problem in using message received by 433mhz receiver

Projects Programming
1

I have use 433Mhz transmitter and receiver to send values of two sensors from transmitter to receiver. I am able to print the values received by receiver over serial monitor. But I want to blink an LED according to message received. I want to blink an LED when messages are "Pres" and "More". And else don't blink. What's wrong with my code??
Here is my code

Transmitter

#include <VirtualWire.h>

int ObstaclePin = 7;  // This is our input pin
int Obstacle = HIGH;  // HIGH MEANS NO OBSTACLE
const int AOUTpin=0;//the AOUT pin of the alcohol sensor goes into analog pin A0 of the arduino
const int DOUTpin=8;//the DOUT pin of the alcohol sensor goes into digital pin D8 of the arduino



int limit;
int value;
void setup()
{
  pinMode(ObstaclePin, INPUT);
  pinMode(DOUTpin, INPUT);
  Serial.begin(9600);
  vw_set_tx_pin(12); // Pin data
   // Initialize the IO and ISR
   vw_setup(2000); // Bits per sec

}
void loop()
{
  irsensor();
  delay(100);
  alcoholsensor();
}

void irsensor()
{  
  Obstacle = digitalRead(ObstaclePin);
    if (Obstacle == LOW)
  {
    Serial.println("obstacle absent");
    send("message =Abse");
  }
  else
  {
    Serial.println("obstacle present");
    send("message =Pres");
  }
}
void alcoholsensor()
{
  value= analogRead(AOUTpin);//reads the analaog value from the alcohol sensor's AOUT pin
limit= digitalRead(DOUTpin);//reads the digital value from the alcohol sensor's DOUT pin
Serial.print("Alcohol value: ");
Serial.println(value);//prints the alcohol value
Serial.print("Limit: ");
Serial.print(limit);//prints the limit reached as either LOW or HIGH (above or underneath)
delay(100);
if (limit == HIGH){
Serial.println("value is less");//if limit has been reached, LED turns on as status indicator
send("message =Less");
}
else{
Serial.println("value is more");//if threshold not reached, LED remains off
send("message =More");
}
}
  
void send (char *message)
{
    vw_send((uint8_t *)message, strlen(message));
    vw_wait_tx(); // Wait until the whole message has gone
}

Receiver code

/* 
2 SimpleReceive 
3 This sketch displays text strings received using VirtualWire 
4 Connect the Receiver data pin to Arduino pin 11 
5 */ 
 #include <VirtualWire.h> 
 byte message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages 
 byte messageLength = VW_MAX_MESSAGE_LEN; // the size of the message 
int Led=13;
 void setup() 
 { 
 Serial.begin(9600); 
 Serial.println("Device is ready"); 
 // Initialize the IO and ISR 
 vw_set_rx_pin(11);
 vw_setup(2000); // Bits per sec 
 vw_rx_start(); // Start the receiver
 pinMode(Led,OUTPUT); 
 } 
 void loop() 
 {
  receive1();
  decision1();
  decision2();
 }
 void receive1()
 { 
 if (vw_get_message(message, &messageLength)) // Non-blocking 
 { 
 Serial.print("Received: "); 
 for (int i = 0; i < messageLength; i++) 
 { 
 Serial.write(message[i]); 
 } 
 Serial.println(); 
 }
 }
 void decision1()
 {
 if(strcmp(message,  "Pres"))
   {
      digitalWrite(Led,HIGH);
   }
    else
    {
       digitalWrite(Led,LOW);
    }
 }
  void decision2()
  {
 if(strcmp(message, 'More'))
   {
      digitalWrite(Led,HIGH);
   }
    else
    {
       digitalWrite(Led,LOW);
    }
 }
2

There are at least three problems.

  1. the message you are sending is the string "message =More" but you are comparing the message received to the string "More".

  2. strcmp returns three different values, depending on the outcome of the comparison. ZERO is returned if the strings are identical.

if(strcmp(message, 'More'))
  1. use double quotes, not single quotes, to enclose a character string.
3 
the message you are sending is the string "message =More" but you are comparing the message received to the string "More".

Message have been received. I only want to blink an LED when message received is "Pres" and "More", without comparing.
Should I have to write it as

if(message, "Pres")
         {digitalWrite(Led,HIGH);}
4

You MUST do a comparison.

You can use strcmp(), but you need to learn how strcmp() works.

5

Strings are a minefield littered with the mangled corpses of decades of software developers. After you've gotten things working with strcmp (because that's a good exercise, to be honest), it's probably worth asking yourself the question: "Does this message really need to be a big string of human-readable characters, or might it just be a byte or two?" Because if the first goal of this message is to communicate something to another program as opposed to a human, sending text is likely to make things wayyy more complicated than they need to be. It's a gazillion times easier to check to see if a received byte represents a particular decimal number, or has certain bits set in it. It's almost certain to be much faster and less prone to dumb bugs that might result from things like doing case-sensitive string comparisons when you really don't care about case, wandering off and crashing (or behaving strangely) because your string didn't have a terminator where you thought it did, or had fewer characters than you expected, etc.

6

sorry. Now I have rewritten a correct code. But still LED is not working according to message.
Now, what's wrong with it??

here is my receiver code

/* 
2 SimpleReceive 
3 This sketch displays text strings received using VirtualWire 
4 Connect the Receiver data pin to Arduino pin 11 
5 */ 
 #include <VirtualWire.h> 
 byte message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages 
 byte messageLength = VW_MAX_MESSAGE_LEN; // the size of the message 
int Led=13;
 void setup() 
 { 
 Serial.begin(9600); 
 Serial.println("Device is ready"); 
 // Initialize the IO and ISR 
 vw_set_rx_pin(11);
 vw_setup(2000); // Bits per sec 
 vw_rx_start(); // Start the receiver
 pinMode(Led,OUTPUT); 
 } 
 void loop() 
 {
  receive1();
  decision1();
  decision2();
 }
 void receive1()
 { 
 if (vw_get_message(message, &messageLength)) // Non-blocking 
 { 
 Serial.print("Received: "); 
 for (int i = 0; i < messageLength; i++) 
 { 
 Serial.write(message[i]); 
 } 
 Serial.println(); 
 }
 }
 void decision1()
 {
 if(strcmp(message , "Pres")==0)
   {
      digitalWrite(Led,HIGH);
   }
    else
    {
       digitalWrite(Led,LOW);
    }
 }
  void decision2()
  {
 if(strcmp(message , "More")==0)
   {
      digitalWrite(Led,HIGH);
   }
    else
    {
       digitalWrite(Led,LOW);
    }
 }