TTL comport comms?

Hello Guys,

I've managed to communicate over a MODBUS protocol (modbus.h library) and it works fine over the USB connection to COMport x on my PC.

However i want to communicate over the serial port pin 0 and 1 on TTL. (use TTL to 485 converter, bit of cable, then back from 485 to USB) on comport y.

When i use the USB port on the arduino and have comms, and put a scope meter on the serial communications i read all the information so i know comms via pin 0 and 1 works. also all my converters work fine when i write a test program to send a string to the PC over 485 (not in modbus mode).

My problem is that i can't establish communications without the USB. my goal is a stand alone arduino with power supply and comms over the TTL lines to 485. do i need to include specific code to get the channel open on the pins 0 and 1?

#include <modbus.h>
#include <modbusDevice.h>
#include <modbusRegbank.h>
#include <modbusSlave.h>
#include <SoftwareSerial.h>

Add more registers if needed
Digital input pins 2
Digital output pins 8
Analog output pins 9 (PWM)
Analog input pins 0

  modbusDevice SCADA;
  modbusSlave PLC;

char string1[] = "4354";

//Defining PIN inputs and outputs
int DigitalInput_1 = 2,
    DigitalOutput_1 = 8,
    AnalogInput_1 = A0,
    PWMOutput_1 = 9;

//Defining storing variable
int DO1, DI1;
word AI1;
byte AO1;
int value;

void setup()
  SCADA.setId(10); ///Set PLC ID

//Add Digital Input registers

// Add Digital Output registers

//Analog input registers

//Analog Output registers

  PLC._device = &SCADA;  


  pinMode(AnalogInput_1, INPUT);

  pinMode(PWMOutput_1, OUTPUT);

void loop(){
  //Digital Input

        DI1 = digitalRead(DigitalInput_1); // was een byte
    if (DI1 >= 1)SCADA.set(10001,1);
    if (DI1 <= 0)SCADA.set(10001,0);

  //Digital output
          DO1 = SCADA.get(00001);
      if (DO1 <= 0 && digitalRead(DigitalOutput_1) == HIGH)digitalWrite(DigitalOutput_1,LOW);
      if (DO1 >= 1 && digitalRead(DigitalOutput_1) == LOW)digitalWrite(DigitalOutput_1,HIGH);
  //Analog input

    AI1 = analogRead(AnalogInput_1);
    AI1 = map (AI1, 0, 1024, 0, 100);
    SCADA.set(30001, (word) AI1);
    SCADA.set(30002, (int) value);

  //Analog output 
    AO1 = SCADA.get(40001);
    AO1 = map (AO1, 0, 20, 0, 255);

Depending on the model of Arduino you use it might work without a code change. Some models (p.e. Leonardo) need a change in the library. If you use the standard Arduino UNO and it doesn't work, post the wiring schemata you use.