ie. two twisted pairs. Is your Modbus slave full-duplex? BTW you could build also full duplex config with two of your MAX485 modules.