Where am I going to wrong with Max458 TTL to RS485?

[bkeith1980]

Hello,
Im attempting to get two arduinos to communicate via RS485, I have a nano as the master and an uno as the slave. Im following a video that walks through it but its not working for me, ive tried several videos now. On the Nano im printing to a new line the letter A, when the letter A is seen by the Uno it should turn off an LED for 1 second. Some trouble shooting steps ive taken are making sure that every pin is properly connected and that all wries are in the correct spot. Below is my master code:

#define MASTER_EN 8

void setup() {
  
  Serial.begin(9600);
  pinMode(MASTER_EN, OUTPUT);
  digitalWrite(MASTER_EN, HIGH);
}

void loop() {

  digitalWrite(MASTER_EN, HIGH);
  delay(100);
  Serial.println('A');
  Serial.flush();
  digitalWrite(MASTER_EN, LOW);
  delay(1000);
}

Here is my slave code:

#define LED 12
#define SLAVE_EN 8

void setup() {

  digitalWrite(LED, OUTPUT);
  digitalWrite(SLAVE_EN, OUTPUT);
  Serial.begin(9600);
  digitalWrite(SLAVE_EN, LOW);
}

void loop() {

  while(Serial.available()) {
    if(Serial.read() == 'A') {
      digitalWrite(LED, HIGH);
    }
  }
}

Here is my wiring diagram, note, I am not using a button, my code is basically a combo of two or more that I found online:

Here are a few pictures of my current setup incase anyone sees anything obvious that I may be missing:
Both:

Slave:

Master:

Is there an easier way to do this? I feel like im missing something. Im building an ROV and have finished everything I want on the ROV but I used I2C for that. I need to figure out how to rewrite the code using RS485 protocol if I want to get to depth. Let me know if have any good tutorials because im not finding much. Thanks again!

[Paul_KD7HB]

@bkeith1980

Serial.println('A');

This sends the "A" plus a carriage return and a line feed. So, three characters. Your receive is only reading one character. Why the difference?
Try using just Serial.print('A');

[kmin]

@bkeith1980

when the letter A is seen by the Uno it should turn off an LED for 1 second.

In you code it's not like this. It's turning led on and leaving it on.

[jim-p]

@bkeith1980

I feel like im missing something.

The GND of the two RS485 boards need to be connected together.
LED is on pin 13 NOT 12