I bought an uart ttl to usb 2.0 adapter on ebay which I tried out yesterday with no luck. I measured all the pins and found to my surprise that the RX pin actually carries 3.3V. This can’t be right as the unit I intend to communicate with has 5V on its TX and 0V on its RX. Can my adapter be dysfunctional?
Secondly, I wonder if it doesn’t matter that one seem to carry 3.3V on its TX and the other 5V, can the respective devices handle this in any cases or must it be carefully matched?