Micro UART not communicating

Projects Networking, Protocols, and Devices
3

Your circuit looks fine to me.Try to do a loopback test in the MAX491 connecting the TX(9,10) pairs to the RX(12,11) pairs and send something using a Serial.println;
If all are ok you should get the signal back in the RX.
Something like this:

void setup() {
  // initialize both serial ports:
  Serial.begin(9600);
  Serial.print("Ping Pong");
}

void loop() {
  // read from port 1, send to port 0:
  if (Serial.available()) {
    char inByte = Serial.read();
    Serial.print(inByte); 
  }
}