I have a problem with communication via Modbus RTU. First of all sorry for my English ;): I’m using RS485 Pi SN65HVD72 to connect with MultiCONT PRD-28-2. I made everything like is in this instruction: https://www.abelectronics.co.uk/kb/article/1035/raspberry-pi-3-serial-port-usage config.txt changes: toverlay=pi3-miniuart-bt enable_uart=1 After this steps the config of my /dev looks like this: lrwxrwxrwx 1 root root 7 gru 30 15:03 serial0