I use RS485-TTL interface with buffer CD4069. Like this: SCM TTL to RS-485 Interface Module - ProtoSupplies but from aliexpress. I tried 2 interfaces.
It's not working because arduino receives bad signal on RX. When bypassing buffer directly from MAX485 it works. I checked with oscilloscope that signal directly from MAX485 and from buffer before I connect to arduino is same, but gets weaker and looks distorted when I connect signal from buffer to RX. Any idea why?
Voltage measured with DMM on RX is 2.3V when connected from MAX485 and 3.3V when connected from buffer.
Signal from buffer before I connected to RX (same is directly from MAX485 connected and not connected to RX)
Signal from buffer after I connected to RX