HC-12 2-Way Comms to light LEDs only works one way

Projects Networking, Protocols, and Devices
1

I am working on a simple project. Press a button on unit A and unit B lights up a LED for the duration of the button press (momentary), and vise versa. I have only been able to get them to work in one direction. I have figured out the last unit to power up is the one able to receive the signal and light up i.e. power up unit A then unit B, only B will light up. I am new to Arduino and can't for the life of me figure this out.

Each unit is an Arduino Nano with and HC-12, LEDs /w resistors, and a switch with a pulldown resistor and running the same sketch.

Any help would be amazing.

#include <SoftwareSerial.h>

SoftwareSerial HC12(10, 11); // HC-12 TX Pin, HC-12 RX Pin

int button = 2;
int led = 6;
boolean onOff = 0;



void setup() {
  pinMode (button, INPUT);
  pinMode (led, OUTPUT);
  Serial.begin(9600);             // Serial port to computer
  HC12.begin(9600);               // Serial port to HC12
}

void loop() {

  int buttonState = digitalRead(button);//read button state
  
  if(buttonState == 1){//if button is down
    HC12.println(1111);//send unique code to the receiver to turn on.
    onOff = 1;//set boolean to 1
  }
  if(buttonState == 0 && onOff == 1){//Verifier to send off signal once
    HC12.println(2222);//send unique code to the receiver to turn off. In this case 2222
  }



    if(HC12.available() > 1){    
    int input = HC12.parseInt();//read serial input and convert to integer (-32,768 to 32,767)    
    
    if(input == 1111){//if on code is received
      digitalWrite(led, HIGH);//turn LED on
    }
    if(input == 2222){//if off code is received
      digitalWrite(led, LOW);//turn LED off
    }
    }
       
  
  delay(20);

}
2

You have taken steps to ensure that the "off signal" is sent only once - at the moment the button is released - this is correct. It would be even more correct to send the "on signal" only once too - only at the moment the button pressed. You can use the same onOff flag for it.

Sending codes as 4-chars strings and reading them with parseInt() function is definitely a bad idea. It would be much faster to send only one byte code and read them simply with the read() command.

3

b707 thank you for your reply. I am new at this so bear with me.

If I enter the onOff flag, will the just send one signal, or will it be continuous as long as the button is held?

For sending the code, do I just replace parseInt with read, then reduce the characters being sent in the code?

Thank you!

4

you are using the SoftwareSerial library which has the restriction It cannot transmit and receive data at the same time. - this may be part of your problem
you could try AltSoftSerial

5

I think you can change the algorithm and send one signal for turning the LED on and one for off.

If you replaced the 4-digit char code by one byte, you will be able to read it with a single read() command.

6

Thank you horace. I tried AltSoftSerial and I get nothing at all now. I am at a loss

#include <AltSoftSerial.h>

AltSoftSerial HC12(2, 3); // HC-12 RX=2, TX=3

int button = 8;
int led = 6;
boolean onOff = 0;

void setup() {
  pinMode (button, INPUT);
  pinMode (led, OUTPUT);
  Serial.begin(9600);             // Serial port to computer
  HC12.begin(9600);               // Serial port to HC12
}

void loop() {

  int buttonState = digitalRead(button);//read button state
  
  if(buttonState == 1){//if button is down
    HC12.println(1);//send unique code to the receiver to turn on.
    onOff = 1;//set boolean to 1
  }
  if(buttonState == 0 && onOff == 1){//Verifier to send off signal once
    HC12.println(2);//send unique code to the receiver to turn off. In this case 2222
  }

    if(HC12.available() > 1){    
    int input = HC12.parseInt();//read serial input and convert to integer (-32,768 to 32,767)    
    
    if(input == 1){//if on code is received
      digitalWrite(led, HIGH);//turn LED on
    }
    if(input == 2){//if off code is received
      digitalWrite(led, LOW);//turn LED off
    }
    }
       
  
  delay(20);

}
7

there appears to be a problem using nano pins 2 and 3 with altSoftSerial
ran following program using altSoftSerial on a nano

// AltSoftSerial transmit/Receive Test
//
// Transmit data with Serial1 and try to receive
// it with AltSoftSerial.  You must connect a wire
// from Serial1 TX to AltSoftSerial RX.

#include <AltSoftSerial.h>

AltSoftSerial altser(9,8);
const int mybaud = 9600;

// Board            Serial1 TX   AltSoftSerial RX
// -----            ----------   ----------------
// UNO                   9              8
// Teensy 3.x            1              20
// Teensy 2.0            8 (D3)         10 (C7)
// Teensy++ 2.0          3 (D3)          4 (D4)
// Arduino Leonardo      1              13
// Arduino Mega         18              48

// Serial1 on AVR @ 16 MHz minimum baud is 245
// Serial1 on Teensy 3.2 @ 96 MHz minimum baud is 733

void setup() {
  delay(200);
  Serial.begin(115200);
  while (!Serial) ;  // wait for Arduino Serial Monitor
  altser.begin(mybaud);   // to AltSoftSerial RX
  Serial.println("AltSoftSerial transmit/ Receive Test");
}

void loop() {
  // transmit a test byte on Serial 1
  if (Serial.available() > 0) {
    altser.write(Serial.read());
  }
  // attempt to receive it by AltSoftSerial
  if (altser.available() > 0) {
    Serial.write(altser.read());
  }
}

note the pins used

AltSoftSerial altser(9,8);

running the above program and connecting pins 8 and 9 ran a loopback test OK
text entered on the serial monitor appears on the display, e.g.

AltSoftSerial transmit/ Receive Test
test 1
test 2 abcdefgh
resr 3 0987654321

Note - using pins 2 and 3 with the above program did not work
suggest changing your program to using pins 8 and 9

8

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