How to read binary correctly?

[dhary-1]

I have a project that consists of 2 Arduinos as a transmitter and a receiver. I have no problem at the transmitter Arduino, but my problem is at the receiver, where I get input as a binary sequence of 4 bits and translate them using an if-else statement. The problem is that when reading the binary at the if-else statement, I have interference between the second and first statements; when Orange LED is supposed to be HIGH, I have Orange and Red alternating between HIGH and LOW; this also happens when Yellow is supposed to be HIGH; I have Yellow and Green alternating between HIGH and LOW. I figured that this happens because the first bit at the orange and red are both 0, and at the yellow and green are both 1. But I don't know how to solve this problem, and read the whole 4 bits before making a decision? Help please.

const int RED_LED_PIN = 2;
const int ORANGE_LED_PIN = 3;
const int YELLOW_LED_PIN = 4;
const int GREEN_LED_PIN = 5;
const int INPUT_PIN = 8;

void setup() {
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(ORANGE_LED_PIN, OUTPUT);
  pinMode(YELLOW_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(INPUT_PIN, INPUT);
}

void loop() {
  byte receivedData = 0 ;

  for (int i = 0; i < 4; i++) {
    receivedData |= digitalRead(INPUT_PIN) << i;
    delay(10);
  }

  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(ORANGE_LED_PIN, LOW);
  digitalWrite(YELLOW_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, LOW);

if (receivedData == 0b0000) {
  digitalWrite(RED_LED_PIN, HIGH);
  digitalWrite(ORANGE_LED_PIN, LOW);
  digitalWrite(YELLOW_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, LOW);
} 
else if (receivedData == 0b0110) {
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(ORANGE_LED_PIN, HIGH);
  digitalWrite(YELLOW_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, LOW);
} 
else if (receivedData == 0b1001) {
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(ORANGE_LED_PIN, LOW);
  digitalWrite(YELLOW_LED_PIN, HIGH);
  digitalWrite(GREEN_LED_PIN, LOW);
} 
else if (receivedData == 0b1111) {
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(ORANGE_LED_PIN, LOW);
  digitalWrite(YELLOW_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, HIGH);
}

  delay(100);
}

[JCA34F]

Do you have a 10k pulldown resistor connected from pin 8 to GND to keep the pin from floating HIGH, LOW, HIGH, LOW when the button is not pressed?

[dhary-1]

No, i didn't use any resistor between pin 8 to GND before, but after your comment i just did and nothing happens. FYI I'm using Tinkercad.

[Paul_KD7HB]

@dhary-1

But I don't know how to solve this problem, and read the whole 4 bits before making a decision?

Why did you create the problem when standard serial communications is available for both Arduinos.

[dhary-1]

I don't know how to measure the pulses length actually.

Here is the transmitter code:

const int TRIGGER_PIN = 12;
const int ECHO_PIN = 11;
const int OUTPUT_PIN = 10;

void setup() {
  pinMode(TRIGGER_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(OUTPUT_PIN, OUTPUT);
}

void loop() {
  digitalWrite(TRIGGER_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIGGER_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH);
  int distance = duration * 0.034 / 2;
  int percentage = map(distance, 30, 200, 100, 0);
  percentage = constrain(percentage, 0, 100);

  byte binaryOutput;

  if (percentage >= 0 && percentage <= 9) {
    binaryOutput = 0b0000;
  } else if (percentage >= 10 && percentage <= 24) {
    binaryOutput = 0b0110;
  } else if (percentage >= 25 && percentage <= 49) {
    binaryOutput = 0b1001;
  } else if (percentage >= 50 && percentage <= 100) {
    binaryOutput = 0b1111;
  }

  for (int i = 0; i < 4; i++) {
    digitalWrite(OUTPUT_PIN, bitRead(binaryOutput, i));
    delay(10);
  }

  delay(100);
}

[dhary-1]

Because I will modulate and transmit the output through a channel from the first Arduino until it reaches the second, that's why I can't use conventional methods.

[gcjr]

@dhary-1

  for (int i = 0; i < 4; i++) {
    receivedData |= digitalRead(INPUT_PIN) << i;
    delay(10);
  }

looks like you want to read a 4 bit sequence.
i'll assume you expect bits to be 10 msec apart

how do you know when the sequence starts? is there a start bit what is always the opposite state of the input than the state of the start bit?

how do you synchronize receiving data to the transmission data? do you repidly (more frequently than every 10 msec) to recognize the start bit and then delay for 5 msec to read the first bit and then delay by 10 msec for every following bit?

isn't there a device on the chip that alread does this?

[dhary-1]

I didn't write the code myself; I'm so bad at writing codes, I have copied it from ChatGPT.

[dhary-1]

I'm trying to build two separate devices connected by a powerline cable, the output from the transmitter Arduino will be received at the receiver Arduino.

In the Tinkercad simulation, I have simply connected the output from the transmitter to the input at the receiver without going into the details of the modulation, channel, and de-modulation process.

[dhary-1]

@Delta_G

Do you think following some tutorials might work a little better?

What you're doing is kind of complex. Just stick with Serial for now. You're not up to re-inventing it.

Start simple and learn the basics before you go jumping off in the deep end and start asking people for advise that you won't even understand when they give it to you.

You're absolutely right! But unfortunately I can't drop it since it's a part of my senior design project and I didn't realize this problem until now.

[dhary-1]

@Delta_G

@dhary-1

powerline cable,

Are you trying to communicate through the electrical socket?

Yes

[gcjr]

@dhary-1

Yes

i'm curious, what is the modulated signal injected onto the power line?

[dhary-1]

@gcjr

@dhary-1

Yes

i'm curious, what is the modulated signal injected onto the power line?

Actually, it's not really injected; it'll be ASK modulated and added using an op-amp with the power signal to the channel as a start. Injection into the powerline is the next step for the project.

[dhary-1]

@Delta_G

@dhary-1

But unfortunately I can't drop it since it's a part of my senior design project and I didn't realize this problem until now.

I'm telling you now that the path you're on will take longer than stopping for a day and covering some tutorials and learning at least the basics.

That will get you there faster than struggling with forum posts you can't understand.

If that is faster, and you say you don't have time for that, then it sounds like you're in a pretty bad spot. If you don't have time to do it the faster way, how will you ever get it done the slow hard way?

Thank you for your advice, I'll stop and cover the basics if it will give me better results than this method. Really appreciate your help.

[dhary-1]

@Delta_G

@dhary-1

Yes

Then what you're doing won't work. You're so far from what will work that I am not sure what even to tell you.

Have a look at the X-10 protocol. I have a non-blocking library for X-10 on my GitHub but it isn't particularly well documented and would have to be manually installed.

I have tested the modulation and de-modulation of a random binary signals using ASK modulation through a powerline with 60Hz power running through it and I have succeeded. This is not a problem at all now. It's true that I have faced some problems injecting the message into the powerline but I have changed my plan to add it with the power line for a start, and then I will look more into the actual injection of the message.
Also, thank you for your advice about X-10.

[dhary-1]

@Delta_G

Please don't take this the wrong way. I'm not trying to dissuade you. Only to try to convince you to do something that will help you actually accomplish this and not just fail.

If you can't understand what that for loop I quoted earlier does, then you have no hope ever of doing what you describe. That will be orders of magnitude more complicated than just understanding how some 10ms pulses got generated.

I understand you, thank you so much for your help.

[gcjr]

@dhary-1

I have tested the modulation and de-modulation of a random binary signals using ASK modulation through a powerline with 60Hz power running through it and I have succeeded.

why can't you use a tone detector on the receive side and feed it's output into the RX of a UART and similarly use a tone generator on the transmit side driven by the TX side of a UART on the chip?

[alto777]

@gcjr

why can't you use a tone detector

If @dhary-1 can reliably see bits on both sides, why bother using a tone generator and detector?

Or is this already part of what is going on:

@dhary-1

Because I will modulate and transmit the output through a channel

@dhary-1 please elaborate on your power line modulator/demodulator scheme. As suggested, if you have a power line modem, in effect, the easy thing to do is use serial comms between the Arduinos.

a7

[dhary-1]

@gcjr

@dhary-1

I have tested the modulation and de-modulation of a random binary signals using ASK modulation through a powerline with 60Hz power running through it and I have succeeded.

why can't you use a tone detector on the receive side and feed it's output into the RX of a UART and similarly use a tone generator on the transmit side driven by the TX side of a UART on the chip?

I don't think I need a tone detector and generator, but UART might work since my problem is receiving the binary sequence and getting back each single bit alone to determine the state of each LED.

[gcjr]

@dhary-1

I don't think I need a tone detector and generator

you said amplitude shift keying (ASK) modulation