RS485 Code Question

Projects Programming
1

In this example for receiving data via RS485 with an expansion shield, what are they doing with this part of the code?

// receive data
digitalWrite(EN, LOW);//Enable Receiving Data
val = Serial.read();
if (-1 != val) {
if ('A' == val) {
digitalWrite(ledPin, HIGH);
delay(500);
digitalWrite(ledPin, LOW);
delay(500);

int ledPin = 13;
int EN = 2;
int val;

void setup()
{
pinMode(ledPin, OUTPUT);
pinMode(EN, OUTPUT);
Serial.begin(19200);
}

void loop()
{
// receive data
digitalWrite(EN, LOW);//Enable Receiving Data
val = Serial.read();
if (-1 != val) {
  if ('A' == val) {
    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    delay(500);
  }
}
}
2

What's your interpretation?

3

I don't understand the code yet but the shield or UNO may be waiting for a message to set it to receive mode. I'm not a code guru yet, so I don't understand what this means: ```
if (-1 != val) {
if ('A' == val)

4

Ok, these are two comparison operators.

"==" means "is the expression to the left of the operator equal to the expression on the right?"

"!=" means "is the expression to the left of the operator not equal to the expression on the right?"

5

are you confused at the order they are compared or in general about the == and !=