[communication between two UART on Tiva C]

My 2 cents....try adding a 300-500ms delay before you start your loop. I have found that to solve a similar problem I was having, YMMV.

Tried - same abra-cadabra

[communication between two UART on Tiva C]

Running your code I got the following:

On Serial ttyACM0:

[communication between two UART on Tiva C]

I want to resend each character from one UART port to another.

Hardware: Lauchpad TivaC EK-TM4C123GXL.

First port is the default port that is connected to microUSB on the board.

The second port is UART2 (Rx = PD6; Tx = PD7) connected to DB9 through MAX3232:. Power is VBUS - GND.

DB9 is now connected to computer through RS232-USB adapter.

I communicate with 1st serial port through serial monitor in Energia (ttyACM0).

I communicate with 2nd serial port through serial terminal in Linux (ttyUSB0). 

Code is very simple:

void setup() {
  // initialize ports:
  Serial.begin(9600); //connected with USB
  delay(100);
  Serial2.begin(9600); //RS232: Rx = PD6; Tx = PD7
  delay(100);
}

void loop() {
}

void serialEvent() {
  while (Serial.available()) {
    // get the new byte:
    char inChar = (char)Serial.read();
    //send it to RS232
    Serial2.print(inChar); 
  }
  while (Serial2.available()) {
    // get the new byte:
    char inChar = (char)Serial2.read();
    //send it to UI
    Serial.print(inChar); 
  } 
}

I got the following:

Then I send something from Energia serial monitor (serial) - this message is displayed in linux serial terminal (serial2) - this is all good.

Another way (from Serial2 to Serial) it does not work - I send messages from linux terminal, but nothing changes in Energia serial monitor.

 

What is wrong with my setup?