I have a V3 nano and trying to use the uart pins to send serial to my Arduino nano RX pin, but to no avail. I have it working with USB connection but I'd prefer using the pins as it will all be PCB mounted. I tried a loopback test on the uarts (linking the tx to rx) on the PCduino and this works fine.
My initial attempt was to connect the tx pin on the PCduino directly to my Arduino nano RX, (since it'll be 3.3v into my Arduino, shouldn't be a problem). I didn't get any response on the Arduino at all when sending from the PCduino serial monitor in the IDE. I then tried connecting the rx pin to the tx on my Arduino through the Linksprite voltage converter shield. Still doesn't work . Truth is I don't need to send anything from the Arduino to the PCduino anyway.
I can confirm if I send serial through the serial monitor using USB the Arduino does receive it.