RS485 to TTL, serial output giving only -1

Hello, I am trying to read in data from modbus rs485 rtu to my arduino mega and output in my PC serial monitor. However, the only thing that outputs is -1. Any guidance is always appreciated.

I have the RS485 to TTL converter found here RS422 / RS485 to TTL Converter / TTL Repeater (Industrial) – CommFront connected to a pressure transmitter that outputs rs485, RTU. My current wiring diagram is as follows (sorry for the bad drawing).

My code is as follows

int b = 0;

void setup() 
{
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
  Serial1.begin(9600); // open serial port1 for reading in (rx1, tx1 pins)
  Serial.println("Starting!");
  
}

void loop() {
if (Serial1.available() > 0) {  //check serial1 port, if i comment out this if statement thats how i get -1
  Serial.println("The data recievied is: ");
 
  b = Serial1.read();
  Serial.println(b);
 }
}

What you linked can do both RS-422 and 485 so I’m going to guess how it works, but it is just a guess.

ron_sutherland: What you linked can do both RS-422 and 485 so I'm going to guess how it works, but it is just a guess.

|500x455

Thats exactly what the converter is. I will give that diagram a shot tomorrow! Thank you!