I have a problem making an RS485 communication between an Arduino and a power meter work. I've ordered a RS485 to TTL converter and have checked that it is working using the RS232 spare port on my STK500 board and a python program using the minimodbus library. Since I did not manage to get a connection with the Arduino Uno, I tried to communicate with the power meter using the passthrough serial Console on my PC like I did with the STK500, but I did not get a valid response. Is my assumption that this should work just as fine as using the STK500 board wrong? What can I do to trouble shoot? I unfortunately only have a very old analogue oscilloscope, but at least I was able to confirm that the Serial port of the arduino is sending out data. If I connect RX and TX, the minicom serial console shows that I can communicate with myself. However, I'm unable to get a bidirectional communication between the Uno and the STK500 RS232 port.