I’m trying to establish a serial communication with an audio recorder remote port with the hardware serial TX and RX from an Arduino Uno. But I’ve got a real problematic response from the recorder’s remote port TX to the RX from the Arduino. Even the logic analyser can’t make anything out of it. But If I disconnect the RX connection on the Arduino (port 0) the signal becomes clear on the logic analyser. The remote port has an 3.3V line, and the logic levels are also 3.3V. I’ve powered the Arduino with the same 3.3V (on the 5V port). Everything seems to work fine, except for receiving signals (no problem talking to the remote port).
Now I’ve put an HC4050 non inverting buffer between it (powered by the same 3.3V) and finally it works. But in the final schematic I rather leave as much unused components out of it. So, why do I need to put the signal trough the buffer? Is the signal too weak and needs it a boost?
If I look at the UNO schematic, the RX /TX ports from the UNO are connected to an Atmega16U2 trough a resistor. I expect this is interfering with the remote communication. I’m I right? Will this problem probably solve itself if I use the Atmega328 standalone?